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Sample records for electron-deficient double bonds

  1. Heteroarene-Directed Oxidative sp(2) C-H Bond Allylation with Aliphatic Alkenes Catalyzed by an (Electron-Deficient η(5)-Cyclopentadienyl)rhodium(III) Complex.

    PubMed

    Takahama, Yuji; Shibata, Yu; Tanaka, Ken

    2016-06-17

    It has been established that the oxidative sp(2) C-H bond allylation with aliphatic alkenes proceeds under mild conditions by using heteroarenes as directing groups and an (electron-deficient η(5)-cyclopentadienyl)rhodium(III) complex, [Cp(E)RhCl2]2, as a precatalyst. In sharp contrast, the use of [Cp*RhCl2]2 instead of [Cp(E)RhCl2]2 led to a complex mixture of products under the same reaction conditions. PMID:27227320

  2. Bridging gold: B-Au-B three-center-two-electron bonds in electron-deficient B(2) Au(n) (-/0) (n = 1, 3, 5) and mixed analogues.

    PubMed

    Yao, Wen-Zhi; Li, Da-Zhi; Li, Si-Dian

    2011-01-30

    A systematic density functional theory and wave function theory investigation on the geometrical and electronic structures of the electron-deficient diboron aurides B(2) Au n-/0 (n = 1, 3, 5) and their mixed analogues B(2) H(m) Au n- (m + n = 3, 5) has been performed in this work. Ab initio theoretical evidences strongly suggest that bridging gold atoms exist in the ground states of C(2v) B(2) Au(-) ((1) A(1) ), C(2) B(2) Au 3-((1) A), C(2v) B(2) Au(3) ((2) B(1) ), C(2v) B(2) Au 5-((1) A(1) ), and C(s) B(2) Au(5) ((2) A″), which all prove to possess a B-Au-B three-center-two-electron (3c-2e) bond. For B(2) H(m) Au n- (m + n = 3, 5) mixed anions, bridging B-Au-B units appear to be favored in energy over bridging B-H-B, as demonstrated by the fact that the Au-bridged C(2v) B(2) H(2) Au(-) ((1) A(1) ), C(s) B(2) HAu 2- ((1) A'), and C(1) B(2) HAu 4- ((1) A) lie clearly lower than their H-bridged counterparts C(s) B(2) H(2) Au(-) ((1) A'), C(2) B(2) HAu 2- ((1) A), and C(2v) B(2) HAu 4- ((1) A(1) ), respectively. Orbital analyses indicate that Au 6s makes about 92-96% contribution to the Au-based orbitals in these B-Au-B 3c-2e interactions, whereas Au 5d contributes 8-4%. The adiabatic and vertical detachment energies of the concerned anions have been calculated to facilitate their future experimental characterizations. The results obtained in this work establish an interesting 3c-2e bonding model (B-Au-B) for electron-deficient systems in which Au 6s plays a major role with non-negligible contribution from Au 5d. PMID:20652871

  3. Valence State Driven Site Preference in the Quaternary Compound Ca5MgAgGe5: An Electron-Deficient Phase with Optimized Bonding

    SciTech Connect

    Ponou, Simeon; Lidin, Sven; Zhang, Yuemei; Miller, Gordon J.

    2014-04-18

    The quaternary phase Ca5Mg0.95Ag1.05(1)Ge5 (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma – Wyckoff sequence c12 with a = 23.1481(4) Å, b = 4.4736(1) Å, c = 11.0128(2) Å, V = 1140.43(4) Å3, Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R2+nT2X2+n, previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm – Wyckoff sequence f5c2. The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO electronic structure calculations indicate electronic stabilization and overall bonding optimization in the polyanionic network. Other stability factors beyond the Zintl concept that may account for the electronic stabilization are discussed.

  4. Understanding Rotation about a C=C Double Bond

    ERIC Educational Resources Information Center

    Barrows, Susan E.; Eberlein, Thomas H.

    2005-01-01

    The study focuses on the process and energetic cost of twisting around a C=C double bond and provides instructors with a simple vehicle for rectifying the common misrepresentation of C=C double bonds as rigid and inflexible. Discussions of cis and trans isomers of cycloalkenes are a good entry point for introducing students to the idea of a…

  5. Models for incomplete nucleophilic attack on a protonated carbonyl group and electron-deficient alkenes: salts and zwitterions from 1-dimethylamino-naphthalene-8-carbaldehyde.

    PubMed

    Lari, Alberth; Pitak, Matuesz B; Coles, Simon J; Rees, Gregory J; Day, Stephen P; Smith, Mark E; Hanna, John V; Wallis, John D

    2012-10-14

    The X-ray crystal structures of salts and zwitterionic Knoevenagel products from 1-dimethylamino-naphthalene-8-carbaldehyde show long N-C bonds between peri-groups which provide models for incomplete nucleophilic attack on a protonated carbonyl group and electron-deficient alkenes respectively. For the salts the N-C bonds lie in the range 1.625-1.638 Å with C-OH bonds intermediate in length between single and double bonds, while for the zwitterions the N-C bonds lie in the range 1.612-1.660 Å. The structural assignment of the former is supported by solid state (13)C and (15)N NMR studies on doubly isotopically-labelled material. Several zwitterions were converted to naphtha[1,8-bc]azepines by a mechanism involving the tertiary amino effect. PMID:22910881

  6. [Cu(NHC)]-Catalyzed C-H Allylation and Alkenylation of both Electron-Deficient and Electron-Rich (Hetero)arenes with Allyl Halides.

    PubMed

    Xie, Weilong; Chang, Sukbok

    2016-01-26

    New reactivity of a [Cu(NHC)] (NHC=N-heterocyclic carbene) catalyst is disclosed for the efficient C-H allylation of polyfluoroarenes using allyl halides in benzene at room temperature. The same catalyst system also promotes an isomerization-induced alkenylation of initially the generated allyl arenes when the reaction is run in tetrahydrofuran. Significantly, not only electron-deficient but also electron-rich (hetero)arenes undergo this double-bond migration process, thus leading to alkenylated products. The present system features mild reaction conditions, broad scope with respect to the arene substrates and allyl halide reactants, good functional-group tolerance, and high stereoselectivity. PMID:26695120

  7. Stress analysis of adhesive bonded stiffener plates and double joints

    NASA Technical Reports Server (NTRS)

    Yuceoglu, U.; Updike, D. P.

    1975-01-01

    The general problem of adhesive bonded stiffener plates and double joints of dissimilar orthotropic adherends with transverse shear deformations are analyzed. Adhesive layers are assumed to be of an isotropic, elastic and relatively flexible material. It is shown that the stress distributions in the adhesive layers are very much dependent on the bending deformations in adherends. Also, it is found that, in the adhesive layer, maximum transverse normal stress is, in many cases, larger than the longitudinal shear stress and that both occur at the edge of the joint. The general method of solution developed is applied to several practical examples.

  8. A Simple Visualization of Double Bond Properties: Chemical Reactivity and UV Fluorescence

    ERIC Educational Resources Information Center

    Grayson, Scott M.

    2012-01-01

    A simple, easily visualized thin-layer chromatography (TLC) staining experiment is presented that highlights the difference in reactivity between aromatic double bonds and nonaromatic double bonds. Although the stability of aromatic systems is a major theme in organic chemistry, the concept is rarely reinforced "visually" in the undergraduate…

  9. The sEDA(=) and pEDA(=) descriptors of the double bonded substituent effect.

    PubMed

    Mazurek, Andrzej; Dobrowolski, Jan Cz

    2013-05-14

    New descriptors of the double bonded substituent effect, sEDA(=) and pEDA(=), were constructed based on quantum chemical calculations and NBO methodology. They show to what extent the σ and π electrons are donated to or withdrawn from the substituted system by a double bonded substituent. The new descriptors differ from descriptors of the classical substituent effect for which the pz orbital of the ipso carbon atom is engaged in the π-electron system of the two neighboring atoms in the ring. For double bonded substituents, the pz orbital participates in double bond formation with only one external atom. Moreover, the external double bond forces localization of the double bond system of the ring, significantly changing the core molecule. We demonstrated good agreement between our descriptors and the Weinhold and Landis' "natural σ and π-electronegativities": so far only descriptors allowing for evaluation of the substitution effect by a double bonded atom. The equivalency between descriptors constructed for 5- and 6-membered model structures as well as linear dependence/independence of the constructed parameters was discussed. Some interrelations between sEDA(=) and pEDA(=) and the other descriptors of (hetero)cyclic systems such as aromaticity and electron density in the ring and bond critical points were also examined. PMID:23532500

  10. Double pancake bonds: pushing the limits of strong π-π stacking interactions.

    PubMed

    Cui, Zhong-hua; Lischka, Hans; Beneberu, Habtamu Z; Kertesz, Miklos

    2014-09-17

    The concept of a double-bonded pancake bonding mechanism is introduced to explain the extremely short π-π stacking contacts in dimers of dithiatriazines. While ordinary single pancake bonds occur between radicals and already display significantly shorter interatomic distances in comparison to van der Waals (vdW) contacts, the double-bonded pancake dimer is based on diradicaloid or antiaromatic molecules and exhibits even shorter and stronger intermolecular bonds that breach into the range of extremely stretched single bonds in terms of bond distances and binding energies. These properties give rise to promising possibilities in the design of new materials with high electrical conductivity and for the field of spintronics. The analysis of the double pancake bond is based on cutting edge electron correlation theory combining multireference (nondynamical) effects and dispersion (dynamical) contributions in a balanced way providing accurate interaction energies and distributions of unpaired spins. It is also shown that the present examples do not stand isolated but that similar mechanisms operate in several analogous nonradical molecular systems to form double-bonded π-stacking pancake dimers. We report on the amazing properties of a new type of stacking interaction mechanism between π conjugated molecules in the form of a "double pancake bond" which breaks the record for short intermolecular distances and provides formidable strength for some π-π stacking interactions. PMID:25203200

  11. Transition metal-catalyzed process for addition of amines to carbon-carbon double bonds

    DOEpatents

    Hartwig, John F.; Kawatsura, Motoi; Loeber, Oliver

    2002-01-01

    The present invention is directed to a process for addition of amines to carbon-carbon double bonds in a substrate, comprising: reacting an amine with a compound containing at least one carbon-carbon double bond in the presence a transition metal catalyst under reaction conditions effective to form a product having a covalent bond between the amine and a carbon atom of the former carbon-carbon double bond. The transition metal catalyst comprises a Group 8 metal and a ligand containing one or more 2-electron donor atoms. The present invention is also directed to enantioselective reactions of amine compounds with compounds containing carbon-carbon double bonds, and a calorimetric assay to evaluate potential catalysts in these reactions.

  12. A model of phase transitions in double-well Morse potential: Application to hydrogen bond

    NASA Astrophysics Data System (ADS)

    Goryainov, S. V.

    2012-11-01

    A model of phase transitions in double-well Morse potential is developed. Application of this model to the hydrogen bond is based on ab initio electron density calculations, which proved that the predominant contribution to the hydrogen bond energy originates from the interaction of proton with the electron shells of hydrogen-bonded atoms. This model uses a double-well Morse potential for proton. Analytical expressions for the hydrogen bond energy and the frequency of O-H stretching vibrations were obtained. Experimental data on the dependence of O-H vibration frequency on the bond length were successfully fitted with model-predicted dependences in classical and quantum mechanics approaches. Unlike empirical exponential function often used previously for dependence of O-H vibration frequency on the hydrogen bond length (Libowitzky, Mon. Chem., 1999, vol.130, 1047), the dependence reported here is theoretically substantiated.

  13. Cavity partition and functionalization of a [2+3] organic molecular cage by inserting polar P[double bond, length as m-dash]O bonds.

    PubMed

    Feng, Genfeng; Liu, Wei; Peng, Yuxin; Zhao, Bo; Huang, Wei; Dai, Yafei

    2016-07-28

    The cavity of a [2+3] organic molecular cage was partitioned and functionalized by inserting inner-directed P[double bond, length as m-dash]O bonds, which shows CO2 capture and CH4 exclusion due to the size-matching and polarity effects. Computational results demonstrate that the successful segmentation via polar P[double bond, length as m-dash]O bonds facilitates the CO2 molecules to reside selectively inside the cavity. PMID:27356151

  14. Preparation of tert-butyl-capped polyenes containing up to 15 double bonds

    SciTech Connect

    Knoll, K.; Schrock, R.R. )

    1989-11-27

    7,8-Bis(trifluoromethyl)tricyclo(4.2.2.0{sup 2.5})deca-3,7,9-triene (TCDT) can be ring-opened in a controlled manner by W(CH-t-Bu)(NAr)(O-t-Bu){sub 2} (Ar = 2,6-C{sub 6}H{sub 3}-i-Pr{sub 2}) to give living oligomers from which the metal can be removed in a Wittig-like reaction with pivaldehyde or 4,4-dimethyl-trans-2-pentenal. Mixtures of odd and even polyenes have been analyzed by reversed-phase HPLC methods, and those having as many as 13 double bonds have been isolated by column chromatography on silica gel under dinitrogen at {minus}40{degree}C and characterized by {sup 1}H and {sup 13}C NMR and UV-vis studies. The 17-ene has been observed by HPLC. Polyenes containing more than 17 double bonds are relatively unstable under the reaction and subsequent isolation conditions; those containing between 11 and 15 double bonds decompose thermally progressively more readily. UV-vis and {sup 13}C and {sup 1}H NMR data have been collected and analyzed in detail for the trans(cis,trans){sub x} isomers for x = 1-5 (up to 11 double bonds) and for the odd and even all-trans forms containing up to nine double bonds.

  15. Kinetics and Mechanism of the Reaction of Ozone with Double Bonds

    NASA Astrophysics Data System (ADS)

    Razumovskii, S. D.; Zaikov, Gennadii E.

    1980-12-01

    Analysis of the results of recent studies has shown that the reaction of ozone with the double bonds of organic compounds apparently takes place not by a synchronous addition mechanism but through a reversible stage involving the formation of an intermediate complex of ozone with the double bond. The subsequent stages of the reaction involve the formation of a primary ozonide, its decomposition into two fragments, their combination, and a number of other transformations. The properties of the intermediate products, the relationship between the structure of the original alkenes and their reactivity towards ozone, the influence of the nature of the solvent on the direction and rate of the reaction, and the practical application of the reaction of ozone with double bonds in research and chemical technology have been examined. The bibliography contains 205 references.

  16. Linear, planar, and tubular molecular structures constructed by double planar tetracoordinate carbon D2hC2(BeH)4 species via hydrogen-bridged -BeH2Be- bonds.

    PubMed

    Zhao, Xue-Feng; Li, Haixia; Yuan, Cai-Xia; Li, Yan-Qin; Wu, Yan-Bo; Wang, Zhi-Xiang

    2016-01-15

    This computational study identifies the rhombic D2hC2 (BeH)4 (2a) to be a species featuring double planar tetracoordinate carbons (ptCs). Aromaticity and the peripheral BeBeBeBe bonding around CC core contribute to the stabilization of the ptC structure. Although the ptC structure is not a global minimum, its high kinetic stability and its distinct feature of having a bonded C2 core from having two separated carbon atoms in the global minimum and other low-lying minima could make the ptC structure to be preferred if the carbon source is dominated by C2 species. The electron deficiency of the BeH group allows the ptC species to serve as building blocks to construct large/nanostructures, such as linear chains, planar sheets, and tubes, via intermolecular hydrogen-bridged bonds (HBBs). Formation of one HBB bond releases more than 30.0 kcal/mol of energy, implying the highly exothermic formation processes and the possibility to synthesize these nano-size structures. PMID:26202851

  17. THP-1 macrophage lipid accumulation unaffected by fatty acid double bond geometric or positional configuration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dietary fatty acid type alters atherosclerotic lesion progression and macrophage lipid accumulation. Incompletely elucidated are the mechanisms by which fatty acids differing in double-bond geometric or positional configuration alter arterial lipid accumulation. The objective of this study was to ev...

  18. Directionality of Double-Bond Photoisomerization Dynamics Induced by a Single Stereogenic Center.

    PubMed

    Marchand, Gabriel; Eng, Julien; Schapiro, Igor; Valentini, Alessio; Frutos, Luis Manuel; Pieri, Elisa; Olivucci, Massimo; Léonard, Jérémie; Gindensperger, Etienne

    2015-02-19

    In light-driven single-molecule rotary motors, the photoisomerization of a double bond converts light energy into the rotation of a moiety (the rotor) with respect to another (the stator). However, at the level of a molecular population, an effective rotary motion can only be achieved if a large majority of the rotors rotate in the same, specific direction. Here we present a quantitative investigation of the directionality (clockwise vs counterclockwise) induced by a single stereogenic center placed in allylic position with respect to the reactive double bond of a model of the biomimetic indanylidene-pyrrolinium framework. By computing ensembles of nonadiabatic trajectories at 300 K, we predict that the photoisomerization is >70% unidirectional for the Z → E and E → Z conversions. Most importantly, we show that such directionality, resulting from the asymmetry of the excited state force field, can still be observed in the presence of a small (ca. 2°) pretwist or helicity of the reactive double bond. This questions the validity of the conjecture that a significant double-bond pretwist (e.g., >10°) in the ground state equilibrium structure of synthetic or natural rotary motors would be required for unidirectional motion. PMID:26262473

  19. Flow in out-of-plane double S-bonds

    NASA Technical Reports Server (NTRS)

    Schmidt, M. C.; Whitelaw, J. H.; Yianneskis, M.

    1986-01-01

    Developing flows in two out-of-plane double S-bend configurations have been measured by laser-Doppler anemometry. The first duct had a rectangular cross-section 40mmx40mm at the inlet and consisted of a uniform area 22.5 deg. - 22.5 deg. S-duct upstream with a 22.5 deg.- 22.5 deg. S- diffuser downstream. The second duct had a circular cross-section and consisted of a 45 deg. - 45 deg. uniform area S-duct upstream with a 22.5 deg. -22.5 deg. S-diffuser downstream. In both configurations the ratio of the mean radius of curvature to the inlet hydraulic diameter was 7.0, the exit-to-inlet area ratio of the diffusers was 1.5 and the ducts were connected so that the centerline of the S-duct lay in a plane normal to that of the S-diffuser. Streamwise and cross-stream velocity components were measured in laminar flow for the rectangular duct and in turbulent flow for both configurations; measurements of the turbulence levels, cross-correlations and wall static pressures were also made in the turbulent flow cases. Secondary flows of the first kind are present in the first S-duct and they are complemented or counteracted by the secondary flows generated by the area expansion and by the curvature of the S-diffusers downstream. Cross-stream velocities with magnitudes up to 0.19 and 0.11 of the bulk velocity were measured in the laminar and turbulent flows respectively in the rectangular duct and six cross-flow vortices were evident at the exit of the duct in both flow cases. The turbulent flow in the circular duct was qualitatively similar to that in the rectangular configuration, but the cross-stream velocities measured at the exit plane were smaller in the circular geometry. The results are presented in sufficient detail and accuracy for the assessment of numerical calculation methods and are listed in tabular form for this purpose.

  20. Dithienylthienothiophenebisimide, a Versatile Electron-Deficient Unit for Semiconducting Polymers.

    PubMed

    Saito, Masahiko; Osaka, Itaru; Suda, Yosuke; Yoshida, Hiroyuki; Takimiya, Kazuo

    2016-08-01

    A novel electron-deficient building unit, dithienylthienothiophenebisimide, and its polymers (PTBIs) are reported. Organic photovoltaic (OPV) cells based on PTBIs as p-type material exhibit 8.0% efficiencies with open-circuit voltages higher than 1 V. Interestingly, PTBIs also function as n-type material in OPVs depending on the molecular structure. These polymers also exhibit p-channel, n-channel, and ambipolar behaviors in field-effect transistors. PMID:27214577

  1. Determination of double bond position in conjugated dienes by chemical ionization mass spectrometry with isobutane

    SciTech Connect

    Doolittle, R.E.; Tumlinson, J.H.; Proveaux, A.

    1985-07-01

    The chemical ionization (CI) mass spectra of a series of functionalized conjugated dienes, including aldehydes, alcohols, formates, acetates, and hydrocarbons were investigated to determine whether fragmentations occur that are characteristic of the position of the conjugated system within the hydrocarbon chain. CI with isobutane as ionizing gas produces structure-specific fragment ions with m/z ratios that can be used to locate the positions of the double bonds in most of the cases studied. When the conjugated system is proximal to the functional group or conjugated with the functional group, other fragmentation processes take precedence. These patterns of fragmentations constitute a very useful analytical tool for the location of conjugated double bonds in a variety of natural products. 34 references, 3 tables, 3 figures.

  2. A diabatic state model for double proton transfer in hydrogen bonded complexes

    SciTech Connect

    McKenzie, Ross H.

    2014-09-14

    Four diabatic states are used to construct a simple model for double proton transfer in hydrogen bonded complexes. Key parameters in the model are the proton donor-acceptor separation R and the ratio, D{sub 1}/D{sub 2}, between the proton affinity of a donor with one and two protons. Depending on the values of these two parameters the model describes four qualitatively different ground state potential energy surfaces, having zero, one, two, or four saddle points. Only for the latter are there four stable tautomers. In the limit D{sub 2} = D{sub 1} the model reduces to two decoupled hydrogen bonds. As R decreases a transition can occur from a synchronous concerted to an asynchronous concerted to a sequential mechanism for double proton transfer.

  3. Double proton transfer behavior and one-electron oxidation effect in double H-bonded glycinamide-formic acid complex.

    PubMed

    Li, Ping; Bu, Yuxiang

    2004-11-22

    The behavior of double proton transfer occurring in a representative glycinamide-formic acid complex has been investigated at the B3LYP/6-311 + + G( * *) level of theory. Thermodynamic and, especially, kinetic parameters, such as tautomeric energy, equilibrium constant, and barrier heights have been discussed, respectively. The relevant quantities involved in the double proton transfer process, such as geometrical changes, interaction energies, and intrinsic reaction coordinate calculations have also been studied. Computational results show that the participation of a formic acid molecule favors the proceeding of the proton transfer for glycinamide compared with that without mediate-assisted case. The double proton transfer process proceeds with a concerted mechanism rather than a stepwise one since no ion-pair complexes have been located during the proton transfer process. The calculated barrier heights are 11.48 and 0.85 kcal/mol for the forward and reverse directions, respectively. However, both of them have been reduced by 2.95 and 2.61 kcal/mol to 8.53 and -1.76 kcal/mol if further inclusion of zero-point vibrational energy corrections, where the negative barrier height implies that the reverse reaction should proceed with barrierless spontaneously, analogous to that occurring between glycinamide and formamide. Furthermore, solvent effects on the thermodynamic and kinetic processes have also been predicted qualitatively employing the isodensity surface polarized continuum model within the framework of the self-consistent reaction field theory. Additionally, the oxidation process for the double H-bonded glycinamide-formic acid complex has also been investigated. Contrary to that neutral form possessing a pair of two parallel intermolecular H bonds, only a single H bond with a comparable strength has been found in its ionized form. The vertical and adiabatic ionization potentials for the neutral complex have been determined to be about 9.40 and 8.69 e

  4. Adhesive-bonded double-lap joints. [analytical solutions for static load carrying capacity

    NASA Technical Reports Server (NTRS)

    Hart-Smith, L. J.

    1973-01-01

    Explicit analytical solutions are derived for the static load carrying capacity of double-lap adhesive-bonded joints. The analyses extend the elastic solution Volkersen and cover adhesive plasticity, adherend stiffness imbalance and thermal mismatch between the adherends. Both elastic-plastic and bi-elastic adhesive representations lead to the explicit result that the influence of the adhesive on the maximum potential bond strength is defined uniquely by the strain energy in shear per unit area of bond. Failures induced by peel stresses at the ends of the joint are examined. This failure mode is particularly important for composite adherends. The explicit solutions are sufficiently simple to be used for design purposes

  5. Single-step in situ synthesis of double bond-grafted yttrium-hydroxide nanotube core-shell structures.

    PubMed

    Li, Weijia; Wang, Xun; Li, Yadong

    2004-01-21

    Novel MMA-Y(OH)(3) nanotube core-shell structures have been successfully prepared with double bonds successfully grafted on the surface through a single-step in-situ hydrothermal method. PMID:14737530

  6. Double-decker bis(tetradiazepinoporphyrazinato) rare earth complexes: crucial role of intramolecular hydrogen bonding.

    PubMed

    Tarakanova, Ekaterina N; Trashin, Stanislav A; Simakov, Anton O; Furuyama, Taniyuki; Dzuban, Alexander V; Inasaridze, Liana N; Tarakanov, Pavel A; Troshin, Pavel A; Pushkarev, Victor E; Kobayashi, Nagao; Tomilova, Larisa G

    2016-07-26

    A series of homoleptic bis{tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazinato}lanthanide sandwich complexes [(tBuPh)DzPz]2Ln (Ln = Lu, Er, Dy, Eu, Nd, Ce, La) were prepared and their physicochemical properties were studied to gain insight into the nature of specific interactions in diazepinoporphyrazines. The effect of annulated diazepine moieties and the Ln ionic radius on the properties of the complexes was investigated in comparison with double-decker phthalocyanines. A combination of experimental and theoretical studies revealed the presence of two types of hydrogen bonding interactions in the metal-free porphyrazine and the corresponding sandwich complexes, namely, interligand C-H(ax)N(meso) hydrogen bonding and O-HN(Dz) ligand-water interaction. The interligand hydrogen bonding imparts high stability of the ligand dimer and the double-decker compounds in a reduced state. This work is the first comprehensive investigation into the fundamental understanding of the unusual properties of diazepine-containing macroheterocycles. PMID:27396712

  7. Theoretical Analysis of the Effect of C═C Double Bonds on the Low-Temperature Reactivity of Alkenylperoxy Radicals.

    PubMed

    You, Xiaoqing; Chi, Yawei; He, Tanjin

    2016-08-01

    Biodiesel contains a large proportion of unsaturated fatty acid methyl esters. Its combustion characteristics, especially its ignition behavior at low temperatures, have been greatly affected by these C═C double bonds. In this work, we performed a theoretical analysis of the effect of C═C double bonds on the low-temperature reactivity of alkenylperoxy radicals, the key intermediates from the low-temperature combustion of biodiesel. To understand how double bonds affect the fate of peroxy radicals, we selected three representative peroxy radicals from heptane, heptene, and heptadiene having zero, one, and two double C═C bonds, respectively, for study. The potential energy surfaces were explored at the CBS-QB3 level, and the reaction rate constants were computed using canonical/variational transition state theories. We have found that the double bond is responsible for the very different bond dissociation energies of the various types of C-H bonds, which in turn affect significantly the reaction kinetics of alkenylperoxy radicals. PMID:27404895

  8. Recent Advances in Transition-Metal-Free Oxygenation of Alkene C=C Double Bonds for Carbonyl Generation.

    PubMed

    Wan, Jie-Ping; Gao, Yong; Wei, Li

    2016-08-01

    Carbonyl-forming reactions are a class of fundamental transformations in organic chemistry. Guided by the current importance of environmentally benign metal-free catalysis and synthesis, herein we review recent advances in carbonyl-generation reactions based on alkene C=C double oxygenation as well as related cascade reactions in the synthesis of diverse organic products. The content of this focus review consists of two important but different reaction models: oxygenation based on full C=C double-bond cleavage and oxygenation based on partial C=C double-bond cleavage. PMID:27237866

  9. On the bonding nature of electron states for the Fe-Mo double perovskite

    SciTech Connect

    Carvajal, E.; Cruz-Irisson, M.; Oviedo-Roa, R.; Navarro, O.

    2014-05-15

    The electronic transport as well as the effect of an external magnetic field has been investigated on manganese-based materials, spinels and perovskites. Potential applications of double perovskites go from magnetic sensors to electrodes in solid-oxide fuel cells; besides the practical interests, it is known that small changes in composition modify radically the physical properties of double perovskites. We have studied the Sr{sub 2}FeMoO{sub 6} double perovskite compound (SFMO) using first-principles density functional theory. The calculations were done within the generalized gradient approximation (GGA) scheme with the Perdew-Burke-Ernzerhof (PBE) functional. We have made a detailed analysis of each electronic state and the charge density maps around the Fermi level. For the electronic properties of SFMO it was used a primitive cell, for which we found the characteristic half-metallic behavior density of states composed by e{sub g} and t{sub 2g} electrons from Fe and Mo atoms. Those peaks were tagged as bonding or antibonding around the Fermi level at both, valence and conduction bands.

  10. A search for thermal isomerization of olefins to carbenes: Thermal generations of the silicon-nitrogen double bond

    SciTech Connect

    Zhang, Xianping.

    1990-09-21

    The first part of this thesis will search for the thermal isomerization of olefins to carbenes which is predicted to be a high energy process by calculations and has only been observed in a few strained olefins. The possibility of thermal isomerization of simple olefins to carbenes will be explored. Substitution of a silyl group on the double bond of an olefin allows a potential intermediate which has a {beta}-radical to the silyl group during the cis-trans isomerization. The effects of a trimethylsilyl group on this isomerization are the subject of this study. The second part of this thesis will include the generation and chemistry of intermediates containing a silicon-nitrogen double bond. The isomerization of parent silanimine to the aminosilylene was calculated to be a high energy process. New approaches to the silicon-nitrogen double bond will also be presented. 92 refs., 12 figs., 11 tabs.

  11. Flexible double betaines: molecular structures and hydrogen bonding in their crystalline hydrates

    NASA Astrophysics Data System (ADS)

    Wu, De-Dong; Mak, Thomas C. W.

    1994-09-01

    Crystalline hydrates of three flexible double betaines, -OOCCH 2N +Me 2-(CH 2) n-N +Me 2CH 2COO - ( 1n = 2; 2n = 3; 3n = 4) have been isolated and characterized by single-crystal X-ray analysis. 1·2H 2O crystallizes in the monoclinic space group C2/ c with Z = 4; 2·3H 2O and 3·2H 2O are both triclinic, space group Poverline1, with Z = 2 and 1, respectively. The site symmetries of 1, 2 and 3 are C2, C1 and Ci, respectively. The formation of hydrogen bonds generated by water molecules bridging neighboring carboxy oxygen atoms in different modes leads to polymeric zigzag chains in the dihydrates of 1 and 3, and a layer structure in the trihydrate of 2.

  12. Diffusion ordered spectroscopy for resolution of double bonded cis, trans-isomers

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin Rama; Suryaprakash, N.

    2012-06-01

    NMR spectroscopic separation of double bonded cis- and trans-isomers, that have different molecular shapes but identical mass have been carried out using Diffusion Ordered Spectroscopy (DOSY). The mixtures of fumaric acid and maleic acid, that have similar hydrodynamic radii, have resolved been 'on the basis of their diffusion coefficients arising due to their different tendencies to associate with micelles or reverse micelles. Sodium dodecyl sulfate (SDS) and Dioctyl sulfosuccinate sodium salt (AOT) have been used as the media to mimic the chromatographic conditions, modify the average mobility and to achieve differential diffusion rates. The best separation of the components has been achieved by Dioctyl sulfosuccinate sodium salt (AOT) in D2O solution.

  13. Ethenolysis: A Green Catalytic Tool to Cleave Carbon-Carbon Double Bonds.

    PubMed

    Bidange, Johan; Fischmeister, Cédric; Bruneau, Christian

    2016-08-22

    Remarkable innovations have been made in the field of olefin metathesis due to the design and preparation of new catalysts. Ethenolysis, which is cross-metathesis with ethylene, represents one catalytic transformation that has been used with the purpose of cleaving internal carbon-carbon double bonds. The objectives were either the ring opening of cyclic olefins to produce dienes or the shortening of unsaturated hydrocarbon chains to degrade polymers or generate valuable shorter terminal olefins in a controlled manner. This Review summarizes several aspects of this reaction: the catalysts, their degradation in the presence of ethylene, some parameters driving their productivity, the side reactions, and the applications of ethenolysis in organic synthesis and in potential industrial applications. PMID:27359344

  14. Theoretical study of the OH addition to the endocyclic and exocyclic double bonds of the d-limonene

    NASA Astrophysics Data System (ADS)

    Ramírez-Ramírez, Víctor M.; Nebot-Gil, Ignacio

    2005-06-01

    The initial step of the d-limonene + OH gas-phase reaction mechanism was investigated by means of ab initio calculations. We have considered eight different possibilities for the OH addition, corresponding to the two C-C double bonds, the two C atoms of each double bond, and the syn or anti orientation, with respect to the isopropenyl group (endocyclic attack) or the ring cycle (exocyclic attack). Activation energies calculated at the QCISD(T)/6-31G(d)//UMP2/6-31G(d) level, show that there are preferred orientations for the OH addition under atmospheric conditions of temperature and pressure.

  15. Bioactivation of clopidogrel and prasugrel: factors determining the stereochemistry of the thiol metabolite double bond.

    PubMed

    Dansette, Patrick M; Levent, Dan; Hessani, Assia; Mansuy, Daniel

    2015-06-15

    The antithrombotics of the tetrahydrothienopyridine series, clopidogrel and prasugrel, are prodrugs that must be metabolized in two steps to become pharmacologically active. The first step is the formation of a thiolactone metabolite. The second step is a further oxidation with the formation of a thiolactone sulfoxide whose hydrolytic opening leads to a sulfenic acid that is eventually reduced into the corresponding active cis thiol. Very few data were available on the formation of the isomer of the active cis thiol having a trans configuration of the double bond, the most striking result in that regard being that both cis and trans thiols were formed upon the metabolism of clopidogrel by human liver microsomes in the presence of glutathione (GSH), whereas only the cis thiol was detected in the sera of patients treated with this drug. This article shows that trans thiols are also formed upon the microsomal metabolism of prasugrel or its thiolactone metabolite in the presence of GSH and that metabolites having the trans configuration of the double bond are only formed when microsomal incubations are done in the presence of thiols, such as GSH, N-acetyl-cysteine, and mercaptoethanol. Intermediate formation of thioesters resulting from the reaction of GSH with the thiolactone sulfoxide metabolite appears to be responsible for trans thiol formation. Addition of human liver cytosol to the microsomal incubations led to a dramatic decrease of the formation of the trans thiol metabolites. These data suggest that cytosolic esterases would accelerate the hydrolytic opening of thiolactone sulfoxide intermediates and disfavor the formation of thioesters resulting from the reaction of these intermediates with GSH that is responsible for trans isomer formation. This would explain why trans thiols have not been detected in the sera of patients treated with clopidogrel. PMID:25970225

  16. Pancake π–π Bonding Goes Double: Unexpected 4e/All-Sites Bonding in Boron- and Nitrogen-Doped Phenalenyls

    SciTech Connect

    Tian, Yong-Hui; Sumpter, Bobby G.; Du, Shiyu; Huang, Jingsong

    2015-06-03

    Phenalenyl is an important neutral pi-radical due to its capability to form unconventional pancake pi-pi bonding interactions, whereas its analogues with graphitic boron (B) or nitrogen (N)-doping have been regarded as closed-shell systems and therefore received much less attention. By using high-level quantum chemistry calculations, we also show that the B- and N-doped closed-shell phenalenyls unexpectedly form open-shell singlet pi-dimers with diradicaloid character featuring 2e/all-sites double pi-pi bonding. Moreover, by proper substitutions, the doped phenalenyl derivatives can be made open-shell species that form closed shell singlet pi-dimers bound by stronger 4e/all-sites double pi-pi bonding. Moreover, covalent pi-pi bonding overlap is distributed on all of the atomic sites giving robust and genuine pancake-shaped pi-dimers which, depending on the number of electrons available in the bonding interactions, are equally or more stable than the pi-dimers of the pristine phenalenyl.

  17. Pancake π–π Bonding Goes Double: Unexpected 4e/All-Sites Bonding in Boron- and Nitrogen-Doped Phenalenyls

    DOE PAGESBeta

    Tian, Yong-Hui; Sumpter, Bobby G.; Du, Shiyu; Huang, Jingsong

    2015-06-03

    Phenalenyl is an important neutral pi-radical due to its capability to form unconventional pancake pi-pi bonding interactions, whereas its analogues with graphitic boron (B) or nitrogen (N)-doping have been regarded as closed-shell systems and therefore received much less attention. By using high-level quantum chemistry calculations, we also show that the B- and N-doped closed-shell phenalenyls unexpectedly form open-shell singlet pi-dimers with diradicaloid character featuring 2e/all-sites double pi-pi bonding. Moreover, by proper substitutions, the doped phenalenyl derivatives can be made open-shell species that form closed shell singlet pi-dimers bound by stronger 4e/all-sites double pi-pi bonding. Moreover, covalent pi-pi bonding overlap ismore » distributed on all of the atomic sites giving robust and genuine pancake-shaped pi-dimers which, depending on the number of electrons available in the bonding interactions, are equally or more stable than the pi-dimers of the pristine phenalenyl.« less

  18. Accurate characterization of wafer bond toughness with the double cantilever specimen

    NASA Astrophysics Data System (ADS)

    Turner, Kevin T.; Spearing, S. Mark

    2008-01-01

    The displacement loaded double cantilever test, also referred to as the "Maszara test" and the "crack opening method" by the wafer bonding community, is a common technique used to evaluate the interface toughness or surface energy of direct wafer bonds. While the specimen is widely used, there has been a persistent question as to the accuracy of the method since the actual specimen geometry differs from the ideal beam geometry assumed in the expression used for data reduction. The effect of conducting the test on whole wafer pairs, in which the arms of cantilevers are wide plates rather than slender beams, is examined in this work using finite element analysis. A model is developed to predict the equilibrium shape of the crack front and to develop a corrected expression for calculating interface toughness from crack length measurements obtained in tests conducted on whole wafer pairs. The finite element model, which is validated through comparison to experiments, demonstrates that using the traditional beam theory-based expressions for data reduction can lead to errors of up to 25%.

  19. Three-Component Azidation of Styrene-Type Double Bonds: Light-Switchable Behavior of a Copper Photoredox Catalyst**

    PubMed Central

    Fumagalli, Gabriele; Rabet, Pauline T G; Boyd, Scott; Greaney, Michael F

    2015-01-01

    [Cu(dap)2]Cl effectively catalyzes azide addition from the Zhdankin reagent to styrene-type double bonds, and subsequent addition of a third component to the benzylic position. In the presence of light, a photoredox cycle is implicated with polar components such as methanol or bromide adding to a benzylic cation. In the absence of light, by contrast, double azidation takes place to give diazides. Therefore, regioselective double functionalization can be achieved in good to excellent yields, with a switch between light and dark controlling the degree of azidation. PMID:26119004

  20. Bent Bonds and Multiple Bonds.

    ERIC Educational Resources Information Center

    Robinson, Edward A.; Gillespie, Ronald J.

    1980-01-01

    Considers carbon-carbon multiple bonds in terms of Pauling's bent bond model, which allows direct calculation of double and triple bonds from the length of a CC single bond. Lengths of these multiple bonds are estimated from direct measurements on "bent-bond" models constructed of plastic tubing and standard kits. (CS)

  1. Reduction of N-allylamides by LiAlH4: unexpected attack of the double bond with mechanistic studies of product and byproduct formation.

    PubMed

    Thiedemann, Birk; Schmitz, Christin M L; Staubitz, Anne

    2014-11-01

    The reduction of secondary allyl amides with LiAlH4 can lead to a concomitant reduction of the double bond. Previously, an excess of LiAlH4 in hazardous solvents was used for the reduction. This work discusses optimized reaction conditions in tBuOMe as a safe solvent, with only a 1.5-fold excess of LiAlH4, without reduction of the double bond in most cases. (1)H and (2)D NMR spectroscopic studies give evidence for the mechanism of the reduction of the amide as well as the double bond: Amide reduction generally precedes double bond reduction. Sterically hindered allylamides are an exception. They are reduced considerably more slowly at higher temperatures, and double bond reduction is observed before amide reduction has gone to completion. PMID:25347383

  2. A fluorescent sensor for Zn(2+) and NO2(-) based on the rational control of C[double bond, length as m-dash]N isomerization.

    PubMed

    Liu, Zheng; Peng, Cuina; Wang, Ying; Pei, Meishan; Zhang, Guangyou

    2016-05-01

    A new strategy for the ultrasensitive sensing of cations and anions based on the control of C[double bond, length as m-dash]N isomerization has been developed. Imine-derived ligand is non-fluorescent due to the C[double bond, length as m-dash]N isomerization process, whereas its ternary complex with ZnCl2 is moderately fluorescent because of the partial inhibition of C[double bond, length as m-dash]N isomerization. Such a ternary complex can give a remarkable fluorescence increase when it interacts with nitrite because of the much more efficient suppression of C[double bond, length as m-dash]N isomerization. This modulation process of C[double bond, length as m-dash]N isomerization can thus be used for the highly selective detection of Zn(2+) and NO2(-) in an aqueous solution. PMID:27075971

  3. Novel dehydrogenase catalyzes oxidative hydrolysis of carbon-nitrogen double bonds for hydrazone degradation.

    PubMed

    Itoh, Hideomi; Suzuta, Tetsuya; Hoshino, Takayuki; Takaya, Naoki

    2008-02-29

    Hydrazines and their derivatives are versatile artificial and natural compounds that are metabolized by elusive biological systems. Here we identified microorganisms that assimilate hydrazones and isolated the yeast, Candida palmioleophila MK883. When cultured with adipic acid bis(ethylidene hydrazide) as the sole source of carbon, C. palmioleophila MK883 degraded hydrazones and accumulated adipic acid dihydrazide. Cytosolic NAD+- or NADP+-dependent hydrazone dehydrogenase (Hdh) activity was detectable under these conditions. The production of Hdh was inducible by adipic acid bis(ethylidene hydrazide) and the hydrazone, varelic acid ethylidene hydrazide, under the control of carbon catabolite repression. Purified Hdh oxidized and hydrated the C=N double bond of acetaldehyde hydrazones by reducing NAD+ or NADP+ to produce relevant hydrazides and acetate, the latter of which the yeast assimilated. The deduced amino acid sequence revealed that Hdh belongs to the aldehyde dehydrogenase (Aldh) superfamily. Kinetic and mutagenesis studies showed that Hdh formed a ternary complex with the substrates and that conserved Cys is essential for the activity. The mechanism of Hdh is similar to that of Aldh, except that it catalyzed oxidative hydrolysis of hydrazones that requires adding a water molecule to the reaction catalyzed by conventional Aldh. Surprisingly, both Hdh and Aldh from baker's yeast (Ald4p) catalyzed the Hdh reaction as well as aldehyde oxidation. Our findings are unique in that we discovered a biological mechanism for hydrazone utilization and a novel function of proteins in the Aldh family that act on C=N compounds. PMID:18096698

  4. A Bonded Double-Doped Graphene Nanoribbon Framework for Advanced Electrocatalysis.

    PubMed

    Chen, Liang; Xiao, Jingjing; Liu, Baohong; Yi, Tao

    2016-07-01

    The preparation of a low-cost, high-efficient, and stable electrocatalyst as an alternative to platinum for the oxygen reduction reaction (ORR) is especially important to various energy storage components, such as fuel cells and metal-air batteries. Here, we report a new type of bonded double-doped graphene nanoribbon-based nonprecious metal catalysts in which Fe3C nanoparticles embedded in Fe-N-doped graphene nanoribbon (GNRs) frameworks through a simple pyrolysis. The as-obtained catalyst possesses several desirable merits for the ORR, such as diverse high-efficiency catalytic sites, a high specific surface area, an ideal hierarchical cellular structure, and a highly conductive N-doped GNR network. Accordingly, the prepared catalyst shows a superior ORR activity (an onset potential of 0.02 V and a half-wave potential of -0.148 V versus an Ag/AgCl electrode) in alkaline media, close to the commercial Pt/C catalyst. Moreover, it also displays good ORR behavior in an acidic solution. PMID:27300690

  5. Double Pancake Versus Long Chalcogen-Chalcogen Bonds in Six-Membered C,N,S-Heterocycles.

    PubMed

    Haberhauer, Gebhard; Gleiter, Rolf

    2016-06-13

    The double "pancake" bonding in the dimers of the six-membered heterocycles 1,3-dithia-2,4,6-triazine (4) and 1,3-dithia-2,4-diazine (16) were investigated by means of high-level quantum chemical calculations (B3LYP and CCSD(T)). It was found that the S-S dimers, 20 a and 27, are not the most stable isomers, but the dimers showing short S-N (21 a) and S-C (25, 28) bonds. An investigation of the 5-phenyl-1,3-dithia-2,4,6-triazine (4 b) yields that the syn dimer with two S-S bonds (2.57 Å) is the most stable one. In this dimer, the phenyl groups are placed on top of each other. The additional dispersion energy of the phenyl rings causes a stabilization of the syn-S-S (C2v -like) isomer. As a result, two weak albeit relevant single S-S bonds (2.57 Å) are predicted. These findings contradict the recently published concept of double "pancake" bonding in the dimer 4 b2 . PMID:27172139

  6. Competitive Low Pressure Oxygen Plasma Interactions with Different= Carbon-Carbon Double Bonds

    NASA Astrophysics Data System (ADS)

    Patiño, P.; Sifontes, A.; Gambús, G.

    1999-10-01

    Recently we have shown advances from reactions of O(^3P) with both, l ong-chain hydrocarbons and refinery residuum. The oxidation products of t he process, a mixture of alcohols, epoxides and carbonyl compounds, might have potential properties as additives in formulating fuels. This work s hows the results of the interactions of an oxygen plasma with double bond s, both olefin and aromatic, in the same compound. The reactions have bee n carried out by making the plasma, created by a high voltage glow discha rge, reach the low vapor pressure surface of liquid 4-phenyl-1-butene. Th is (3 mL) was cooled down to -45 ^oC in a glass reactor, applied power was 24 W, at an oxygen pressure of 20 Pa. Products were analyzed by IR, N MR and mass spectroscopies. Conversions were studied as a function of the reaction time, this ranging from 5 to 120 minutes. At short times the O( ^3P) atoms produced in the discharge only reacted with the alkene fra ction of the hydrocarbon, 4-phenyl-1,2-epoxibutane (52%) and 4-phenyl-bu tanal (48%) being the products. Reactions on the benzene ring were obser ved from about 30 minutes on, the corresponding phenols having being prod uced at ratios ortho:para:meta :: 4:1:0.7. At 120 minutes, the ol efin have been completely oxidized and a low fraction of the non-equivale nt two methylene groups have reacted to produce alcohols and ketones.

  7. Rhodium- and iridium-catalyzed dehydrogenative cyclization through double C-H bond cleavages to produce fluorene derivatives.

    PubMed

    Itoh, Masaki; Hirano, Koji; Satoh, Tetsuya; Shibata, Yu; Tanaka, Ken; Miura, Masahiro

    2013-02-15

    The rhodium-catalyzed cyclization of a series of 2,2-diarylalkanoic acids in the presence of copper acetate as an oxidant smoothly proceeded through double C-H bond cleavages and subsequent decarboxylation to produce the corresponding fluorene derivatives. The direct cyclization of triarylmethanols also took place efficiently by using an iridium catalyst in place of the rhodium, while the hydroxy function was still intact. PMID:23360206

  8. Rhodium-catalyzed annulative coupling of 3-phenylthiophenes with alkynes involving double C-H bond cleavages.

    PubMed

    Iitsuka, Tomonori; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

    2014-01-01

    Double CH bond activation took place efficiently upon treatment of 3-phenylthiophenes with alkynes in the presence of a rhodium catalyst and a copper salt oxidant to form the corresponding naphthothiophene derivatives. Dehydrogenative coupling with alkenes was also found to occur on the phenyl moiety rather than the thiophene ring. These reactions provide straightforward synthetic methods for π-conjugated molecules involving a thiophene unit from readily available, simple building blocks. PMID:24288235

  9. Functionalization of the benzobicyclo[3.2.1] octadiene skeleton possessing one isolated double bond via photocatalytic oxygenation

    NASA Astrophysics Data System (ADS)

    Vuk, Dragana; Horváth, Ottó; Marinić, Željko; Škorić, Irena

    2016-03-01

    Photocatalytic oxygenation of three phenyl derivatives of a bicyclic skeleton with a free double bond 1a, 1b and 1c were carried out by utilizing a cationic and an anionic manganese(III) porphyrin irradiated in the visible range. While photocatalysis of 1a and 1b led to the formation of the corresponding hydroperoxy derivatives 2 and 3, respectively, (besides unidentified high-molecular-weight products) in the presence of the anionic Mn(III) porphyrin, the cationic photocatalyst proved to be less efficient and less selective with 1a. In the case of 1b, also with the cationic porphyrin, the corresponding hydroperoxy derivative (3) was the main product at a shorter reaction time (2 h), whereas a longer irradiation (4 h) led to the significant formation of a keto derivative (5) with a hydroperoxy substituent and a free double bond at positions deviating from those in the previous products (2 and 3). A dramatic change in the reactivity was observed for the methoxy derivative (1c). It gave only traces of identifiable products by using the anionic photocatalyst, while application of the cationic Mn(III) porphyrin resulted in a relatively efficient formation of an epoxy derivative (6) due to the reaction of the isolated double bond.

  10. Fracture Analysis of Double-Side Adhesively Bonded Composite Repairs to Cracked Aluminium Plate Using Line Spring Model

    NASA Astrophysics Data System (ADS)

    Niu, Yong; Su, Weiguo

    2016-06-01

    A line spring model is developed for analyzing the fracture problem of cracked metallic plate repaired with the double-sided adhesively bonded composite patch. The restraining action of the bonded patch is modeled as continuous distributed linear springs bridging the crack faces provided that the cracked plate is subjected to extensional load. The effective spring constant is determined from 1-D bonded joint theory. The hyper-singular integral equation (HSIE), which can be solved using the second kind Chebyshev polynomial expansion method, is applied to determine the crack opening displacements (COD) and the crack tip stress intensity factors (SIF) of the repaired cracked plate. The numerical result of SIF for the crack-tip correlates very well with the finite element (FE) computations based on the virtual crack closure technique (VCCT). The present analysis approaches and mathematical techniques are critical to the successful design, analysis and implementation of crack patching.

  11. Double-bridge bonding of aluminium and hydrogen in the crystal structure of gamma-AlH3.

    PubMed

    Yartys, Volodymyr A; Denys, Roman V; Maehlen, Jan Petter; Frommen, Christoph; Fichtner, Maximilian; Bulychev, Boris M; Emerich, Hermann

    2007-02-19

    Aluminum trihydride (alane) is one of the most promising among the prospective solid hydrogen-storage materials, with a high gravimetric and volumetric density of hydrogen. In the present work, the alane, crystallizing in the gamma-AlH3 polymorphic modification, was synthesized and then structurally characterized by means of synchrotron X-ray powder diffraction. This study revealed that gamma-AlH3 crystallizes with an orthorhombic unit cell (space group Pnnm, a = 5.3806(1) A, b = 7.3555(2) A, c = 5.77509(5) A). The crystal structure of gamma-AlH3 contains two types of AlH6 octahedra as the building blocks. The Al-H bond distances in the structure vary in the range of 1.66-1.79 A. A prominent feature of the crystal structure is the formation of the bifurcated double-bridge bonds, Al-2H-Al, in addition to the normal bridge bonds, Al-H-Al. This former feature has not been previously reported for Al-containing hydrides so far. The geometry of the double-bridge bond shows formation of short Al-Al (2.606 A) and Al-H (1.68-1.70 A) bonds compared to the Al-Al distances in Al metal (2.86 A) and Al-H distances for Al atoms involved in the formation of normal bridge bonds (1.769-1.784 A). The crystal structure of gamma-AlH3 contains large cavities between the AlH6 octahedra. As a consequence, the density is 11% less than for alpha-AlH3. PMID:17291106

  12. Localization of double bonds in triacylglycerols using high-performance liquid chromatography/atmospheric pressure chemical ionization ion-trap mass spectrometry.

    PubMed

    Háková, Eva; Vrkoslav, Vladimír; Míková, Radka; Schwarzová-Pecková, Karolina; Bosáková, Zuzana; Cvačka, Josef

    2015-07-01

    A method for localizing double bonds in triacylglycerols using high-performance liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization (APCI) was developed. The technique was based on collision-induced dissociation or pulsed Q collision-induced dissociation of the C3H5N(+•) adducts ([M + 55](+•)) formed in the presence of acetonitrile in the APCI source. The spectra were investigated using a large series of standards obtained from commercial sources and prepared by randomization. The fragmentation spectra made it possible to determine (i) the total number of carbons and double bonds in the molecule, (ii) the number of carbons and double bonds in acyls, (iii) the acyl in the sn-2 position on the glycerol backbone, and (iv) the double-bond positions in acyls. The double-bond positions were determined based on two types of fragments (alpha and omega ions) formed by cleavages of C-C bonds vinylic to the original double bond. The composition of the acyls and their positions on glycerol were established from the masses and intensities of the ions formed by the elimination of fatty acids from the [M + 55](+•) precursor. The method was applied for the analysis of triacylglycerols in olive oil and vernix caseosa. PMID:25701424

  13. Effect of the Hydrogen Bond in Photoinduced Water Dissociation: A Double-Edged Sword.

    PubMed

    Yang, Wenshao; Wei, Dong; Jin, Xianchi; Xu, Chenbiao; Geng, Zhenhua; Guo, Qing; Ma, Zhibo; Dai, Dongxu; Fan, Hongjun; Yang, Xueming

    2016-02-18

    Photoinduced water dissociation on rutile-TiO2 was investigated using various methods. Experimental results reveal that the water dissociation occurs via transferring an H atom to a bridge bonded oxygen site and ejecting an OH radical to the gas phase during irradiation. The reaction is strongly suppressed as the water coverage increases. Further scanning tunneling microscopy study demonstrates that hydrogen bonds between water molecules have a dramatic effect on the reaction. Interestingly, a single hydrogen bond in water dimer enhances the water dissociation reaction, while one-dimensional hydrogen bonds in water chains inhibit the reaction. Density functional theory calculations indicate that the effect of hydrogen bonds on the OH dissociation energy is likely the origin of this remarkable behavior. The results suggest that avoiding a strong hydrogen bond network between water molecules is crucial for water splitting. PMID:26810945

  14. Reliable vibrational wavenumbers for C[double bond, length as m-dash]O and N-H stretchings of isolated and hydrogen-bonded nucleic acid bases.

    PubMed

    Fornaro, Teresa; Biczysko, Malgorzata; Bloino, Julien; Barone, Vincenzo

    2016-03-16

    The accurate prediction of vibrational wavenumbers for functional groups involved in hydrogen-bonded bridges remains an important challenge for computational spectroscopy. For the specific case of the C[double bond, length as m-dash]O and N-H stretching modes of nucleobases and their oligomers, the paucity of experimental reference values needs to be compensated by reliable computational data, which require the use of approaches going beyond the standard harmonic oscillator model. Test computations performed for model systems (formamide, acetamide and their cyclic homodimers) in the framework of the second order vibrational perturbation theory (VPT2) confirmed that anharmonic corrections can be safely computed by global hybrid (GHF) or double hybrid (DHF) functionals, whereas the harmonic part is particularly challenging. As a matter of fact, GHFs perform quite poorly and even DHFs, while fully satisfactory for C[double bond, length as m-dash]O stretchings, face unexpected difficulties when dealing with N-H stretchings. On these grounds, a linear regression for N-H stretchings has been obtained and validated for the heterodimers formed by 4-aminopyrimidine with 6-methyl-4-pyrimidinone (4APM-M4PMN) and by uracil with water. In view of the good performance of this computational model, we have built a training set of B2PLYP-D3/maug-cc-pVTZ harmonic wavenumbers (including linear regression scaling for N-H) for six-different uracil dimers and a validation set including 4APM-M4PMN, one of the most stable hydrogen-bonded adenine homodimers, as well as the adenine-uracil, adenine-thymine, guanine-cytosine and adenine-4-thiouracil heterodimers. Because of the unfavourable scaling of DHF harmonic wavenumbers with the dimensions of the investigated systems, we have optimized a linear regression of B3LYP-D3/N07D harmonic wavenumbers for the training set, which has been next checked against the validation set. This relatively cheap model, which shows very good agreement with

  15. Carbon-nitrogen bond construction and carbon-oxygen double bond cleavage on a molecular titanium oxonitride: a combined experimental and computational study.

    PubMed

    Carbó, Jorge J; García-López, Diego; González-Del Moral, Octavio; Martín, Avelino; Mena, Miguel; Santamaría, Cristina

    2015-10-01

    New carbon-nitrogen bonds were formed on addition of isocyanide and ketone reagents to the oxonitride species [{Ti(η(5)-C5Me5)(μ-O)}3(μ3-N)] (1). Reaction of 1 with XylNC (Xyl = 2,6-Me2C6H3) in a 1:3 molar ratio at room temperature leads to compound [{Ti(η(5)-C5Me5)(μ-O)}3(μ-XylNCCNXyl)(NCNXyl)] (2), after the addition of the nitrido group to one coordinated isocyanide and the carbon-carbon coupling of the other two isocyanide molecules have taken place. Thermolysis of 2 gives [{Ti(η(5)-C5Me5)(μ-O)}3(XylNCNXyl)(CN)] (3) where the heterocumulene [XylNCCNXyl] moiety and the carbodiimido [NCNXyl] fragment in 2 have undergone net transformations. Similarly, tert-butyl isocyanide (tBuNC) reacts with the starting material 1 under mild conditions to give the paramagnetic derivative [{Ti3(η(5)-C5Me5)3(μ-O)3(NCNtBu)}2(μ-CN)2] (4). However, compound 1 provides the oxo ketimide derivatives [{Ti3(η(5)-C5Me5)3(μ-O)4}(NCRPh)] [R = Ph (5), p-Me(C6H4) (6), o-Me(C6H4) (7)] upon reaction with benzophenone, p-methylbenzophenone, and o-methylbenzophenone, respectively. In these reactions, the carbon-oxygen double bond is completely ruptured, leading to the formation of a carbon-nitrogen and two metal-oxygen bonds. The molecular structures of complexes 2-4, 6, and 7 were determined by single-crystal X-ray diffraction analyses. Density functional theory calculations were performed on the incorporation of isocyanides and ketones to the model complex [{Ti(η(5)-C5H5)(μ-O)}3(μ3-N)] (1H). The mechanism involves the coordination of the substrates to one of the titanium metal centers, followed by an isomerization to place those substrates cis with respect to the apical nitrogen of 1H, where carbon-nitrogen bond formation occurs with a low-energy barrier. In the case of aryl isocyanides, the resulting complex incorporates additional isocyanide molecules leading to a carbon-carbon coupling. With ketones, the high oxophilicity of titanium promotes the unusual total cleavage of the

  16. Extraordinary stability of naphthalenediimide radical ion and its ultra-electron-deficient precursor: strategic role of the phosphonium group.

    PubMed

    Kumar, Sharvan; Ajayakumar, M R; Hundal, Geeta; Mukhopadhyay, Pritam

    2014-08-27

    Stabilization of radical ions and highly electron-deficient systems under ambient conditions is of great significance. A new design concept is presented that applies the multifaceted features of the phosphonium group to achieve isolation of (a) the first naphthalenediimide (NDI) radical ion [(1a•+)BPh4(–)] as single crystals and (b) an ultra-electron-deficient NDI [(1a(2+))2BF4(–)] having the lowest LUMO level recorded for an NDI, overwhelming the formative tetracyanoquinodimethane (TCNQ) molecule. Both 1a•+ and 1a(2+) exhibit unprecedented stability to normal workup procedures, chromatography, and anion metathesis in open air. To our knowledge, this is the first instance where radical ions stable toward chromatography have been obtained, which is a noteworthy development in the field of synthetic radical chemistry. The crucial components of thermodynamic and kinetic stabilization, namely, the nonbonded P···O interaction, hypervalency, and propeller-like shape of the phosphonium groups in 1a(2+) and 1a•+, were substantiated by crystallography and theoretical studies. Natural bond orbital (NBO) calculations validated the P···O contact to be an nO → σP–C* orbital interaction. Spontaneous electron transfer reactions of 1a(2+) even in nonpolar solvents, anion−π interactions of 1a(2+) with the naphthalene core, and panchromism of 1a•+ are the other emergent properties. The high-yielding (∼90%) in situ synthesis of 1a•+ and the extraordinary stability fostered by the phosphonium group have the potential to turn hitherto unstable organic systems into a new genre of stable off-the-shelf systems. PMID:25093533

  17. Endohedral fullerene with μ3-carbido ligand and titanium-carbon double bond stabilized inside a carbon cage.

    PubMed

    Svitova, A L; Ghiassi, K B; Schlesier, C; Junghans, K; Zhang, Y; Olmstead, M M; Balch, A L; Dunsch, L; Popov, A A

    2014-01-01

    In all metallofullerenes known before this work, metal atoms form single highly polar bonds with non-metal atoms in endohedral cluster. This is rather surprising for titanium taking into account the diversity of organotitanium compounds. Here we show that the arc-discharge synthesis of mixed titanium-lutetium metallofullerenes in the presence of ammonia, melamine or methane unexpectedly results in the formation of TiLu2C@I(h)-C80 with an icosahedral Ih(7) carbon cage. Single-crystal X-ray diffraction and spectroscopic studies of the compound reveal an unprecedented endohedral cluster with a μ3-carbido ligand and Ti-C double bond. The Ti(IV) in TiLu2C@I(h)-C80 can be reversibly reduced to the Ti(III) state. The Ti = C bonding and Ti-localized lowest unoccupied molecular orbital in TiLu2C@Ih-C80 bear a certain resemblance to titanium alkylidenes. TiLu2C@I(h)-C80 is the first metallofullerene with a multiple bond between a metal and the central, non-metal atom of the endohedral cluster. PMID:24699547

  18. A double bond-conjugated dimethylnitrobenzene-type photolabile nitric oxide donor with improved two-photon cross section.

    PubMed

    Ieda, Naoya; Hishikawa, Kazuhiro; Eto, Kei; Kitamura, Kai; Kawaguchi, Mitsuyasu; Suzuki, Takayoshi; Fukuhara, Kiyoshi; Miyata, Naoki; Furuta, Toshiaki; Nabekura, Junichi; Nakagawa, Hidehiko

    2015-08-15

    Photocontrollable NO donors enable precise spatiotemporal release of NO under physiological conditions. We designed and synthesized a novel dimethylnitrobenzene-type NO donor, Flu-DNB-DB, which contains a carbon-carbon double bond in place of the amide bond of previously reported Flu-DNB. Flu-DNB-DB releases NO in response to one-photon activation in the blue wavelength region, and shows a greatly increased two-photon cross-section (δu) at 720 nm (Flu-DNB: 0.12 GM, Flu-DNB-DB: 0.98 GM). We show that Flu-DNB-DB enables precisely controlled intracellular release of NO in response to 950 nm pulse laser irradiation for as little as 1s. This near-infrared-light-controllable NO source should be a valuable tool for studies on the biological roles of NO. PMID:26073004

  19. Characterization of Wax Esters by Electrospray Ionization Tandem Mass Spectrometry: Double Bond Effect and Unusual Product Ions

    PubMed Central

    Chen, Jianzhong; Green, Kari B; Nichols, Kelly K

    2015-01-01

    A series of different types of wax esters (represented by RCOOR′) were systematically studied by using electrospray ionization (ESI) collision-induced dissociation tandem mass spectrometry (MS/MS) along with pseudo MS3 (in-source dissociation combined with MS/MS) on a quadrupole time-of-flight (Q-TOF) mass spectrometer. The tandem mass spectra patterns resulting from dissociation of ammonium/proton adducts of these wax esters were influenced by the wax ester type and the collision energy applied. The product ions [RCOOH2]+, [RCO]+ and [RCO – H2O]+ that have been reported previously were detected; however, different primary product ions were demonstrated for the three wax ester types including: 1) [RCOOH2]+ for saturated wax esters, 2) [RCOOH2]+, [RCO]+ and [RCO – H2O]+ for unsaturated wax esters containing only one double bond in the fatty acid moiety or with one additional double bond in the fatty alcohol moiety, and 3) [RCOOH2]+ and [RCO]+ for unsaturated wax esters containing a double bond in the fatty alcohol moiety alone. Other fragments included [R′]+ and several series of product ions for all types of wax esters. Interestingly, unusual product ions were detected, such as neutral molecule (including water, methanol and ammonia) adducts of [RCOOH2]+ ions for all types of wax esters and [R′ – 2H]+ ions for unsaturated fatty acyl-containing wax esters. The patterns of tandem mass spectra for different types of wax esters will inform future identification and quantification approaches of wax esters in biological samples as supported by a preliminary study of quantification of isomeric wax esters in human meibomian gland secretions. PMID:26178197

  20. Low-lying singlet states of carotenoids having 8-13 conjugated double bonds as determined by electronic absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Nakamura, Ryosuke; Kanematsu, Yasuo; Koyama, Yasushi; Nagae, Hiroyoshi; Nishio, Tomohiro; Hashimoto, Hideki; Zhang, Jian-Ping

    2005-07-01

    Electronic absorption spectra were recorded at room temperature in solutions of carotenoids having different numbers of conjugated double bonds, n = 8-13, including a spheroidene derivatives, neurosporene, spheroidene, lycopene, anhydrorhodovibrin and spirilloxanthin. The vibronic states of 1Bu+(v=0-4), 2Ag-(v=0-3), 3Ag- (0) and 1Bu- (0) were clearly identified. The arrangement of the four electronic states determined by electronic absorption spectroscopy was identical to that determined by measurement of resonance Raman excitation profiles [K. Furuichi et al., Chem. Phys. Lett. 356 (2002) 547] for carotenoids in crystals.

  1. Quantum dynamics study of fulvene double bond photoisomerization: The role of intramolecular vibrational energy redistribution and excitation energy

    SciTech Connect

    Blancafort, Lluis; Gatti, Fabien; Meyer, Hans-Dieter

    2011-10-07

    The double bond photoisomerization of fulvene has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method. Fulvene is a test case to develop optical control strategies based on the knowledge of the excited state decay mechanism. The decay takes place on a time scale of several hundred femtoseconds, and the potential energy surface is centered around a conical intersection seam between the ground and excited state. The competition between unreactive decay and photoisomerization depends on the region of the seam accessed during the decay. The dynamics are carried out on a four-dimensional model surface, parametrized from complete active space self-consistent field calculations, that captures the main features of the seam (energy and locus of the seam and associated branching space vectors). Wave packet propagations initiated by single laser pulses of 5-25 fs duration and 1.85-4 eV excitation energy show the principal characteristics of the first 150 fs of the photodynamics. Initially, the excitation energy is transferred to a bond stretching mode that leads the wave packet to the seam, inducing the regeneration of the reactant. The photoisomerization starts after the vibrational energy has flowed from the bond stretching to the torsional mode. In our propagations, intramolecular energy redistribution (IVR) is accelerated for higher excess energies along the bond stretch mode. Thus, the competition between unreactive decay and isomerization depends on the rate of IVR between the bond stretch and torsion coordinates, which in turn depends on the excitation energy. These results set the ground for the development of future optical control strategies.

  2. An ab initio study of relationships between bond lengths and the harmonic and anharmonic cross-coupling constants involving the double bonds in hetero-atom substituted conjugated dienes

    NASA Astrophysics Data System (ADS)

    Bock, Charles W.; Trachtman, Mendel; George, Philip

    1982-12-01

    The lengths of the terminal double bonds and the central CC single bond, and the cross-coupling constant involving the double bonds, calculated ab initio using the unscaled 4-31G basis set, are reported for 15 planar conformers of conjugated dienes containing the OCC'C″ grouping, 9 planar conformers containing the OCC'N grouping, and 6 planar conformers containing the OCC'O'grouping. The larger values for the CC bond length tend to be associated with the smaller values for the double-bond lengths, and vice versa. A linear relationship holds fairly well between rcc and the sum of the double-bond lengths. The sign of the cross-coupling constant is the same for each type of conjugated diene, negative for foc.c'c″ and foc.c'N' but positive for foc.c'o'. The values of foc.c'c″ and f oc.c'N are larger the smaller rcc' in accord with a linear relationship. For all three types of diene the values for pairs of cis and trans conformers do not differ very much, the ratio fcis/ ftrans being a little greater than 1 in ten cases and a little less than 1 in six cases. This lack of any marked difference between cis and trans conformers suggests that the coupling between the double bonds occurs in the main via the bonded framework of the molecule, and that "through-space" interactions, which would be a special feature of cis conformers, are of relatively little importance.

  3. Role of the protein cavity in phytochrome chromoprotein assembly and double-bond isomerization: a comparison with model compounds.

    PubMed

    Rohmer, Thierry; Lang, Christina; Gärtner, Wolfgang; Hughes, Jon; Matysik, Jörg

    2010-01-01

    Difference patterns of (13)C NMR chemicals shifts for the protonation of a free model compound in organic solution, as reported in the literature (M. Stanek, K. Grubmayr [1998] Chem. Eur. J.4, 1653-1659), were compared with changes in the protonation state occurring during holophytochrome assembly from phycocyanobilin (PCB) and the apoprotein. Both processes induce identical changes in the NMR signals, indicating that the assembly process is linked to protonation of the chromophore, yielding a cationic cofactor in a heterogeneous, quasi-liquid protein environment. The identity of both difference patterns implies that the protonation of a model compound in solution causes a partial stretching of the geometry of the macrocycle as found in the protein. In fact, the similarity of the difference pattern within the bilin family for identical chemical transformations represents a basis for future theoretical analysis. On the other hand, the change of the (13)C NMR chemical shift pattern upon the Pr --> Pfr photoisomerization is very different to that of the free model compound upon ZZZ --> ZZE photoisomerization. Hence, the character of the double-bond isomerization in phytochrome is essentially different from that of a classical photoinduced double-bond isomerization, emphasizing the role of the protein environment in the modulation of this light-induced process. PMID:20492561

  4. Chemical bonding and dynamic fluxionality of a B15(+) cluster: a nanoscale double-axle tank tread.

    PubMed

    Wang, Ying-Jin; You, Xue-Rui; Chen, Qiang; Feng, Lin-Yan; Wang, Kang; Ou, Ting; Zhao, Xiao-Yun; Zhai, Hua-Jin; Li, Si-Dian

    2016-06-21

    A planar, elongated B15(+) cationic cluster is shown to be structurally fluxional and functions as a nanoscale tank tread on the basis of electronic structure calculations, bonding analyses, and molecular dynamics simulations. The outer B11 peripheral ring behaves like a flexible chain gliding around an inner B4 rhombus core, almost freely at the temperature of 500 K. The rotational energy barrier is only 1.37 kcal mol(-1) (0.06 eV) at the PBE0/6-311+G* level, further refined to 1.66 kcal mol(-1) (0.07 eV) at the single-point CCSD(T)/6-311G*//CCSD/6-311G* level. Two soft vibrational modes of 166.3 and 258.3 cm(-1) are associated with the rotation, serving as double engines for the system. Bonding analysis suggests that the "island" electron clouds, both σ and π, between the peripheral ring and inner core flow and shift continuously during the intramolecular rotation, facilitating the dynamic fluxionality of the system with a small rotational barrier. The B15(+) cluster, roughly 0.6 nm in dimension, is the first double-axle nanoscale tank tread equipped with two engines, which expands the concepts of molecular wheels, Wankel motors, and molecular tanks. PMID:27229290

  5. The Reductive Activation of CO2 Across a Ti=Ti Double Bond: Synthetic, Structural, and Mechanistic Studies

    PubMed Central

    2015-01-01

    The reactivity of the bis(pentalene)dititanium double-sandwich compound Ti2Pn†2 (1) (Pn† = 1,4-{SiiPr3}2C8H4) with CO2 is investigated in detail using spectroscopic, X-ray crystallographic, and computational studies. When the CO2 reaction is performed at −78 °C, the 1:1 adduct 4 is formed, and low-temperature spectroscopic measurements are consistent with a CO2 molecule bound symmetrically to the two Ti centers in a μ:η2,η2 binding mode, a structure also indicated by theory. Upon warming to room temperature the coordinated CO2 is quantitatively reduced over a period of minutes to give the bis(oxo)-bridged dimer 2 and the dicarbonyl complex 3. In situ NMR studies indicated that this decomposition proceeds in a stepwise process via monooxo (5) and monocarbonyl (7) double-sandwich complexes, which have been independently synthesized and structurally characterized. 5 is thermally unstable with respect to a μ-O dimer in which the Ti–Ti bond has been cleaved and one pentalene ligand binds in an η8 fashion to each of the formally TiIII centers. The molecular structure of 7 shows a “side-on” bound carbonyl ligand. Bonding of the double-sandwich species Ti2Pn2 (Pn = C8H6) to other fragments has been investigated by density functional theory calculations and fragment analysis, providing insight into the CO2 reaction pathway consistent with the experimentally observed intermediates. A key step in the proposed mechanism is disproportionation of a mono(oxo) di-TiIII species to yield di-TiII and di-TiIV products. 1 forms a structurally characterized, thermally stable CS2 adduct 8 that shows symmetrical binding to the Ti2 unit and supports the formulation of 4. The reaction of 1 with COS forms a thermally unstable complex 9 that undergoes scission to give mono(μ-S) mono(CO) species 10. Ph3PS is an effective sulfur transfer agent for 1, enabling the synthesis of mono(μ-S) complex 11 with a double-sandwich structure and bis(μ-S) dimer 12 in which the Ti

  6. Theoretical in-Solution Conformational/Tautomeric Analyses for Chain Systems with Conjugated Double Bonds Involving Nitrogen(s)

    PubMed Central

    Nagy, Peter I.

    2015-01-01

    Conformational/tautomeric transformations for X=CH–CH=Y structures (X = CH2, O, NH and Y = NH) have been studied in the gas phase, in dichloromethane and in aqueous solutions. The paper is a continuation of a former study where s-cis/s-trans conformational equilibria were predicted for analogues. The s-trans conformation is preferred for the present molecules in the gas phase on the basis of its lowest internal free energy as calculated at the B97D/aug-cc-pvqz and CCSD(T)CBS (coupled-cluster singles and doubles with non-iterative triples extrapolated to the complete basis set) levels. Transition state barriers are of 29–36 kJ/mol for rotations about the central C–C bonds. In solution, an s-trans form is still favored on the basis of its considerably lower internal free energy compared with the s-cis forms as calculated by IEF-PCM (integral-equation formalism of the polarizable continuum dielectric solvent model) at the theoretical levels indicated. A tetrahydrate model in the supermolecule/continuum approach helped explore the 2solute-solvent hydrogen bond pattern. The calculated transition state barrier for rotation about the C–C bond decreased to 27 kJ/mol for the tetrahydrate. Considering explicit solvent models, relative solvation free energies were calculated by means of the free energy perturbation method through Monte Carlo simulations. These calculated values differ remarkably from those by the PCM approach in aqueous solution, nonetheless the same prevalent conformation was predicted by the two methods. Aqueous solution structure-characteristics were determined by Monte Carlo. Equilibration of conformers/tautomers through water-assisted double proton-relay is discussed. This mechanism is not viable, however, in non-protic solvents where the calculated potential of mean force curve does not predict remarkable solute dimerization and subsequent favorable orientation. PMID:25984602

  7. Accurate Bond Energies of Hydrocarbons from Complete Basis Set Extrapolated Multi-Reference Singles and Doubles Configuration Interaction

    SciTech Connect

    Oyeyemi, Victor B.; Pavone, Michele; Carter, Emily A.

    2011-11-03

    Quantum chemistry has become one of the most reliable tools for characterizing the thermochemical underpinnings of reactions, such as bond dissociation energies (BDEs). The accurate prediction of these particular properties (BDEs) are challenging for ab initio methods based on perturbative corrections or coupled cluster expansions of the single-determinant Hartree-Fock wave function: the processes of bond breaking and forming are inherently multi-configurational and require an accurate description of non-dynamical electron correlation. To this end, we present a systematic ab initio approach for computing BDEs that is based on three components: (1) multi-reference single and double excitation configuration interaction (MRSDCI) for the electronic energies; (2) a two-parameter scheme for extrapolating MRSDCI energies to the complete basis set limit; and (3) DFT-B3LYP calculations of minimumenergy structures and vibrational frequencies to account for zero point energy and thermal corrections. We validated our methodology against a set of reliable experimental BDE values of C*C and C*H bonds of hydrocarbons. The goal of chemical accuracy is achieved, on average, without applying any empirical corrections to the MRSDCI electronic energies. We then use this composite scheme to make predictions of BDEs in a large number of hydrocarbon molecules for which there are no experimental data, so as to provide needed thermochemical estimates for fuel molecules.

  8. Synthesis of aza-fused polycyclic quinolines via double C-H bond activation.

    PubMed

    Huang, Ji-Rong; Dong, Lin; Han, Bo; Peng, Cheng; Chen, Ying-Chun

    2012-07-16

    Simple but efficient: Aza-fused polycyclic quinolines were efficiently assembled through rhodium(III)-based direct double C-H activation of N-aryl azoles followed by cyclization with alkynes without heteroatom-assisted chelation. Copper(II) acetate, aside from acting as an oxidant, could also play an important role in the C-H activation process. PMID:22715023

  9. Luminescent optical detection of volatile electron deficient compounds by conjugated polymer nanofibers.

    PubMed

    Wade, Aidan; Lovera, Pierre; O'Carroll, Deirdre; Doyle, Hugh; Redmond, Gareth

    2015-04-21

    Optical detection of volatile electron deficient analytes via fluorescence quenching is demonstrated using ca. 200 nm diameter template-synthesized polyfluorene nanofibers as nanoscale detection elements. Observed trends in analyte quenching effectiveness suggest that, in addition to energetic factors, analyte vapor pressure and polymer/analyte solubility play an important role in the emission quenching process. Individual nanofibers successfully act as luminescent reporters of volatile nitroaromatics at sub-parts per million levels. Geometric factors, relating to the nanocylindrical geometry of the fibers and to low nanofiber substrate coverage, providing a less crowded environment around fibers, appear to play a role in providing access by electron deficient quencher molecules to the excited states within the fibers, thereby facilitating the pronounced fluorescence quenching response. PMID:25803242

  10. Rhodium(II)-Catalyzed C-H Functionalization of Electron-Deficient Methyl Groups.

    PubMed

    Fu, Liangbing; Guptill, David M; Davies, Huw M L

    2016-05-11

    Enantioselective C-H functionalization of relatively electron-deficient methyl sites was achieved with the combination of 2,2,2-trichloroethyl aryldiazoacetates and tetrakis(triarylcyclopropanecarboxylate) dirhodium catalysts. The substrate scope of the transformation was relatively broad, and C-H functionalization products were furnished with excellent levels of enantioselectivity. As a strategic reaction, crotonate derivatives give 1,6-dicarbonyl compounds, which are useful for further diversification. PMID:27064173

  11. Copper-catalyzed oxyamination of electron-deficient alkenes with N-acyloxyamines.

    PubMed

    Ren, Shichao; Song, Shengjin; Ye, Lu; Feng, Chao; Loh, Teck-Peng

    2016-08-16

    A Cu(i)-catalyzed direct intermolecular oxyamination of electron deficient alkenes is disclosed. This process is characterized by difunctionalization of a variety of α,β-unsaturated ketones with easily available N-acyloxyamine reagents as both amine and oxygen donors, which delivers ester derivatives of β-amino alcohols in good yields as well as with high regioselectivity. Control studies suggested the involvement of alkyl radical species on the way of product formation. PMID:27481485

  12. Construction of hybrid material with double chemical bond from functional bridge ligand: Molecular modification, lotus root-like micromorphology and strong luminescence

    NASA Astrophysics Data System (ADS)

    Yan, Bing; Sui, Yu-Long

    2006-07-01

    Modifying benzoic acid with a cross-linking molecule (3-aminopropyl)triethoxysilane (abbreviated as APES), a fictional molecular bridge with double reactivity was achieved by the amidation reaction between them. Then the modified functional molecule, which behaving as a bridge, both coordinate with terbium ion through amide's oxygen atom and form the Si-O chemical bond in an in situ sol-gel process with matrix precursor (tetraethoxysilane, TEOS). As a result, a novel molecular hybrid material (Tb-BA-APES) with double chemical bond (Tb-O coordination bond and Si-O covalent bond) was constructed. The strong luminescence of Tb 3+ substantiates optimum energy couple and effective intramolecular energy transfer between the triplet state energy of modified ligand bridge and emissive energy level of Tb 3+. Especially SEM of the molecular hybrid material exhibits unexpected microlotus root-like pore morphology.

  13. The stereochemical outcome of electrophilic addition reactions on the 5,6-double bond in the spinosyns.

    PubMed

    De Amicis, C V; Graupner, P R; Erickson, J A; Paschal, J W; Kirst, H A; Creemer, L C; Fanwick, P E

    2001-12-14

    The electrophilic addition of reagents to the 5,6-double bond in spinosyn A and spinosyn D systems occurred with high pi-diastereofacial selectivity. Addition occurred preferentially from the beta face of the molecule with selectivities ranging from 5:1 to better than 30:1. Various NMR properties were investigated in order to distinguish the beta and alpha isomers with the help of theoretical models of the products. These NMR properties include a (13)C gamma effect to C-11 and vicinal coupling between H-4 and H-5. To help rationalize the selectivity, computational studies on the transition states for epoxidation were calculated using density functional theory. The results indicate that beta epoxidation is favored and that the geometries of the transition structures are consistent with torsional steering being the source of the selectivity. PMID:11735521

  14. Double proton transfer and one-electron oxidation behavior in double H-bonded glycinamide-glycine complex in the gas phase.

    PubMed

    Li, Ping; Bu, Yuxiang

    2005-04-30

    The behaviors of double proton transfer (DPT) occurring in a representative glycinamide-glycine complex have been investigated employing the B3LYP/6-311++G** level of theory. Thermodynamic and especially kinetic parameters, such as tautomerization energy, equilibrium constant, and barrier heights have been discussed, respectively. The relevant quantities involved in the DPT process including geometrical changes, interaction energies, and deformation energies have also been studied. Analogous to that of tautomeric process assisted with a formic acid molecule, the participation of a glycine molecule favors the proceeding of the proton transfer (PT) for glycinamide compared with that without mediator-assisted case. The DPT process proceeds with a concerted mechanism rather than a stepwise one because no zwitterionic complexes have been located during the DPT process. The barrier heights are 12.14 and 0.83 kcal/mol for the forward and reverse directions, respectively. However, both of them have been reduced by 3.10 and 2.66 kcal/mol to 9.04 and -1.83 kcal/mol with further inclusion of zero-point vibrational energy (ZPVE) corrections, where the disappearance of the reverse barrier height implies that the reverse reaction should proceed with barrierless spontaneously, analogous to those of DPTs occurring between glycinamide and formic acid (or formamide). Additionally, the oxidation process for the double H-bonded glycinamide-glycine complex has also been investigated. The oxidated product is characterized by a distonic radical cation due to the fact that one-electron oxidation takes place on glycine fragment and a proton has been transferred from glycine to glycinamide fragment spontaneously. As a result, the vertical and adiabatic ionization potentials for the neutral complex have been determined to be about 8.71 and 7.85 eV, respectively, where both of them have been reduced by about 0.54 (1.11) and 0.75 (1.13) eV relative to those of isolated glycinamide (glycine

  15. A monotopic aluminum telluride with an Al=Te double bond stabilized by N-heterocyclic carbenes

    PubMed Central

    Franz, Daniel; Szilvási, Tibor; Irran, Elisabeth; Inoue, Shigeyoshi

    2015-01-01

    Aluminum chalcogenides are mostly encountered in the form of bulk aluminum oxides that are structurally diverse but typically consist of networks with high lattice energy in which the chalcogen atoms bridge the metal centres. This makes their molecular congeners difficult to synthesize because of a pronounced tendency for oligomerization. Here we describe the isolation of the monotopic aluminum chalcogenide (LDipN)AlTe(LEt)2 (LDip=1,3-(2,6-diisopropylphenyl)-imidazolin-2-imine, LEt=1,3-diethyl-4,5-dimethyl-imidazolin-2-ylidene). Unique features of (LDipN)AlTe(LEt)2 are the terminal position of the tellurium atom, the shortest aluminum–tellurium distance hitherto reported for a molecular complex and the highest bond order reported for an interaction between these elements, to the best of our knowledge. At elevated temperature (LDipN)AlTe(LEt)2 equilibrates with dimeric {(LDipN)AlTe(LEt)}2 in which the chalcogen atoms assume their common role as bridges between the metal centres. These findings demonstrate that (LDipN)AlTe(LEt)2 comprises the elusive Al=Te double bond in the form of an N-heterocyclic carbene-stabilized species. PMID:26612781

  16. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Tsukanov, A. A.; Psakhie, S. G.

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered.

  17. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

    PubMed Central

    Tsukanov, A.A.; Psakhie, S.G.

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered. PMID:26817816

  18. Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study.

    PubMed

    Tsukanov, A A; Psakhie, S G

    2016-01-01

    The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered. PMID:26817816

  19. Dependence of bonding interactions in Layered Double Hydroxides on metal cation chemistry

    NASA Astrophysics Data System (ADS)

    Shamim, Mostofa; Dana, Kausik

    2016-12-01

    The evolution of various Infrared bands of Layered Double Hydroxides (LDH) with variable Zn:Al ratio was analyzed to correlate it with the changes in octahedral metal cation chemistry, interlayer carbonate anion and hydroxyl content of LDH. The synthesized phase-pure LDHs were crystallized as hexagonal 2H polytype with a Manasseite structure. The broad and asymmetric hydroxyl stretching region (2400-4000 cm-1) can be deconvoluted into four different bands. With increase in Zn2+:Al3+ metal ratio, the peak position of stretching frequencies of Al3+sbnd OH and carbonate-bridged hydroxyl (water) decrease almost linearly. Individual band's peak position and area under the curve have been successfully correlated with the carbonate and hydroxyl content of LDH. Due to lowering of symmetry of the carbonate anion, the IR-inactive peak νCsbnd O, symm at 1064 cm-1 becomes IR active. The peak position of metal-oxygen bands and carbonate bending modes are practically unaffected by the Zn2+:Al3+ ratio but the area under the individual M-O bands shows a direct correlation.

  20. Quantitative assessment of the multiplicity of carbon-halogen bonds: carbenium and halonium ions with F, Cl, Br, and I.

    PubMed

    Kalescky, Robert; Zou, Wenli; Kraka, Elfi; Cremer, Dieter

    2014-03-13

    CX (X = F, Cl, Br, I) and CE bonding (E = O, S, Se, Te) was investigated for a test set of 168 molecules using the local CX and CE stretching force constants k(a) calculated at the M06-2X/cc-pVTZ level of theory. The stretching force constants were used to derive a relative bond strength order (RBSO) parameter n. As alternative bond strength descriptors, bond dissociation energies (BDE) were calculated at the G3 level or at the two-component NESC (normalized elimination of the small component)/CCSD(T) level of theory for molecules with X = Br, I or E = Se, Te. RBSO values reveal that both bond lengths and BDE values are less useful when a quantification of the bond strength is needed. CX double bonds can be realized for Br- or I-substituted carbenium ions where as suitable reference the double bond of the corresponding formaldehyde homologue is used. A triple bond cannot be realized in this way as the diatomic CX(+) ions with a limited π-donor capacity for X are just double-bonded. The stability of halonium ions increases with the atomic number of X, which is reflected by a strengthening of the fractional (electron-deficient) CX bonds. An additional stability increase of up to 25 kcal/mol (X = I) is obtained when the X(+) ion can form a bridged halonium ion with ethene such that a more efficient 2-electron-3-center bonding situation is created. PMID:24555526

  1. Radical formation in the FMN-photosensitized reactions of unsaturated fatty acids bearing double bonds at different positions.

    PubMed

    Nishihama, Nao; Iwahashi, Hideo

    2016-08-15

    Although the reaction mechanisms through which flavin mononucleotide works as an endogenous photosensitizer have been investigated (Baier et al., 2006; Edwards and Silva, 2001; Pajares et al., 2001; Criado et al., 2003; Massad et al., 2008) [23-27], few studies have been performed for the reactions of flavin mononucleotide with unsaturated fatty acids. To examine the reactions of flavin mononucleotide with unsaturated fatty acids bearing a double bond at different positions, an electron spin resonance, a high performance liquid chromatography-electron spin resonance and a high performance liquid chromatography-electron spin resonance-mass spectrometry were employed. The control reaction mixtures contained 25μmolL(-1) of flavin mononucleotide, 1.0mmolL(-1) of FeSO4(NH4)2SO4, 10mmolL(-1) of cholic acid, 30mmolL(-1) of phosphate buffer (pH 7.4) and 0.1molL(-1) of α-(4-pyridyl-1-oxide)-N-tert-butylnitrone in deuterium oxide. In addition, it also contained 4.3mmolL(-1) of one of the following: (z)-11-octadecenoic acid, (z)-6-octadecenoic acid, (z)-9-octadecenoic acid or (z, z)-9, 12-octadecadienoic acid. The control reaction mixtures without FeSO4(NH4)2SO4 and α-(4-pyridyl-1-oxide)-N-tert-butylnitrone were exposed to the visible light at 436nm (7.8Jcm(-2)). After the irradiation, α-(4-pyridyl-1-oxide)-N-tert-butylnitrone was added. The reactions started from adding FeSO4(NH4)2SO4 and performed at 25°C for 1min. Electron spin resonance measurements of the control reaction mixtures showed prominent signals (α(N)=1.58mT and α(Hβ)=0.26mT). High performance liquid chromatography-electron spin resonance analyses of the control reaction mixtures showed prominent peaks at the retention times of 31.1min {(z)-6-octadecenoic acid}, 39.6min {(z)-9-octadecenoic acid}, 44.9min {(z)-11-octadecenoic acid} and 40.2min {(z, z)-9, 12-octadecadienoic acid}. High performance liquid chromatography-electron spin resonance-mass analyses of the control reaction mixtures showed that 4

  2. Bridging gold in electron-deficient Al2Au(n)(0/-) and BAlAu(n)(0/-) (n = 1-3) clusters.

    PubMed

    Yao, Wen-Zhi; Liu, Bing-Tao; Lu, Zhang-Hui; Li, Si-Dian

    2013-06-20

    The geometrical and electronic structures of the electron-deficient dialuminum aurides Al2Aun(0/-) and hybrid boron-aluminum aurides BAlAun(0/-) (n = 1-3) are systematically investigated based on the density and wave function theories. Ab initio theoretical evidence strongly suggests that bridging gold atoms exist in the ground states of C2v Al2Au(-) ((3)B1), C2v Al2Au ((2)B1), C2v Al2Au2(-) ((2)A1), C2v Al2Au2 ((1)A1), Cs Al2Au3(-) ((1)A'), and D3h Al2Au3 ((2)A1), which prove to possess an Al-Au-Al τ bond. For BAlAun(0/-) (n = 1-3) mixed clusters, bridging B-Au-Al units only exist in Cs BAlAu3(-) ((1)A') and Cs BAlAu3 ((2)A'), whereas Cs BAlAu(-) ((3)A''), Cs BAlAu ((2)A''), Cs BAlAu2(-) ((2)A'), and Cs BAlAu2 ((1)A') do not possess a bridging gold, as demonstrated by the fact that B-Al and B-Au exhibit significantly stronger electronic interaction than Al-Au in the same clusters. Orbital analyses indicate that Au 6s contributes approximately 98%-99% to the Au-based orbital in these Al-Au-Al/B-Au-Al interactions, whereas Au 5d contributes 1%-2%. The adiabatic and vertical detachment energies of Al2Aun(-) (n = 1-3) are calculated to facilitate future experimental characterizations. The results obtained in this work establish an interesting τ bonding model (Al-Au-Al/B-Au-Al) for electron-deficient systems in which Au 6s plays a major factor. PMID:23718624

  3. A method of coupling the Paternò-Büchi reaction with direct infusion ESI-MS/MS for locating the C[double bond, length as m-dash]C bond in glycerophospholipids.

    PubMed

    Stinson, Craig A; Xia, Yu

    2016-06-21

    Tandem mass spectrometry (MS/MS) coupled with soft ionization is established as an essential platform for lipid analysis; however, determining high order structural information, such as the carbon-carbon double bond (C[double bond, length as m-dash]C) location, remains challenging. Recently, our group demonstrated a method for sensitive and confident lipid C[double bond, length as m-dash]C location determination by coupling online the Paternò-Büchi (PB) reaction with nanoelectrospray ionization (nanoESI) and MS/MS. Herein, we aimed to expand the scope of the PB reaction for lipid analysis by enabling the reaction with infusion ESI-MS/MS at much higher flow rates than demonstrated in the nanoESI setup (∼20 nL min(-1)). In the new design, the PB reaction was effected in a fused silica capillary solution transfer line, which also served as a microflow UV reactor, prior to ESI. This setup allowed PB reaction optimization and kinetics studies. Under optimized conditions, a maximum of 50% PB reaction yield could be achieved for a standard glycerophosphocholine (PC) within 6 s of UV exposure over a wide flow rate range (0.1-10 μL min(-1)). A solvent composition of 7 : 3 acetone : H2O (with 1% acid or base modifier) allowed the highest PB yields and good lipid ionization, while lower yields were obtained with an addition of a variety of organic solvents. Radical induced lipid peroxidation was identified to induce undesirable side reactions, which could be effectively suppressed by eliminating trace oxygen in the solution via N2 purge. Finally, the utility of coupling the PB reaction with infusion ESI-MS/MS was demonstrated by analyzing a yeast polar lipid extract where C[double bond, length as m-dash]C bond locations were revealed for 35 glycerophospholipids (GPs). PMID:26892746

  4. An Electron-Deficient Building Block Based on the B←N Unit: An Electron Acceptor for All-Polymer Solar Cells.

    PubMed

    Dou, Chuandong; Long, Xiaojing; Ding, Zicheng; Xie, Zhiyuan; Liu, Jun; Wang, Lixiang

    2016-01-22

    A double B←N bridged bipyridyl (BNBP) is a novel electron-deficient building block for polymer electron acceptors in all-polymer solar cells. The B←N bridging units endow BNBP with fixed planar configuration and low-lying LUMO/HOMO energy levels. As a result, the polymer based on BNBP units (P-BNBP-T) exhibits high electron mobility, low-lying LUMO/HOMO energy levels, and strong absorbance in the visible region, which is desirable for polymer electron acceptors. Preliminary all-polymer solar cell (all-PSC) devices with P-BNBP-T as the electron acceptor and PTB7 as the electron donor exhibit a power conversion efficiency (PCE) of 3.38%, which is among the highest values of all-PSCs with PTB7 as the electron donor. PMID:26663513

  5. Cholesterol interactions with tetracosenoic acid phospholipids in model cell membranes: role of the double-bond position.

    PubMed

    Ayanoglu, E; Chiche, B H; Beatty, M; Djerassi, C; Düzgüneş, N

    1990-04-10

    The synthesis and thermotropic properties of 1,2-di-(9Z)-9-tetracosenoylphosphatidylcholine [delta 9-PC(24:1,24:1), 1], 1,2-di-(5Z)-5-tetracosenoylphosphatidylcholine [delta 5-PC(24:1,24:1), 2], and 1,2-di-(15Z)-15- tetracosenoylphosphatidylcholine [delta 15-PC(24:1,24:1), 3] are reported. Liposomes prepared from these phospholipids differ from those of the natural sponge phospholipids, 1,2-di-(5Z,9Z)-5,9-hexacosadienoylphosphatidylcholine (4a) and the corresponding ethanolamine (4b), both of which virtually exclude cholesterol from their bilayers. The behavior of 1 and 2 is similar to that of 1,2-di-(6Z,9Z)-6,9-hexacosadienoylphosphatidylcholine (5), which exhibits a partial molecular interaction with cholesterol. In the case of 3, cholesterol appears to interact with the saturated acyl chain regions of this phospholipid in a manner similar to that of its interaction with DPPC acyl chains. This study delineates the effect of the double-bond location in long fatty acyl chains of phospholipids on their interactions with cholesterol. PMID:2354147

  6. Boron- and Nitrogen-Doped Phenalenyls: Unexpected 2e/ and 4e/all-sites pi-pi Covalency and Genuine Pancake Double Bonding

    DOE PAGESBeta

    Tian, Yong-Hui; Huang, Jingsong; Sumpter, Bobby G

    2015-01-01

    Phenalenyl is an important neutral pi-radical due to its capability to form unconventional pancake pi-pi bonding interactions, whereas its analogues with graphitic boron (B) or nitrogen (N)-doping have been regarded as closed-shell systems and therefore received much less attention. By using high-level quantum chemistry calculations, we show that the B- and N-doped closed-shell phenalenyls unexpectedly form open-shell singlet pi-dimers with diradicaloid character featuring 2e/all-sites double pi-pi bonding. Moreover, by proper substitutions, the doped phenalenyl derivatives can be made open-shell species that form closed shell singlet pi-dimers bound by stronger 4e/all-sites double pi-pi bonding. The covalent pi-pi bonding overlap is distributedmore » on all of the atomic sites giving robust and genuine pancake-shaped pi-dimers which, depending on the number of electrons available in the bonding interactions, are equally or more stable than the pi-dimers of the pristine phenalenyl.« less

  7. C-H activation and C=C double bond formation reactions in iridium ortho-methyl arylphosphane complexes.

    PubMed

    Baratta, Walter; Ballico, Maurizio; Del Zotto, Alessandro; Zangrando, Ennio; Rigo, Pierluigi

    2007-01-01

    The Vaska-type iridium(I) complex [IrCl(CO){PPh(2)(2-MeC(6)H(4))}(2)] (1), characterized by an X-ray diffraction study, was obtained from iridium(III) chloride hydrate and PPh(2)(2,6-MeRC(6)H(3)) with R=H in DMF, whereas for R=Me, activation of two ortho-methyl groups resulted in the biscyclometalated iridium(III) compound [IrCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)] (2). Conversely, for R=Me the iridium(I) compound [IrCl(CO){PPh(2)(2,6-Me(2)C(6)H(3))}(2)] (3) can be obtained by treatment of [IrCl(COE)(2)](2) (COE=cyclooctene) with carbon monoxide and the phosphane in acetonitrile. Compound 3 in CH(2)Cl(2) undergoes intramolecular C-H oxidative addition, affording the cyclometalated hydride iridium(III) species [IrHCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}] (4). Treatment of 2 with Na[BAr(f) (4)] (Ar(f)=3,5-C(6)H(3)(CF(3))(2)) gives the fluxional cationic 16-electron complex [Ir(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)][BAr(f) (4)] (5), which reversibly reacts with dihydrogen to afford the delta-agostic complex [IrH(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}][BAr(f)(4)] (6), through cleavage of an Ir-C bond. This species can also be formed by treatment of 4 with Na[BAr(f)(4)] or of 2 with Na[BAr(f)(4)] through C-H oxidative addition of one ortho-methyl group, via a transient 14-electron iridium(I) complex. Heating of the coordinatively unsaturated biscyclometalated species 5 in toluene gives the trans-dihydride iridium(III) complex [IrH(2)(CO){PPh(2)(2,6-MeC(6)H(3)CH=CHC(6)H(3)Me-2,6)PPh(2)}][BAr(f) (4)] (7), containing a trans-stilbene-type terdentate ligand, as result of a dehydrogenative carbon-carbon double bond coupling reaction, possibly through an iridium carbene species. PMID:17535000

  8. Phosphate-intercalated Ca-Fe-layered double hydroxides: Crystal structure, bonding character, and release kinetics of phosphate

    SciTech Connect

    Woo, Myong A.; Woo Kim, Tae; Paek, Mi-Jeong; Ha, Hyung-Wook; Choy, Jin-Ho; Hwang, Seong-Ju

    2011-01-15

    The nitrate-form of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca-Fe-LDH-NO{sub 3}{sup -} compound and its H{sub 2}PO{sub 4}{sup -}-intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO{sub 4}{sup 2-} caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca-Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO{sub 4}{sup 2-} and H{sub 2}PO{sub 4}{sup -}. Under acidic conditions, phosphate ions were slowly released from the Ca-Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca-Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil. -- Graphical abstract: We synthesized phosphate-intercalated Ca-Fe-LDH materials that can act as bifunctional inorganic vectors for the slow release of phosphate fertilizer and also the neutralization of acid soil. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. Display Omitted Research Highlights: {yields} The phosphate forms of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) were synthesized via co-precipitation method. The crystal structure, bonding character, and release kinetics of phosphate of the phosphate-intercalates were investigated. These Ca-Fe-LDH materials are applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.

  9. Development of a three-steps derivatization assay for the localization of double bond in monounsaturated monomers of poly-beta-hydroxyalkanoates by GC-MS.

    PubMed

    Simon-Colin, Christelle; Gouin, Christelle; Lemechko, Pierre; Kervarec, Nelly; Guezennec, Jean

    2012-07-01

    A new gas chromatography-mass spectrometry (GC-MS) method for the localization of double bond in monounsaturated 3-hydroxyalkenoic acids monomers has been developed. A three steps derivation assay was used including a methanolysis, then acetylation and dimethyldisulfide (DMDS) addition to alkene groups. Electron impact GC-MS analysis of such derivatives offers characteristic fragments allowing the unambiguous determination of double bond position in side chain. This novel method is well-suited for the routine analysis of poly-beta-hydroxyalkanoates (PHAs), and was used to characterize monounsaturated monomers in both 3-hydroxyalkenoic acids standards as well as in mcl-PHAs and poly(3-hydroxyoctanoate-co-3-hydroxyundecenoate) (PHOU) produced by bacterial strain Pseudomonas guezennei from glucose or a mixture of sodium octanoate plus 10-undecenoic acid, respectively. PMID:22717557

  10. Ultrafast excited state relaxation dynamics of electron deficient porphyrins: Conformational and electronic factors

    NASA Astrophysics Data System (ADS)

    Okhrimenko, Albert N.

    Metallo-tetrapyrroles (MTP) are highly stable macrocyclic pi-systems that display interesting properties that make them potential candidates for various applications. Among these applications are optoelectronics, magnetic materials, photoconductive materials, non-linear optical materials and photo tumor therapeutic drugs. These applications are generally related to their high stability and efficient light absorption ability in the visible and near-infrared region of the optical spectrum. Metallo porphyrins are well known and widely studied representatives of metallotetrapyrroles. Electron deficient substituents in the meso positions are well known to greatly influence the interaction between the metal d-orbitals and the nitrogen orbitals of the tetrapyrrole macrocycle. In this work, a series of electron deficient porphyrins has been studied to gain some knowledge about the change in the excited state dynamics with structural and electronic modifications. Among these porphyrins is nickel and iron modified species bearing perfluoro-, perprotio-, p-nitrophenyl- and perfluorophenyl-meso substituents. Ultrafast transient absorption spectrometry has been used as the main research instrument along with other spectroscopic and electrochemical methods. A new technique has been employed to study the photophysical properties of zinc (II) tetraphenylporphine cation radical. It employs a combination of controlled potential coulometry and femtosecond absorption spectrometry. The fast transient lifetime of 17 ps of the pi-cation species originates in very efficient mixing of the a2u HOMO cation orbital that places electronic density mainly on pyrrolic nitrogens and metal d-orbitals. That explains the lack of any emission of the cationic species. This non-radiative decay process might elucidate the processes taking place in photosynthetic systems when electron is removed from porphyrinic moiety and the hole is produced. In this work zinc(II) meso-tetraphenylporphine radial cation

  11. Synthesis of -C[double bond, length as m-dash]N- linked covalent organic frameworks via the direct condensation of acetals and amines.

    PubMed

    Li, Zhi-Jun; Ding, San-Yuan; Xue, Hua-Dong; Cao, Wei; Wang, Wei

    2016-06-01

    We demonstrate herein a facile approach for constructing -C[double bond, length as m-dash]N- linked COFs from acetals. Three new COFs (imine-linked LZU-20, hydrazone-linked LZU-21, and azine-linked LZU-22) were synthesized by the direct condensation of dimethyl acetals and amines. All the synthesized COFs are highly crystalline and exhibit good thermal stability. PMID:27090755

  12. Origin of the 900 cm{sup −1} broad double-hump OH vibrational feature of strongly hydrogen-bonded carboxylic acids

    SciTech Connect

    Van Hoozen, Brian L.; Petersen, Poul B.

    2015-03-14

    Medium and strong hydrogen bonds are common in biological systems. Here, they provide structural support and can act as proton transfer relays to drive electron and/or energy transfer. Infrared spectroscopy is a sensitive probe of molecular structure and hydrogen bond strength but strongly hydrogen-bonded structures often exhibit very broad and complex vibrational bands. As an example, strong hydrogen bonds between carboxylic acids and nitrogen-containing aromatic bases commonly display a 900 cm{sup −1} broad feature with a remarkable double-hump structure. Although previous studies have assigned this feature to the OH, the exact origin of the shape and width of this unusual feature is not well understood. In this study, we present ab initio calculations of the contributions of the OH stretch and bend vibrational modes to the vibrational spectrum of strongly hydrogen-bonded heterodimers of carboxylic acids and nitrogen-containing aromatic bases, taking the 7-azaindole—acetic acid and pyridine—acetic acid dimers as examples. Our calculations take into account coupling between the OH stretch and bend modes as well as how both of these modes are affected by lower frequency dimer stretch modes, which modulate the distance between the monomers. Our calculations reproduce the broadness and the double-hump structure of the OH vibrational feature. Where the spectral broadness is primarily caused by the dimer stretch modes strongly modulating the frequency of the OH stretch mode, the double-hump structure results from a Fermi resonance between the out of the plane OH bend and the OH stretch modes.

  13. Analysis of diacylglycerols by ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry: Double bond location and isomers separation.

    PubMed

    Deng, Pan; Zhong, Dafang; Wang, Xi; Dai, Yulu; Zhou, Lei; Leng, Ying; Chen, Xiaoyan

    2016-06-21

    Diacylglycerols (DAGs) are important lipid intermediates and have been implicated in human diseases. Isomerism complicates their mass spectrometric analysis; in particular, it is difficult to identify fatty acid substituents and locate the double bond positions in unsaturated DAGs. We have developed an analytical strategy using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF MS) in conjunction with dimethyl disulfide (DMDS) derivatization and collision cross-section (CCS) measurement to characterize DAGs in biological samples. The method employs non-aqueous reversed-phase chromatographic separation and profile collision energy (CE) mode for MS(E) and MS/MS analyses. Three types of fragment ions were produced simultaneously. Hydrocarbon ions (m/z 50-200) obtained at high CE helped to distinguish unsaturated and saturated DAGs rapidly. Neutral loss ions and acylium ions (m/z 300-400) produced at low CE were used to identify fatty acid substituents. Informative methyl thioalkane fragment ions were used to locate the double bonds of unsaturated DAGs. Mono-methylthio derivatives were formed mainly by the reaction of DAGs with DMDS, where methyl thiol underwent addition to the first double bond farthest from the ester terminus of unsaturated fatty acid chains. The addition of CCS values maximized the separation of isomeric DAG species and improved the confidence of DAG identification. Fourteen DAGs were identified in mouse myotube cells based on accurate masses, characteristic fragment ions, DMDS derivatization, and CCS values. PMID:27188314

  14. Mechanistic and structural studies of apoform, binary, and ternary complexes of the Arabidopsis alkenal double bond reductase At5g16970.

    PubMed

    Youn, Buhyun; Kim, Sung-Jin; Moinuddin, Syed G A; Lee, Choonseok; Bedgar, Diana L; Harper, Athena R; Davin, Laurence B; Lewis, Norman G; Kang, Chulhee

    2006-12-29

    In this study, we determined the crystal structures of the apoform, binary, and ternary complexes of the Arabidopsis alkenal double bond reductase encoded by At5g16970. This protein, one of 11 homologues in Arabidopsis thaliana, is most closely related to the Pinus taeda phenylpropenal double bond reductase, involved in, for example, heartwood formation. Both enzymes also have essential roles in plant defense, and can function by catalyzing the reduction of the 7-8-double bond of phenylpropanal substrates, such as p-coumaryl and coniferyl aldehydes in vitro. At5g16970 is also capable of reducing toxic substrates with the same alkenal functionality, such as 4-hydroxy-(2E)-nonenal. The overall fold of At5g16970 is similar to that of the zinc-independent medium chain dehydrogenase/reductase superfamily, the members of which have two domains and are dimeric in nature, i.e. in contrast to their original classification as being zinc-containing oxidoreductases. As provisionally anticipated from the kinetic data, the shape of the binding pocket can readily accommodate p-coumaryl aldehyde, coniferyl aldehyde, 4-hydroxy-(2E)-nonenal, and 2-alkenals. However, the enzyme kinetic data among these potential substrates differ, favoring p-coumaryl aldehyde. Tyr-260 is provisionally proposed to function as a general acid/base for hydride transfer. A catalytic mechanism for this reduction, and its applicability to related important detoxification mammalian proteins, is also proposed. PMID:17028190

  15. Comparison of the kinetics and thermodynamics for methyl radical addition to C=C, C=O, and C=S double bonds.

    PubMed

    Henry, David J; Coote, Michelle L; Gómez-Balderas, Rodolfo; Radom, Leo

    2004-02-18

    The barriers, enthalpies, and rate constants for the addition of methyl radical to the double bonds of a selection of alkene, carbonyl, and thiocarbonyl species (CH(2)=Z, CH(3)CH=Z, and (CH(3))(2)C=Z, where Z = CH(2), O, or S) and for the reverse beta-scission reactions have been investigated using high-level ab inito calculations. The results are rationalized with the aid of the curve-crossing model. The addition reactions proceed via early transition structures in all cases. The barriers for addition of methyl radical to C=C bonds are largely determined by the reaction exothermicities. Addition to the unsubstituted carbon center of C=C double bonds is favored over addition to the substituted carbon center, both kinetically (lower barriers) and thermodynamically (greater exothermicities). The barriers for addition to C=O bonds are influenced by both the reaction exothermicity and the singlet-triplet gap of the substrate. Addition to the carbon center is favored over addition to the oxygen, also both thermodynamically and kinetically. For the thiocarbonyl systems, addition to the carbon center is thermodynamically favored over addition to sulfur. However, in this case, the reaction is contrathermodynamic, addition to the sulfur center having a lower barrier due to spin density considerations. Entropic differences among corresponding addition and beta-scission reactions are relatively minor, and the differences in reaction rates are thus dominated by differences in the respective reaction barriers. PMID:14871104

  16. The position effect of electron-deficient quinoxaline moiety in porphyrin based sensitizers

    NASA Astrophysics Data System (ADS)

    Fan, Suhua; Lv, Kai; Sun, Hong; Zhou, Gang; Wang, Zhong-Sheng

    2015-04-01

    An electron-deficient group, 2,3-diphenylquinoxaline (DPQ), is incorporated as an auxiliary acceptor into the different positions of the porphyrin (Por) based donor-π bridge-acceptor (D-π-A) dye (FNE57) to construct D-A‧-Por-π-A (FNE58) and D-Por-A‧-π-A (FNE59) configurations. The incorporation of DPQ unit between the donor and porphyrin unit has negligible influence on the absorption property, whereas the DPQ unit located between the porphyrin unit and acceptor significantly increases the absorbance for the Soret band and the valley between the Soret and Q bands. Theoretical calculation reveals that incorporating the DPQ unit adjacent to the acceptor is more advantageous to delocalize the lowest unoccupied molecular orbital and enhance the electronic asymmetry, which facilitates the intramolecular charge transfer. The effect of DPQ unit and its linkage position on the performance of related quasi-solid-state dye-sensitized solar cells (DSSCs) is systematically investigated. The quasi-solid-state DSSC with sensitizer FNE59 displays a power conversion efficiency of 6.02%, which is 23% and 51% higher than those for FNE57 and FNE58 based DSSCs. Our studies facilitate the understanding of the crucial importance of molecular engineering and pave a new path to design novel porphyrin based sensitizers for highly efficient DSSCs.

  17. Localization of Fatty Acyl and Double Bond Positions in Phosphatidylcholines Using a Dual Stage CID Fragmentation Coupled with Ion Mobility Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Castro-Perez, Jose; Roddy, Thomas P.; Nibbering, Nico M. M.; Shah, Vinit; McLaren, David G.; Previs, Stephen; Attygalle, Athula B.; Herath, Kithsiri; Chen, Zhu; Wang, Sheng-Ping; Mitnaul, Lyndon; Hubbard, Brian K.; Vreeken, Rob J.; Johns, Douglas G.; Hankemeier, Thomas

    2011-09-01

    A high content molecular fragmentation for the analysis of phosphatidylcholines (PC) was achieved utilizing a two-stage [trap (first generation fragmentation) and transfer (second generation fragmentation)] collision-induced dissociation (CID) in combination with travelling-wave ion mobility spectrometry (TWIMS). The novel aspects of this work reside in the fact that a TWIMS arrangement was used to obtain a high level structural information including location of fatty acyl substituents and double bonds for PCs in plasma, and the presence of alkali metal adduct ions such as [M + Li]+ was not required to obtain double bond positions. Elemental compositions for fragment ions were confirmed by accurate mass measurements. A very specific first generation fragment ion m/z 577 (M-phosphoryl choline) from the PC [16:0/18:1 (9Z)] was produced, which by further CID generated acylium ions containing either the fatty acyl 16:0 (C15H31CO+, m/z 239) or 18:1 (9Z) (C17H33CO+, m/z 265) substituent. Subsequent water loss from these acylium ions was key in producing hydrocarbon fragment ions mainly from the α-proximal position of the carbonyl group such as the hydrocarbon ion m/z 67 (+H2C-HC = CH-CH = CH2). Formation of these ions was of important significance for determining double bonds in the fatty acyl chains. In addition to this, and with the aid of 13C labeled lyso-phosphatidylcholine (LPC) 18:1 (9Z) in the ω-position (methyl) TAP fragmentation produced the ion at m/z 57. And was proven to be derived from the α-proximal (carboxylate) or distant ω-position (methyl) in the LPC.

  18. Collision-Induced Dissociation of Fatty Acid [M - 2H + Na]- Ions: Charge-Directed Fragmentation and Assignment of Double Bond Position

    NASA Astrophysics Data System (ADS)

    Thomas, Michael C.; Altvater, Jens; Gallagher, Thomas J.; Nette, Geoffrey W.

    2014-08-01

    The collision-induced dissociation (CID) of cationic fatty acid-metal ion complexes has been extensively studied and, in general, provides rich structural information. In particular, charge-remote fragmentation processes are commonly observed allowing the assignment of double bond position. In a previous manuscript, we presented two methods to doubly deprotonate polyunsaturated fatty acids to form anionic fatty acid-sodium ion complexes, referred to as [M - 2H + Na] - ions. In the current manuscript, the CID behavior of these [M - 2H + Na] - ions is investigated for the first time. Significantly, we also present a deuterium-labeling experiment, which excludes the possibility that deprotonation occurs predominately at the α-carbon in the formation of fatty acid [M - H + NaF]- ions. This supports our original proposal where deprotonation occurs at the bis-allylic positions of polyunsaturated fatty acids. CID spectra of polyunsaturated fatty acid [M - 2H + Na]- ions display abundant product ions arising from acyl chain cleavages. Through the examination of fatty acid isomers, it is demonstrated that double bond position may be unequivocally determined for methylene-interrupted polyunsaturated fatty acids with three or more carbon-carbon double bonds. In addition, CID of [M - 2H + Na]- ions was applied to 18:3 isomers of Nannochloropsis oculata and three isomers were tentatively identified: ∆9,12,1518:3, ∆6,9,1218:3, and ∆5,8,1118:3. We propose that structurally-informative product ions are formed via charge-driven fragmentation processes at the site of the resonance-stabilized carbanion as opposed to charge-remote fragmentation processes, which could be inferred if deprotonation occurred predominately at the α-carbon.

  19. Reactions of organoaluminum compounds with acetylene as a method for the synthesis of aliphatic derivatives with a z-disubstituted double bond

    SciTech Connect

    Andreeva, N.I.; Kuchin, A.V.; Tolstikov, G.A.

    1985-11-01

    This paper develops a method for the synthesis of aliphatic compounds with a Z-disubstituted double bond, which are important synthons for the preparation of such natural products as insect pheromones, aromatic principles, etc. In the carbalumination reaction of acetylene Z-alkenyldialkylaluminums are formed selectively. A-Alkenyldialkylaluminums are highly reactive and can readily be converted into Z-allyl alcohols and their ethers, and into Z-iodovinyl derivatives. By the reactions of vinyl organoaluminum compounds with the complex CH/sub 3/COClhaAlCl/sub 3/ E-conjugated ketones were obtained.

  20. Infrared spectroscopic studies on 4-amino-6-oxopyrimidine in a low-temperature Xe matrix and crystalline polymorphs composed of double hydrogen-bonded ribbons

    NASA Astrophysics Data System (ADS)

    Ohyama, Kazuko; Goto, Kenta; Shinmyozu, Teruo; Yamamoto, Norifumi; Iizumi, Shota; Miyagawa, Masaya; Nakata, Munetaka; Sekiya, Hiroshi

    2014-03-01

    Infrared (IR) spectra of the enol and keto forms of 4-amino-6-oxopyrimidine (AOP) isolated in a low-temperature Xe matrix were recorded, where the change from the keto to the enol form was found to be induced by UV irradiation (λ > 270 nm). On the other hand, the hydrated crystal of AOP exhibited a similar IR spectrum to the anhydrous crystal by dehydration, suggesting that the dehydrated and anhydrous crystals are polymorphs. It has been found from the IR spectral analyses that the AOP crystal is dominated by infinite double H-bonded ribbons, which has been supported by quantum chemical calculations.

  1. Formation of the Δ18,19 Double Bond and Bis(spiroacetal) in Salinomycin Is Atypically Catalyzed by SlnM, a Methyltransferase‐like Enzyme†

    PubMed Central

    Jiang, Chunyan; Qi, Zhen; Kang, Qianjin; Liu, Jing; Jiang, Ming

    2015-01-01

    Abstract Salinomycin is a widely used polyether coccidiostat and was recently found to have antitumor activities. However, the mechanism of its biosynthesis remained largely speculative until now. Reported herein is the identification of an unprecedented function of SlnM, homologous to O‐methyltransferases, by correlating its activity with the formation of the Δ18,19 double bond and bis(spiroacetal). Detailed in vivo and in vitro investigations revealed that SlnM, using positively charged S‐adenosylmethionine (SAM) or sinefungin as the cofactor, catalyzed the spirocyclization‐coupled dehydration of C19 in a highly atypical fashion to yield salinomycin. PMID:26096919

  2. A Facile Method to Prepare Double-Layer Isoporous Hollow Fiber Membrane by In Situ Hydrogen Bond Formation in the Spinning Line.

    PubMed

    Noor, Nazia; Koll, Joachim; Radjabian, Maryam; Abetz, Clarissa; Abetz, Volker

    2016-03-01

    A double-layer hollow fiber is fabricated where an isoporous surface of polystyrene-block-poly(4-vinylpyridine) is fixed on a support layer by co-extrusion. Due to the sulfonation of the support layer material, delamination of the two layers is suppressed without increasing the number of subsequent processing steps for isoporous composite membrane formation. Electron microscope-energy-dispersive X-ray spectroscopy images unveil the existence of a high sulfur concentration in the interfacial region by which in-process H-bond formation between the layers is evidenced. For the very first time, our study reports a facile method to fabricate a sturdy isoporous double-layer hollow fiber. PMID:26685710

  3. Role of the Proximal Cysteine Hydrogen Bonding Interaction in Cytochrome P450 2B4 Studied by Cryoreduction, Electron Paramagnetic Resonance, and Electron-Nuclear Double Resonance Spectroscopy.

    PubMed

    Davydov, Roman; Im, Sangchoul; Shanmugam, Muralidharan; Gunderson, William A; Pearl, Naw May; Hoffman, Brian M; Waskell, Lucy

    2016-02-16

    Crystallographic studies have shown that the F429H mutation of cytochrome P450 2B4 introduces an H-bond between His429 and the proximal thiolate ligand, Cys436, without altering the protein fold but sharply decreases the enzymatic activity and stabilizes the oxyferrous P450 2B4 complex. To characterize the influence of this hydrogen bond on the states of the catalytic cycle, we have used radiolytic cryoreduction combined with electron paramagnetic resonance (EPR) and (electron-nuclear double resonance (ENDOR) spectroscopy to study and compare their characteristics for wild-type (WT) P450 2B4 and the F429H mutant. (i) The addition of an H-bond to the axial Cys436 thiolate significantly changes the EPR signals of both low-spin and high-spin heme-iron(III) and the hyperfine couplings of the heme-pyrrole (14)N but has relatively little effect on the (1)H ENDOR spectra of the water ligand in the six-coordinate low-spin ferriheme state. These changes indicate that the H-bond introduced between His and the proximal cysteine decreases the extent of S → Fe electron donation and weakens the Fe(III)-S bond. (ii) The added H-bond changes the primary product of cryoreduction of the Fe(II) enzyme, which is trapped in the conformation of the parent Fe(II) state. In the wild-type enzyme, the added electron localizes on the porphyrin, generating an S = (3)/2 state with the anion radical exchange-coupled to the Fe(II). In the mutant, it localizes on the iron, generating an S = (1)/2 Fe(I) state. (iii) The additional H-bond has little effect on g values and (1)H-(14)N hyperfine couplings of the cryogenerated, ferric hydroperoxo intermediate but noticeably slows its decay during cryoannealing. (iv) In both the WT and the mutant enzyme, this decay shows a significant solvent kinetic isotope effect, indicating that the decay reflects a proton-assisted conversion to Compound I (Cpd I). (v) We confirm that Cpd I formed during the annealing of the cryogenerated hydroperoxy intermediate

  4. Thieno[3,4-b]pyrazine as an Electron Deficient π-Bridge in D-A-π-A DSCs.

    PubMed

    Liyanage, Nalaka P; Yella, Aswani; Nazeeruddin, Mohammad; Grätzel, Michael; Delcamp, Jared H

    2016-03-01

    Thieno[3,4-b]pyrazine (TPz) is examined as an electron deficient π-bridge enabling near-infrared (NIR) spectral access in dye-sensitized solar cells (DSCs). Seven dissymmetric dyes for DSCs were synthesized (NL2-NL8) with TPz as the π-bridge utilizing palladium catalyzed C-H activation methodology. C-H bond cross-coupling was uniquely effective among the cross-couplings and electrophilic aromatic substitution reactions analyzed in monofunctionalizing the TPz building block. The TPz-based NL2-NL8 dyes examine the effects of various donors, π-spacers, and acceptors within the donor-π bridge-acceptor (D-π-A) dye design. Proaromatic TPz stabilizes the excited-state oxidation potential (E(s+/s*)) of the dyes by maintaining aromaticity upon excitation of the dye molecule. This leads to concise conjugated systems capable of accessing the NIR region. Through judicious structural modifications, dye band gaps were reduced to 1.48 eV, and power conversion efficiencies (PCEs) reached 7.1% in this first generation TPz-dye series. PMID:26866909

  5. Determination of the bond-angle distribution in vitreous B{sub 2}O{sub 3} by {sup 11}B double rotation (DOR) NMR spectroscopy

    SciTech Connect

    Hung, I.; Howes, A.P.; Parkinson, B.G.; Anupold, T.; Samoson, A.; Brown, S.P.; Harrison, P.F.; Holland, D.; Dupree, R.

    2009-09-15

    The B-O-B bond angle distributions for both ring and non-ring boron sites in vitreous B{sub 2}O{sub 3} have been determined by {sup 11}B double rotation (DOR) NMR and multiple-quantum (MQ) DOR NMR. The [B{sub 3}O{sub 6}] boroxol rings are observed to have a mean internal B-O-B angle of 120.0+-0.7 deg. with a small standard deviation, sigma{sub R}=3.2+-0.4 deg., indicating that the rings are near-perfect planar, hexagonal structures. The rings are linked predominantly by non-ring [BO{sub 3}] units, which share oxygens with the boroxol ring, with a mean B{sub ring}-O-B{sub non-ring} angle of 135.1+-0.6 deg. and sigma{sub NR}=6.7+-0.4 deg. In addition, the fraction of boron atoms, f, which reside in the boroxol rings has been measured for this sample as f=0.73+-0.01. - Graphical abstract: Connectivities and B-O-B bond angle distributions of ring and non-ring boron atoms in v-B{sub 2}O{sub 3} have been determined by {sup 11}B double rotation (DOR) NMR, multiple-quantum (MQ) DOR NMR and spin-diffusion DOR. Near-perfect planar, hexagonal [B{sub 3}O{sub 6}] boroxol rings are shown to be present. Display Omitted

  6. Simple but Stronger UO, Double but Weaker UNMe Bonds: The Tale Told by Cp2UO and Cp2UNR

    SciTech Connect

    LPCNO, CNRS-UPS-INSA, INSA Toulouse; Institut Charles Gerhardt, CNRS, Universite Montpellier; Laboratoire de Chimie et Physique Quantiques, CNRS, IRSAMC, Universite Paul Sabatier; Andersen, Richard; Barros, Noemi; Maynau, Daniel; Maron, Laurent; Eisenstein, Odile; Zi, Guofu; Andersen, Richard

    2007-06-27

    The free energies of reaction and the activation energies are calculated, with DFT (B3PW91) and small RECP (relativistic core potential) for uranium, for the reaction of Cp2UNMe and Cp2UO with MeCCMe and H3Si-Cl that yields the corresponding addition products. CAS(2,7) and DFT calculations on Cp2UO and Cp2UNMe give similar results, which validates the use of DFT calculations in these cases. The calculated results mirror the experimental reaction of [1,2,4-(CMe3)3C5H2]2UNMe with dimethylacetylene and [1,2,4-(CMe3)3C5H2]2UO with Me3SiCl. The net reactions are controlled by the change in free energy between the products and reactants, not by the activation energies, and therefore by the nature of the UO and UNMe bonds in the initial and final states. A NBO analysis indicates that the U-O interaction in Cp2UO is composed of a single U-O bond with three lone pairs of electrons localized on oxygen, leading to a polarized U-O fragment. In contrast, the U-NMe interaction in Cp2UNMe is composed of a and component and a lone pairof electrons localized on the nitrogen, resulting in a less polarized UNMe fragment, in accord with the lower electronegativity of NMe relative to O. The strongly polarized U(+)-O(-) bond is calculated to be about 70 kcal mol-1 stronger than the less polarized U=NMe bond.

  7. Controlling pore assembly of staphylococcal gamma-haemolysin by low temperature and by disulphide bond formation in double-cysteine LukF mutants.

    PubMed

    Nguyen, Vananh T; Higuchi, Hideo; Kamio, Yoshiyuki

    2002-09-01

    Staphylococcal LukF and Hlg2 are water-soluble monomers of gamma-haemolysin that assemble into oligomeric pores on the erythrocyte membranes. Here, we have created double-cysteine LukF mutants, in which single disulphide bonds connect either the prestem domain and the cap domain (V12C-T136C, Cap-Stem), or two beta-strands within the prestem domain (T117C-T136C, Stem-Stem) to control pore assembly of gamma-haemolysin at intermediate stages. The disulphide-trapped mutants were inactive in erythrocyte lysis, but gained full haemolytic activity if the disulphide bonds were reduced. The disulphide bonds blocked neither the membrane binding ability nor the intermediate prepore oligomerization, but efficiently inhibited the transition from prepores to pores. The prepores of Cap-Stem were dissociated into monomers in 1% SDS. In contrast, the prepores of Stem-Stem were stable in SDS and had ring-shaped structures similar to those of wild-type LukF, as observed by transmission electron microscopy. The transition of both mutants from prepores to pores could even be achieved by reducing disulphide bonds at low temperature (2 degrees C), whereas prepore oligomerization was effectively inhibited by low temperature. Finally, real-time transition of Stem-Stem from prepores to pores on ghost cells, visualized using a Ca2+-sensitive fluorescent indicator (Rhod2), was shown by the sequential appearance of fluorescence spots, indicating pore-opening events. Taken together, these data indicate that the prepores are legitimate intermediates during gamma-haemolysin pore assembly, and that conformational changes around residues 117 and 136 of the prestem domain are essential for pore formation, but not for membrane binding or prepore oligomerization. We propose a mechanism for gamma-haemolysin pore assembly based on the demonstrated intermediates. PMID:12354220

  8. "Conformational lock"via unusual intramolecular C-FO[double bond, length as m-dash]C and C-HCl-C parallel dipoles observed in in situ cryocrystallized liquids.

    PubMed

    Dey, Dhananjay; Bhandary, Subhrajyoti; Sirohiwal, Abhishek; Hathwar, Venkatesha R; Chopra, Deepak

    2016-06-01

    We report an unusual intramolecular C-FO[double bond, length as m-dash]C and C-HCl-C parallel dipole-dipole alignment which "locks" the molecular conformation of cryocrystallized liquids towards planarity where the diatropic ring current establishes the existence of aromaticity in the five-membered ring associated with FO contact. Topological analysis establishes the bonding interaction between [F, O] and [H, Cl]. PMID:27149236

  9. Efficient second harmonic generation of double-end diffusion-bonded Nd:YVO4 self-Raman laser producing 7.9 W yellow light.

    PubMed

    Zhu, Haiyong; Duan, Yanmin; Zhang, Ge; Huang, Chenghui; Wei, Yong; Shen, Hongyuan; Zheng, Yiqun; Huang, Lingxiong; Chen, Zhenqiang

    2009-11-23

    A high power and efficient 588 nm yellow light is demonstrated through intracavity frequency doubling of an acousto-optic Q-switched self-frequency Raman laser. A 30-mm-length double-end diffusion-bonded Nd:YVO(4) crystal was utilized for efficient self-Raman laser operation by reducing the thermal effects and increasing the interaction length for the stimulated Raman scattering. A 15-mm-length LBO with non-critical phase matching (theta = 90 degrees, phi = 0 degrees) cut was adopted for efficient second-harmonic generation. The focus position of incident pump light and both the repetition rate and the duty cycle of the Q-switch have been optimized. At a repetition rate of 110 kHz and a duty cycle of 5%, the average power of 588 nm light is up to 7.93 W while the incident pump power is 26.5 W, corresponding to an overall diode-yellow conversion efficiency of 30% and a slope efficiency of 43%. PMID:19997395

  10. Anion Transport with Chalcogen Bonds.

    PubMed

    Benz, Sebastian; Macchione, Mariano; Verolet, Quentin; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2016-07-27

    In this report, we introduce synthetic anion transporters that operate with chalcogen bonds. Electron-deficient dithieno[3,2-b;2',3'-d]thiophenes (DTTs) are identified as ideal to bind anions in the focal point of the σ holes on the cofacial endocyclic sulfur atoms. Anion binding in solution and anion transport across lipid bilayers are found to increase with the depth of the σ holes of the DTT anionophores. These results introduce DTTs and related architectures as a privileged motif to engineer chalcogen bonds into functional systems, complementary in scope to classics such as 2,2'-bipyrroles or 2,2'-bipyridines that operate with hydrogen bonds and lone pairs, respectively. PMID:27433964

  11. Photochemical reactions of electron-deficient olefins with N,N,N‧,N‧-tetramethylbenzidine via photoinduced electron-transfer

    NASA Astrophysics Data System (ADS)

    Pan, Yang; Zhao, Junshu; Ji, Yuanyuan; Yan, Lei; Yu, Shuqin

    2006-01-01

    Photoinduced electron transfer reactions of several electron-deficient olefins with N, N, N', N'-tetramethylbenzidine (TMB) in acetonitrile solution have been studied by using laser flash photolysis technique and steady-state fluorescence quenching method. Laser pulse excitation of TMB yields 3TMB* after rapid intersystem crossing from 1TMB*. The triplet which located at 480 nm is found to undergo fast quenching with the electron acceptors fumaronitrile (FN), dimethyl fumarate (DMF), diethyl fumarate (DEF), cinnamonitrile (CN), α-acetoxyacrylonitrile (AAN), crotononitrile (CrN) and 3-methoxyacrylonitrile (MAN). Substituents binding to olefin molecule own different electron-donating/withdrawing powers, which determine the electron-deficient property (π-cloud density) of olefin molecule as well as control the electron transfer rate constant directly. The detection of ion radical intermediates in the photolysis reactions confirms the proposed electron transfer mechanism, as expected from thermodynamics. The quenching rate constants of triplet TMB by these olefins have been determined at 510 nm to avoid the disturbance of formed TMB cation radical around 475 nm. All the kqT values approach or reach to the diffusion-controlled limit. In addition, fluorescence quenching rate constants kqS have been also obtained by calculating with Stern-Volmer equation. A correlation between experimental electron transfer rate constants and free energy changes has been explained by Marcus theory of adiabatic outer-sphere electron transfer. Disharmonic kq values for CN and CrN in endergonic region may be the disturbance of exciplexs formation.

  12. Surface Oxidation under Ambient Air—Not Only a Fast and Economical Method to Identify Double Bond Positions in Unsaturated Lipids But Also a Reminder of Proper Lipid Processing

    PubMed Central

    2015-01-01

    A simple, fast approach elucidated carbon–carbon double bond positions in unsaturated lipids. Lipids were deposited onto various surfaces and the products from their oxidation in ambient air were observed by electrospray ionization (ESI) mass spectrometry (MS). The most common oxidative products, aldehydes, were detected as transformations at the cleaved double bond positions. Ozonides and carboxylic acids were generated in certain lipids. Investigations of the conditions controlling the appearance of these products indicated that the surface oxidation depends on light and ambient air. Since the lipid oxidation was slower in a high concentration of ozone, singlet oxygen appeared to be a parallel oxidant for unsaturated lipids. The 3-hydroxyl group in the sphingoid base of sulfatides offered some protection from oxidation for the Δ4,5-double bond, slowing its oxidation rate relative to that of the isolated double bond in the N-linked fatty acyl chain. Direct sampling by thin-layer chromatography (TLC)-ESI-MS provides a powerful approach to elucidate detailed structural information on biological samples. Co-localization of the starting lipids and their oxidation products after TLC separation allowed assignment of the native unsaturation sites. Phosphatidylserine and N,N-dimethyl phosphatidylethanolamine isomers in a bovine brain total lipid extract were distinguished on the basis of their oxidation products. Meanwhile, the findings reported herein reveal a potential pitfall in the assignment of structures to lipids extracted from TLC plates because of artifactual oxidation after the plate development. PMID:24832382

  13. Phosphate-intercalated Ca-Fe-layered double hydroxides: Crystal structure, bonding character, and release kinetics of phosphate

    NASA Astrophysics Data System (ADS)

    Woo, Myong A.; Woo Kim, Tae; Paek, Mi-Jeong; Ha, Hyung-Wook; Choy, Jin-Ho; Hwang, Seong-Ju

    2011-01-01

    The nitrate-form of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca-Fe-LDH-NO 3- compound and its H 2PO 4--intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO 42- caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca-Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO 42- and H 2PO 4-. Under acidic conditions, phosphate ions were slowly released from the Ca-Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca-Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.

  14. Cationic palladium(ii)-catalyzed dehydrative nucleophilic substitutions of benzhydryl alcohols with electron-deficient benzenethiols in water.

    PubMed

    Hikawa, Hidemasa; Machino, Yumo; Toyomoto, Mariko; Kikkawa, Shoko; Azumaya, Isao

    2016-08-01

    An efficient direct nucleophilic substitution of benzhydryl alcohols with electron-deficient benzenethiols using cationic Pd(ii) catalysts as Lewis acids in water is reported. Atom economical and environmentally benign protocols afford S-benzylated products in moderate to excellent yields. Commercially available Pd(MeCN)4(OTf)2, PdCl2(MeCN)2, and Na2PdCl4 are highly efficient catalysts. Notably, this simple protocol can be achieved without any other additives such as acids, bases, or external ligands. A Hammett study on the rate constants of S-benzylation by using various substituted benzhydryl alcohols yielded negative ρ values, suggesting that there is a build-up of positive charge in the transition state. PMID:27363665

  15. Stabilization of gamma-irradiated poly(vinyl chloride) by epoxy compounds. III. Conjugated double bonds and degree of unsaturation in gamma-irradiated PVC-stabilizer mixtures

    SciTech Connect

    Lerke, G.; Lerke, I.; Szymanski, W.

    1983-01-01

    The concentration of conjugated polyene sequences was studied in ..gamma..-irradiated PVC with 4% admixture of four epoxy stabilizers: diglycidyl ether of 2,2-bis(4-hydroxy-3-methylphenyl)propane (I), styrene oxide (1,2-epoxy ethyl benzene) (IV), epoxidized ricinus oil (VI), and epoxidized soybean oil (Drapex 6.8) (VII). As in the former investigations (Papers I and II), the process of the formation of the polyenes occurs in two stages. The concentration of polyene sequences with n double bonds, H/sub n/ the total amount of polyene sequences, ..sigma..H/sub n/, the average length of the polyene sequence, n, and the extents of reaction x and p, were computed. The stabilizing effect of all compounds used agrees with the increasing content of epoxy groups. The addition of stabilizers diminishes the value of n. The decrease of the fraction of long sequences and the increase of short ones occurs. Apart from the binding of evolved HCl, the protective effect towards the macromolecules of PVC consists mainly in the inhibition of growth of chain dehydrochlorination by the epoxy groups.

  16. Tomato carotenoid cleavage dioxygenases 1A and 1B: Relaxed double bond specificity leads to a plenitude of dialdehydes, mono-apocarotenoids and isoprenoid volatiles

    PubMed Central

    Ilg, Andrea; Bruno, Mark; Beyer, Peter; Al-Babili, Salim

    2014-01-01

    The biosynthetic processes leading to many of the isoprenoid volatiles released by tomato fruits are still unknown, though previous reports suggested a clear correlation with the carotenoids contained within the fruit. In this study, we investigated the activity of the tomato (Solanum lycopersicum) carotenoid cleavage dioxygenase (SlCCD1B), which is highly expressed in fruits, and of its homolog SlCCD1A. Using in vitro assays performed with purified recombinant enzymes and by analyzing products formed by the two enzymes in carotene-accumulating Escherichia coli strains, we demonstrate that SlCCD1A and, to a larger extent, SlCCD1B, have a very relaxed specificity for both substrate and cleavage site, mediating the oxidative cleavage of cis- and all-trans-carotenoids as well as of different apocarotenoids at many more double bonds than previously reported. This activity gives rise to a plenitude of volatiles, mono-apocarotenoids and dialdehyde products, including cis-pseudoionone, neral, geranial, and farnesylacetone. Our results provide a direct evidence for a carotenoid origin of these compounds and point to CCD1s as the enzymes catalyzing the formation of the vast majority of tomato isoprenoid volatiles, many of which are aroma constituents. PMID:25057464

  17. Cholesterol induces surface localization of polyphenols in model membranes thus enhancing vesicle stability against lysozyme, but reduces protection of distant double bonds from reactive-oxygen species.

    PubMed

    de Athayde Moncorvo Collado, Alejandro; Dupuy, Fernando G; Morero, Roberto D; Minahk, Carlos

    2016-07-01

    The main scope of the present study was to analyze the membrane interaction of members of different classes of polyphenols, i.e. resveratrol, naringenin, epigallocatechin gallate and enterodiol, in model systems of different compositions and phase states. In addition, the possible association between membrane affinity and membrane protection against both lipid oxidation and bilayer-disruptive compounds was studied. Gibbs monolayer experiments indicated that even though polyphenols showed poor surface activity, it readily interacted with lipid films. Actually, a preferential interaction with expanded monolayers was observed, while condensed and cholesterol-containing monolayers decreased the affinity of these phenolic compounds. On the other hand, fluorescence anisotropy studies showed that polyphenols were able to modulate membrane order degree, but again this effect was dependent on the cholesterol concentration and membrane phase state. In fact, cholesterol induced a surface rather than deep into the hydrophobic core localization of phenolic compounds in the membranes. In general, the polyphenolic molecules tested had a better antioxidant activity when they were allowed to get inserted into the bilayers, i.e. in cholesterol-free membranes. On the other hand, a membrane-protective effect against bilayer permeabilizing activity of lysozyme, particularly in the presence of cholesterol, could be assessed. It can be hypothesized that phenolic compounds may protect membrane integrity by loosely covering the surface of lipid vesicles, once cholesterol push them off from the membrane hydrophobic core. However, this cholesterol-driven distribution may lead to a reduced antioxidant activity of linoleic acid double bonds. PMID:27063609

  18. Junk-Bond Colleges.

    ERIC Educational Resources Information Center

    Van Der Werf, Martin

    2003-01-01

    Describes how a long-predicted decline in the fortunes of small private colleges is beginning to show up in the bond market, as the number of colleges now rated in the junk category has nearly doubled. (EV)

  19. Construction of an all-carbon quaternary stereocenter by organocatalytic enantioselective α-functionalization of α-substituted β-ketocarbonyls with electron deficient vinylarenes.

    PubMed

    Liu, Shizhou; Tong, Mengchao; Yu, Yang; Xie, Hexin; Li, Hao; Wang, Wei

    2015-06-30

    A chiral amine catalyzed enantioselective α-functionalization of α-substituted β-ketocarbonyls with electron-deficient vinylarenes has been developed to construct the dicarbonyl products with the formation of a chiral all-carbon quaternary stereocenter. The products can be used for the efficient synthesis of useful but challenging chiral quaternary centered pyrazolones. PMID:26077286

  20. Catalytic aziridination of electron-deficient olefins with an N-chloro-N-sodio carbamate and application of this novel method to asymmetric synthesis.

    PubMed

    Minakata, Satoshi; Murakami, Yuta; Tsuruoka, Ryoji; Kitanaka, Shinsuke; Komatsu, Mitsuo

    2008-12-21

    A new method for the aziridination of electron-deficient olefins using an N-chloro-N-sodio carbamate is described; the reaction was promoted by phase-transfer catalysis (solid-liquid) and afforded aziridines from alpha,beta-unsaturated ketones, esters, sulfones and amides. PMID:19048156

  1. Rapid synthesis of an electron-deficient t-BuPHOX ligand: cross-coupling of aryl bromides with secondary phosphine oxides.

    PubMed

    McDougal, Nolan T; Streuff, Jan; Mukherjee, Herschel; Virgil, Scott C; Stoltz, Brian M

    2010-10-20

    Herein an efficient and direct copper-catalyzed coupling of oxazoline-containing aryl bromides with electron-deficient secondary phosphine oxides is reported. The resulting tertiary phosphine oxides can be reduced to prepare a range of PHOX ligands. The presented strategy is a useful alternative to known methods for constructing PHOX derivatives. PMID:21076623

  2. A double-leg donor-acceptor molecular elevator: new insight into controlling the distance of two platforms.

    PubMed

    Zhang, Zhi-Jun; Han, Min; Zhang, Heng-Yi; Liu, Yu

    2013-04-01

    A double-leg elevator with an electron-rich anthracene moiety at the platformlike component and an electron-deficient naphthalenediimide unit in the middle of a double-leg riglike component was prepared through "click chemistry", in which the reversible elevator movement between different levels could be controlled upon the addition of base and acid. PMID:23534551

  3. Chlorine atom-initiated low-temperature oxidation of prenol and isoprenol: The effect of C=C double bonds on the peroxy radical chemistry in alcohol oxidation

    DOE PAGESBeta

    Welz, Oliver; Savee, John D.; Osborn, David L.; Taatjes, Craig A.

    2014-07-04

    The chlorine atom-initiated oxidation of two unsaturated primary C5 alcohols, prenol (3-methyl-2-buten-1-ol, (CH3)2CCHCH2OH) and isoprenol (3-methyl-3-buten-1-ol, CH2C(CH3)CH2CH2OH), is studied at 550 K and low pressure (8 Torr). The time- and isomer-resolved formation of products is probed with multiplexed photoionization mass spectrometry (MPIMS) using tunable vacuum ultraviolet ionizing synchrotron radiation. The peroxy radical chemistry of the unsaturated alcohols appears much less rich than that of saturated C4 and C5 alcohols. The main products observed are the corresponding unsaturated aldehydes – prenal (3-methyl-2-butenal) from prenol oxidation and isoprenal (3-methyl-3-butenal) from isoprenol oxidation. No significant products arising from QOOH chemistry are observed. Thesemore » results can be qualitatively explained by the formation of resonance stabilized allylic radicals via H-abstraction in the Cl + prenol and Cl + isoprenol initiation reactions. The loss of resonance stabilization upon O2 addition causes the energies of the intermediate wells, saddle points, and products to increase relative to the energy of the initial radicals and O2. These energetic shifts make most product channels observed in the peroxy radical chemistry of saturated alcohols inaccessible for these unsaturated alcohols. The experimental findings are underpinned by quantum-chemical calculations for stationary points on the potential energy surfaces for the reactions of the initial radicals with O2. Under our conditions, the dominant channels in prenol and isoprenol oxidation are the chain-terminating HO2-forming channels arising from radicals, in which the unpaired electron and the –OH group are on the same carbon atom, with stable prenal and isoprenal co-products, respectively. These results suggest that the presence of C=C double bonds in alcohols will reduce low-temperature reactivity during autoignition.« less

  4. Design and synthesis of novel derivatives of all-trans retinoic acid demonstrate the combined importance of acid moiety and conjugated double bonds in its binding to PML–RAR-α oncogene in acute promyelocytic leukemia

    PubMed Central

    Schinke, Carolina; Goel, Swati; Bhagat, Tushar D.; Zhou, Li; Mo, Yongkai; Gallagher, Robert; Kabalka, George W.; Platanias, Leonidas C.; Verma, Amit; Das, Bhaskar

    2014-01-01

    The binding of all-trans retinoic acid (ATRA) to retinoid receptor-α (RAR-α) relieves transcriptional repression induced by the promyelocytic leukemia–retinoic acid receptor (PML–RAR) oncoprotein. The ATRA molecule contains a cyclohexenyl ring, a polyene chain containing conjugated double alkene bonds, and a terminal carboxyl group. To determine the contributions of these structural components of ATRA to its clinical efficacy, we synthesized three novel retinoids. These consisted of either a modified conjugated alkene backbone with an intact acid moiety (13a) or a modified conjugated alkene backbone and conversion of the acid group to either an ester (13b) or an aromatic amide (13c). Reporter assays demonstrated that compound 13a successfully relieved transcriptional repression by RAR-α, while 13b and 13c could not, demonstrating the critical role of the acid moiety in this binding. However, only ATRA was able to significantly inhibit the proliferation of APL cells while 13a, 13b, or 13c was not. Furthermore, only 13a led to partial non-significant differentiation of NB4 cells, demonstrating the importance of C9–C10 double bonds in differentiation induced CD11 expression. Our results demonstrate that both the acid moiety and conjugated double bonds present in the ATRA molecule are important for its biological activity in APL and have important implications for the design of future novel retinoids. PMID:20536349

  5. On the Relationship between the Enthalpy of Formation of Carbenes upon Cleavage of the Double Bond in Fluoroolefins and the Electron Density on the pi Bond: An Ab Initio Study

    SciTech Connect

    Borisov, Yurii A.; Garrett, Bruce C.; Kobanovskii, Y. A.; Bilera, I. V.; Buravtsev, N. N.

    2003-08-07

    In this study, we established a correlation between the enthalpy of cleavage of the C=C bond in fluorine-substituted olefins giving rise to two carbenes in the electronic ground state and the distribution of the electron density on this bond.

  6. Possible interstellar formation of glycine through a concerted mechanism: a computational study on the reaction of CH2[double bond, length as m-dash]NH, CO2 and H2.

    PubMed

    Nhlabatsi, Zanele P; Bhasi, Priya; Sitha, Sanyasi

    2016-07-27

    Glycine being the simplest amino acid and also having significant astrobiological implications, has meant that intensive investigations have been carried out in the past, starting from its detection in the interstellar medium (ISM) to analysis of meteorites and cometary samples and laboratory synthesis, as well as computational studies on the possible reaction paths. In this present work quantum chemical calculations have been performed to investigate the possible interstellar formation of glycine via two different paths; (1) in a two-step process via a dihydroxy carbene intermediate and (2) through a one-step concerted mechanism, starting from reactants like CH2[double bond, length as m-dash]NH, CO, CO2, H2O and H2. For the two reactions representing the carbene route, it was observed that the formation of dihydroxy carbene from either CO + H2O or CO2 + H2 is highly endothermic with large barrier heights, whereas the subsequent step of interaction of this carbene with CH2[double bond, length as m-dash]NH to give glycine is exothermic and the barrier is below the reactants. Based on this observation it is suggested that the formation of glycine via the carbene route is a least favourable or even unfavourable path. On the other hand, the two reactions CH2[double bond, length as m-dash]NH + CO + H2O and CH2[double bond, length as m-dash]NH + CO2 + H2 representing the concerted paths were found to be favourable in leading to the formation of glycine. After an extensive study on the first concerted reaction in our previous work (Phys. Chem. Chem. Phys., 2016, 18, 375-381), in this work a detailed investigation has been carried out for the second concerted reaction, CH2[double bond, length as m-dash]NH + CO2 + H2, which can possibly lead to the interstellar formation of glycine. It was observed that this reaction proceeds through a large barrier and at the same time the transition state shows prominent hydrogen dynamics, indicating a tunnelling possibility for this

  7. Copper(I)-catalyzed alkylation of polyfluoroarenes through Direct C-H bond functionalization.

    PubMed

    Xu, Shuai; Wu, Guojiao; Ye, Fei; Wang, Xi; Li, Huan; Zhao, Xia; Zhang, Yan; Wang, Jianbo

    2015-04-01

    The copper(I)-catalyzed alkylation of electron-deficient polyfluoroarenes with N-tosylhydrazones and diazo compounds has been developed. This reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of C(sp(2) )-C(sp(3) ) bonds with polyfluoroarenes through direct C-H bond functionalization. Mechanistically, copper(I) carbene formation and subsequent migratory insertion are proposed as the key steps in the reaction pathway. PMID:25690761

  8. Chlorine atom-initiated low-temperature oxidation of prenol and isoprenol: The effect of C=C double bonds on the peroxy radical chemistry in alcohol oxidation

    SciTech Connect

    Welz, Oliver; Savee, John D.; Osborn, David L.; Taatjes, Craig A.

    2014-07-04

    The chlorine atom-initiated oxidation of two unsaturated primary C5 alcohols, prenol (3-methyl-2-buten-1-ol, (CH3)2CCHCH2OH) and isoprenol (3-methyl-3-buten-1-ol, CH2C(CH3)CH2CH2OH), is studied at 550 K and low pressure (8 Torr). The time- and isomer-resolved formation of products is probed with multiplexed photoionization mass spectrometry (MPIMS) using tunable vacuum ultraviolet ionizing synchrotron radiation. The peroxy radical chemistry of the unsaturated alcohols appears much less rich than that of saturated C4 and C5 alcohols. The main products observed are the corresponding unsaturated aldehydes – prenal (3-methyl-2-butenal) from prenol oxidation and isoprenal (3-methyl-3-butenal) from isoprenol oxidation. No significant products arising from QOOH chemistry are observed. These results can be qualitatively explained by the formation of resonance stabilized allylic radicals via H-abstraction in the Cl + prenol and Cl + isoprenol initiation reactions. The loss of resonance stabilization upon O2 addition causes the energies of the intermediate wells, saddle points, and products to increase relative to the energy of the initial radicals and O2. These energetic shifts make most product channels observed in the peroxy radical chemistry of saturated alcohols inaccessible for these unsaturated alcohols. The experimental findings are underpinned by quantum-chemical calculations for stationary points on the potential energy surfaces for the reactions of the initial radicals with O2. Under our conditions, the dominant channels in prenol and isoprenol oxidation are the chain-terminating HO2-forming channels arising from radicals, in which the unpaired electron and the –OH group are on the same carbon atom, with stable prenal and isoprenal co-products, respectively. These results suggest that the presence of C=C double bonds in alcohols will reduce

  9. Influence of spacer moiety and length of end chain for the phase stability in complementary, double hydrogen bonded liquid crystals, MA:nOBAs

    NASA Astrophysics Data System (ADS)

    Ashok Kumar, A. V. N.; Chalapathi, P. V.; Srinivasulu, M.; Muniprasad, M.; Potukuchi, D. M.

    2015-01-01

    Supra molecular liquid crystals formed by the Hydrogen Bonding interaction between a non-mesogenic aliphatic dicarboxylic acid viz., COOHsbnd CH2sbnd COOH (Malonic Acid, MA); and mesogenic aromatic, N-(p-n-alkoxy benzoic)Acids, (i.e., nOBAs) for n = 3, 4, 5, 7, 8, 9, 10, 11 and 12, labeled as nOBA:COOHsbnd [CH2]msbnd COOH:nOBAs, abbreviated as MA:nOBAs are reported. 1H NMR and 13C NMR studies confirm the formation of HBLC complexes. Infrared (IR) studies confirm the complementary, double, alternative type of HB. Polarized Optical Microscopy (POM) and Differential Scanning Calorimetry (DSC) studies infer N, SmC, SmX, SmCRE, SmF, SmG LC phase variance. SmX phase exhibiting finger print texture grows in MA:nOBAs for n = 10, 11 and 12 by the interruption of SmC phase with decreasing temperature. Re-Entrant SmC (SmCRE) grows by the cooling of SmX. I-N, N-C, X-CRE, C-G, CRE-F, F-G and G-Solid transitions exhibit first order nature. C-X is found to be second order nature in n = 10 and 11. C-X in n = 12 and X-CRE and CRE-F transitions are found to be weak first order nature. Influence of lengths of end chain (n) and spacer (m) for the overall LC phase [ΔT]LC; tilted phase [ΔT]Tilt; SmC phase [ΔT]C and SmX phase [ΔT]X stabilities is discussed in the wake of data on other HBLCs with similar molecular structure. Prevalence of SmX phase in MA:nOBAs with m = 1 infers repulsive interaction between the π-electronic cloud of aromatic boards of nOBAs. Model molecule predicts a twisted configuration of π-cloud around the molecular long axis. Finger print texture of SmX validates the model.

  10. Low-valent niobium-mediated double activation of C-F/C-H bonds: fluorene synthesis from o-arylated alpha,alpha,alpha-trifluorotoluene derivatives.

    PubMed

    Fuchibe, Kohei; Akiyama, Takahiko

    2006-02-01

    By the treatment of 0.3 molar amount of NbCl5 and LiAlH4, o-arylated alpha,alpha,alpha-trifluorotoluenes afforded fluorene derivatives in good yields. C-F bonds of the CF3 group and the neighboring ortho C-H bond were doubly activated to give the coupling products. PMID:16448098

  11. Chiral Phosphorus-Olefin Ligands for the Rh(I) -Catalyzed Asymmetric Addition of Aryl Boronic Acids to Electron-Deficient Olefins.

    PubMed

    Chen, Qian; Li, Liang; Zhou, Guangli; Ma, Xiaoli; Zhang, Lu; Guo, Fang; Luo, Yi; Xia, Wujiong

    2016-05-20

    New chiral phosphorus-olefin hybrid ligands derived from the rigid "privileged" l-proline have been conveniently prepared and applied in the rhodium-catalyzed asymmetric arylation of electron-deficient olefins with arylboronic acids at room temperature; this reaction provides the desired products in excellent yields and high enantioselectivities. The origin of observed stereoselectivity has been investigated by density functional theory (DFT) calculations. PMID:27017447

  12. Tuning of the electronic properties of a cyclopentadienylruthenium catalyst to match racemization of electron-rich and electron-deficient alcohols.

    PubMed

    Verho, Oscar; Johnston, Eric V; Karlsson, Erik; Bäckvall, Jan-E

    2011-09-26

    The synthesis of a new series of cyclopentadienylruthenium catalysts with varying electronic properties and their application in racemization of secondary alcohols are described. These racemizations involve two key steps: 1) β-hydride elimination (dehydrogenation) and 2) re-addition of the hydride to the intermediate ketone. The results obtained confirm our previous theory that the electronic properties of the substrate determine which of these two steps is rate determining. For an electron-deficient alcohol the rate-determining step is the β-hydride elimination (dehydrogenation), whereas for an electron-rich alcohol the re-addition of the hydride becomes the rate-determining step. By matching the electronic properties of the catalyst with the electronic properties of the alcohol, we have now shown that a dramatic increase in racemization rate can be obtained. For example, electron-deficient alcohol 15 racemized 30 times faster with electron-deficient catalyst 6 than with the unmodified standard catalyst 4. The application of these protocols will extend the scope of cyclopentadienylruthenium catalysts in racemization and dynamic kinetic resolution. PMID:21882268

  13. A double addition of Ln-H to a carbon-carbon triple bond and competitive oxidation of ytterbium(II) and hydrido centers.

    PubMed

    Basalov, Ivan V; Lyubov, Dmitry M; Fukin, Georgy K; Shavyrin, Andrei S; Trifonov, Alexander A

    2012-04-01

    Addition of two Ln-H bonds of an Yb(II) hydrido complex supported by bulky amidinate ligand to a C≡C bond lead to the formation of 1,2-dianionic bibenzyl fragment. Both Yb(II) and hydrido centers are oxidized under the reaction conditions. The resulting Yb(II)-η(6) -arene interaction is surprisingly robust: the arene cannot be replaced from the metal coordination sphere when treated with Lewis bases. PMID:22374856

  14. Study on the d state of platinum in Pt/SiO sub 2 and Na/Pt/SiO sub 2 catalysts under C double bond C hydrogenation conditions by X-ray absorption near-edge structure spectroscopy

    SciTech Connect

    Yoshitake, Hideaki; Iwasawa, Yasuhiro )

    1991-09-19

    The change in the d-electron density of platinum during D{sub 2} + CH{sub 2}{double bond}CHX reactions on Pt/SiO{sub 2} and Na/Pt/SiO{sub 2} catalysts and its influence on the catalysis were studied by X-ray absorption near-edge structure (XANES) spectroscopy, kinetics and FT-IR. It was demonstrated from the change of the white lines in XANES spectra at Pt L{sub 2} and L{sub 3} edges that CH{sub 2}{double bond}CHX (X = H, CH{sub 3}, COCH{sub 3}, CF{sub 3}, and CN) is adsorbed on the Pt surface and extracts the electrons of the d state. Hence, the deuterogenation rate is reduced as the value of Hammett's {sigma}{sub P} increases. The linear free energy relationship between the reaction rate and {sigma}{sub P} was observed for the deuterogenation of CH{sub 2}{double bond}CHX. The rate of ethene deuterogenation was promoted by Na{sub 2}O addition. The electron density of unoccupied d states of pt under vacuum decreased by Na{sub 2}O addition, indicating the electron donation from Na{sub 2}O addition. The electron density of unoccupied d states of Pt under vacuum decreased by Na{sub 2}O addition, indicating the electron donation from Na{sub 2}O addition. However, most of these additional electrons were observed to move to ethene under reaction conditions. The acceptor of the electrons was suggested by di-{sigma}-ethene by the shift of {upsilon}(C-H). The kinetic parameters are discussed in relation to the change in the d state of Pt as a function of {sigma}{sub P} and Na quantity.

  15. Promoting C–C Bond Coupling of Benzyne and Methyl Ligands in Electron-Deficient (triphos)Pt–CH3+ Complexes

    PubMed Central

    2016-01-01

    In situ generated benzyne reacts at room temperature with (triphos)Pt–CH3+ to form a five-coordinate π-complex (2) that is isolable and stable in solution. Thermolysis of 2 at 60 °C generates (triphos)Pt(o-tolyl)+ (3), which is the product of formal migratory insertion of CH3– onto the coordinated benzyne. The reaction of 2 with the acid Ph2NH2+ yields toluene at room temperature over the course of 8 h, while the same reaction with 3 only proceeds to 40% conversion over 2 days. These data indicate that the protonolysis of 2 does not proceed by CH3 migration onto benzyne to form 3 followed by protodemetalation. Instead, the data suggest either that protonation of 2 is first and is followed by H migration to yield a PtIVPh(Me) dication or that this latter species is generated by direct protonolysis of coordinated benzyne prior to reductive elimination of toluene. PMID:26146438

  16. Utilization of N-X bonds in the synthesis of N-heterocycles.

    PubMed

    Minakata, Satoshi

    2009-08-18

    Nitrogen-containing heterocycles--such as aziridines, pyrrolidines, piperidines, and oxazolines--frequently show up as substructures in natural products. In addition, some of these species show potent biological activities. Therefore, researchers would like to develop practical and convenient methods for constructing these heterocycles. Among the available methods, the transfer of N(1) units to organic molecules, especially olefins, is a versatile method for the synthesis of N-heterocycles. This Account reviews some of our recent work on the synthesis of N-heterocycles using the N-X bond. A nitrogen-halogen bond bearing an electron-withdrawing group on the nitrogen can be converted to a halonium ion. In the presence of C-C double bonds, these species produce three-membered cyclic halonium intermediates, which can be strong electrophiles and can produce stereocontrolled products. N-Halosuccinimides are representative sources of halonium ions, and the nitrogen of succinimide is rarely used in organic synthesis. If the nitrogen could act as a nucleophile, after releasing halonium ions to C-C double bonds, we expect great advances would be possible in the stereoselective functionalization of olefins. We chose N-chloro-N-sodio-p-toluenesulfonamide (chloramine-T, CT), an inexpensive and commercially available reagent, as our desired reactant. In the presence of a catalytic amount of CuCl or I(2) and AgNO(3), we achieved the direct aziridination of olefins with CT. The reaction catalyzed by I(2) could be carried out in water or silica-water as a green process. The reaction of iodoolefins with CT gave pyrrolidine derivatives under extremely mild conditions with complete stereoselectivity. We also extended the utility of the N-chloro-N-metallo reagent, which is often unstable and difficult to work with. Although CT does not react with electron-deficient olefins without a metal catalyst or an additive, we found that N-chloro-N-sodiocarbamates react with electron-deficient

  17. Achieving high performance non-fullerene organic solar cells through tuning the numbers of electron deficient building blocks of molecular acceptors

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Chen, Yusheng; Chen, Shangshang; Dong, Tao; Deng, Wei; Lv, Lei; Yang, Saina; Yan, He; Huang, Hui

    2016-08-01

    Two analogous dimer and tetramer compounds, SF-PDI2 and SF-PDI4, were designed, theoretically calculated, synthesized, and developed as electron acceptors for organic solar cells. The effects of the number of the electron deficient building blocks on the optical absorption, energy levels, charge transport, morphology, crystallinity, and photovoltaic performance of the molecules were investigated. In combination with two different donors, PTB7-Th and PffBT4T-2OD, the results showed that increasing the numbers of PDI building blocks is beneficial to photovoltaic performance and leads to efficiency over 5%.

  18. A unique quinolineboronic acid-based supramolecular structure that relies on double intermolecular B-N bonds for self-assembly in solid state and in solution.

    PubMed

    Zhang, Yanling; Li, Minyong; Chandrasekaran, Sekar; Gao, Xingming; Fang, Xikui; Lee, Hsiau-Wei; Hardcastle, Kenneth; Yang, Jenny; Wang, Binghe

    2007-04-16

    The boronic acid functional group plays very important roles in sugar recognition, catalysis, organic synthesis, and supramolecular assembly. Therefore, understanding the unique properties of this functional group is very important. 8-Quinolineboronic acid (8-QBA) is found to be capable of self-assembling in solid state through a unique intermolecular B-N bond mechanism reinforced by intermolecular boronic anhydride formation, π-π stacking, and hydrogen bond formation. NMR NOE and diffusion studies indicate that intermolecular B-N interaction also exists in solution with 8-QBA. In contrast, a positional isomer of 8-QBA, 5-quinolineboronic acid (5-QBA) showed very different behaviors in crystal packing and in solution and therefore different supramolecular network. Understanding the structural features of this unique 8-QBA assembly could be very helpful for the future design of new sugar sensors, molecular catalysts, and supramolecular assemblies. PMID:18414645

  19. A unique quinolineboronic acid-based supramolecular structure that relies on double intermolecular B-N bonds for self-assembly in solid state and in solution

    PubMed Central

    Zhang, Yanling; Li, Minyong; Chandrasekaran, Sekar; Gao, Xingming; Fang, Xikui; Lee, Hsiau-Wei; Hardcastle, Kenneth; Yang, Jenny; Wang, Binghe

    2007-01-01

    The boronic acid functional group plays very important roles in sugar recognition, catalysis, organic synthesis, and supramolecular assembly. Therefore, understanding the unique properties of this functional group is very important. 8-Quinolineboronic acid (8-QBA) is found to be capable of self-assembling in solid state through a unique intermolecular B-N bond mechanism reinforced by intermolecular boronic anhydride formation, π-π stacking, and hydrogen bond formation. NMR NOE and diffusion studies indicate that intermolecular B-N interaction also exists in solution with 8-QBA. In contrast, a positional isomer of 8-QBA, 5-quinolineboronic acid (5-QBA) showed very different behaviors in crystal packing and in solution and therefore different supramolecular network. Understanding the structural features of this unique 8-QBA assembly could be very helpful for the future design of new sugar sensors, molecular catalysts, and supramolecular assemblies. PMID:18414645

  20. Factors Controlling the Spectroscopic Properties and Supramolecular Chemistry of an Electron Deficient 5,5-Dimethylphlorin Architecture

    PubMed Central

    2015-01-01

    A new 5,5-dimethylphlorin derivative (3H(PhlCF3)) was prepared and studied through a combination of redox, photophysical, and computational experiments. The phlorin macrocycle is significantly distorted from planarity compared to more traditional tetrapyrrole architectures and displays solvatochroism in the soret region of the UV–vis spectrum (∼370–420 nm). DFT calculations indicate that this solvatochromic behavior stems from the polarized nature of the frontier orbital (LUMO+1) that is most heavily involved in these transitions. Compound 3H(PhlCF3) also displays an intriguing supramolecular chemistry with certain anions; this phlorin can cooperatively hydrogen-bond two equivalents of fluoride to form 3H(PhlCF3)·2F– but does not bind larger halides such as Cl– or Br–. Analogous studies revealed that the phlorin can hydrogen-bond with carboxylate anions such as acetate to form 1:1 complexes such as 3H(PhlCF3)·OAc–. These supramolecular assemblies are robust and form even in relatively polar solvents such as MeCN. Hydrogen-bonding of fluoride and acetate anions to the phlorin N–H residues significantly attenuates the redox and photophysical properties of the phlorin. Moreover, The ability to independently vary the size and pKa of a series of carboxylate hydrogen-bond acceptors has allowed us to probe how phlorin–anion association is controlled by the anion’s size and/or basicity. These studies elucidate the physical properties and the electronic effects that shape the supramolecular chemistry displayed by the phlorin platform. PMID:25018789

  1. Factors Controlling the Spectroscopic Properties and Supramolecular Chemistry of an Electron Deficient 5,5- Dimethylphlorin Architecture

    SciTech Connect

    Pistner, Allen; Lutterman, Daniel A; Ghidiu, Michael J.; Walker, Eric; Yapp, Glenn P. A.; Rosenthal, Joel

    2014-01-01

    A new 5,5-dimethylphlorin derivative (3H-(PhlCF3)) was prepared and studied through a combination of redox, photophysical, and computational experiments. The phlorin macrocycle is significantly distorted from planarity compared to more traditional tetrapyrrole architectures and displays solvatochroism in the soret region of the UV vis spectrum ( 370 420 nm). DFT calculations indicate that this solvatochromic behavior stems from the polarized nature of the frontier orbital (LUMO+1) that is most heavily involved in these transitions. Compound 3H(PhlCF3) also displays an intriguing supramolecular chemistry with certain anions; this phlorin can cooperatively hydrogen-bond two equivalents of fluoride to form 3H(PhlCF3) 2F but does not bind larger halides such as Cl or Br . Analogous studies revealed that the phlorin can hydrogen-bond with carboxylate anions such as acetate to form 1:1 complexes such as 3H(PhlCF3) OAc . These supramolecular assemblies are robust and form even in relatively polar solvents such as MeCN. Hydrogen-bonding of fluoride and acetate anions to the phlorin N H residues significantly attenuates the redox and photophysical properties of the phlorin. Moreover, The ability to independently vary the size and pKa of a series of carboxylate hydrogen-bond acceptors has allowed us to probe how phlorin anion association is controlled by the anion s size and/or basicity. These studies elucidate the physical properties and the electronic effects that shape the supramolecular chemistry displayed by the phlorin platform.

  2. Hypovalency--a kinetic-energy density description of a 4c-2e bond.

    PubMed

    Jacobsen, Heiko

    2009-06-01

    A bond descriptor based on the kinetic energy density, the localized-orbital locator (LOL), is used to characterize the nature of the chemical bond in electron deficient multi-center bonds. The boranes B(2)H(6), B(4)H(4), B(4)H(10), [B(6)H(6)](2-), and [B(6)H(7)](-) serve as prototypical examples of hypovalent 3c-2e and 4c-2e bonding. The kinetic energy density is derived from a set of Kohn-Sham orbitals obtained from pure density functional calculations (PBE/TZVP), and the topology of LOL is analyzed in terms of (3,-3) attractors (Gamma). The B-B-B and B-H-B 3c-2e, and the B-B-H-B 4c-2e bonding situations are defined by their own characteristic LOL profiles. The presence of one attractor in relation to the three or four atoms that are engaged in electron deficient bonding provides sufficient indication of the type of 3c-2e or 4c-2e bond present. For the 4c-2e bond in [B(6)H(7)](-) the LOL analysis is compared to results from an experimental QTAIM study. PMID:19452076

  3. General and facile method for exo-methlyene synthesis via regioselective C-C double-bond formation using a copper-amine catalyst system.

    PubMed

    Nishikata, Takashi; Nakamura, Kimiaki; Itonaga, Kohei; Ishikawa, Shingo

    2014-11-01

    In this study, for distal-selective β-hydride elimination to produce exomethylene compounds with a newly formed Csp(3)-Csp(3) bond between tertiary alkyl halides and α-alkylated styrenes, a combination of a Cu(I) salt and a pyridine-based amine ligand (TPMA) is found to be a very efficient catalyst system. The yields and regioselectivities were high, and the regioselectivity was found to be dependent on the structure of the alkyl halide, with bulky alkyl halides showing the highest distal selectivities. PMID:25315319

  4. Recent Progress in Visible-Light Photoredox-Catalyzed Intermolecular 1,2-Difunctionalization of Double Bonds via an ATRA-Type Mechanism.

    PubMed

    Courant, Thibaut; Masson, Géraldine

    2016-08-19

    Radical difunctionalizations of alkenes constitute an efficient method for the construction of complex organic molecules. This synopsis focuses on visible-light catalysis, a recent and very promising technological refinement of this class of transformations. Examples taken from the literature illustrate the use of a variety of (metallic or nonmetallic) systems, which allow us to leverage the energy of readily available visible-light radiation to efficiently create some of the most commonly looked for types of bonds (C-X, C-O, C-N, and C-C) under mild conditions and starting from unsaturated substrates. PMID:27323289

  5. Halogen bonding in water results in enhanced anion recognition in acyclic and rotaxane hosts.

    PubMed

    Langton, Matthew J; Robinson, Sean W; Marques, Igor; Félix, Vítor; Beer, Paul D

    2014-12-01

    Halogen bonding (XB), the attractive interaction between an electron-deficient halogen atom and a Lewis base, has undergone a dramatic development as an intermolecular force analogous to hydrogen bonding (HB). However, its utilization in the solution phase remains underdeveloped. Furthermore, the design of receptors capable of strong and selective recognition of anions in water remains a significant challenge. Here we demonstrate the superiority of halogen bonding over hydrogen bonding for strong anion binding in water, to the extent that halide recognition by a simple acyclic mono-charged receptor is achievable. Quantification of iodide binding by rotaxane hosts reveals the strong binding by the XB-rotaxane is driven exclusively by favourable enthalpic contributions arising from the halogen-bonding interactions, whereas weaker association with the HB-rotaxanes is entropically driven. These observations demonstrate the unique nature of halogen bonding in water as a strong alternative interaction to the ubiquitous hydrogen bonding in molecular recognition and assembly. PMID:25411880

  6. Colochiroside E, an Unusual Non-holostane Triterpene Sulfated Trioside from the Sea Cucumber Colochirus robustus and Evidence of the Impossibility of a 7(8)-Double Bond Migration in Lanostane Derivatives having an 18(16)-Lactone.

    PubMed

    Silchenko, Alexandra S; Kalinovsky, Anatoly I; Avilov, Sergey A; Andryjaschenko, Pelageya V; Dmitrenok, Pavel S; Yurchenko, Ekaterina A; Dolmatov, Igor Yu; Dautov, Salim Sh; Stonik, Valentin A; Kalinin, Vladimir I

    2016-06-01

    The unusual non-holostane triterpene glycoside, colochiroside E (1) was isolated from the sea cucumber Colochirus robustus (Cucumariidae, Dendrochirotida). The structure of 1 was established by analysis of 1D, 2D NMR and HRESI MS data. Colochiroside E (1) belongs to a rare group of glycosylated 9β-H-lanosta-18(16)-lactones and has an unprecedented sulfated trisaccharide carbohydrate chain consisting of two glucose and one xylose units. In contrast with (9β-H)-7(8)-unsaturated holostane glycosides, the 7(8)-double bond in the having (9β-H)-configuration aglycone of colochiroside E is not capable of migration into the 8(9)- and then into the 9(11)-position on treatment with HCl. The formation of a chlorine derivative of 1 was observed under these conditions. PMID:27534106

  7. N-benzylideneaniline and N-benzylaniline are potent inhibitors of lignostilbene-alpha,beta-dioxygenase, a key enzyme in oxidative cleavage of the central double bond of lignostilbene.

    PubMed

    Han, Sun-Young; Inoue, Hiroki; Terada, Tamami; Kamoda, Shigehiro; Saburi, Yoshimasa; Sekimata, Katsuhiko; Saito, Tamio; Kobayashi, Masatomo; Shinozaki, Kazuo; Yoshida, Shigeo; Asami, Tadao

    2003-06-01

    Lignostilbene-alpha,beta-dioxygenase (LSD, EC 1.13.11.43) is involved in oxidative cleavage of the central double bond of lignostilbene to form the corresponding aldehydes by a mechanism similar to those of 9-cis-epoxycarotenoid dioxygenase and beta-carotene 15,15'-dioxygenase, key enzymes in abscisic acid biosynthesis and vitamin A biosynthesis, respectively. In this study, several N-benzylideneanilines and amine were synthesized and examined for their efficacy as inhibitors of LSD. N-(4-Hydroxybenzylidene)-3-methoxyaniline was found to be a potent inhibitor with IC50 = 0.3 microM and N-(4-hydroxybenzyl)-3-methoxyaniline was also active with IC50 = 10 microM. The information obtained from the structure-activity relationships study here can aid in discovering inhibitors of both abscisic acid and vitamin A biosynthesis. PMID:14506920

  8. The role of π-bonding on the high temperature structure of the double perovskites Ba2CaUO6 and BaSrCaUO6.

    PubMed

    Reynolds, Emily; Thorogood, Gordon J; Avdeev, Maxim; Brand, Helen E A; Gu, Qinfen; Kennedy, Brendan J

    2015-09-28

    The high temperature structural behaviour of the uranium perovskites Ba2CaUO6 and BaSrCaUO6 has been investigated using a combination of synchrotron X-ray and neutron powder diffraction. Ba2CaUO6 undergoes a complex sequence of structures associated with the progressive loss of cooperative octahedral tilting: P21/n → I2/m → I2/m → I4/m → Fm3[combining macron]m. The observation of the intermediate tetragonal structure, I4/m, in this, contrasts with the previously reported rhombohedral R3[combining macron] intermediate formed by the Ba2SrUO6 oxide. The importance of π-bonding in determining the structural sequence is discussed. PMID:26286063

  9. Bonding aerogels with polyurethanes

    SciTech Connect

    Matthews, F.M.; Hoffman, D.M.

    1989-11-01

    Aerogels, porous silica glasses with ultra-fine cell size (30nm), are made by a solution gelation (sol-gel) process. The resulting gel is critical point dried to densities from 0.15--0.60 g/cc. This material is machinable, homogeneous, transparent, coatable and bondable. To bond aerogel an adhesive should have long cure time, no attack on the aerogel structure, and high strength. Several epoxies and urethanes were examined to determine if they satisfied these conditions. Bond strengths above 13 psi were found with double bubble and DP-110 epoxies and XI-208/ODA-1000 and Castall U-2630 urethanes. Hardman Kalex Tough Stuff'' A-85 hardness urethane gave 18 psi bond strength. Hardman A-85, Tuff-Stuff'' was selected for further evaluation because it produced bond strengths comparable to the adherend cohesive strength. 5 refs., 2 figs.

  10. Recycling of MSWI fly ash by means of cementitious double step cold bonding pelletization: Technological assessment for the production of lightweight artificial aggregates.

    PubMed

    Colangelo, Francesco; Messina, Francesco; Cioffi, Raffaele

    2015-12-15

    In this work, an extensive study on the recycling of municipal solid waste incinerator fly ash by means of cold bonding pelletization is presented. The ash comes from an incineration plant equipped with rotary and stoker furnaces, in which municipal, hospital and industrial wastes are treated. Fly ash from waste incineration is classified as hazardous and cannot be utilized or even landfilled without prior treatment. The pelletization process uses cement, lime and coal fly ash as components of the binding systems. This process has been applied to several mixes in which the ash content has been varied from 50% (wt.%) up to a maximum of 70%. An innovative additional pelletization step with only cementitious binder has been performed in order to achieve satisfactory immobilization levels. The obtained lightweight porous aggregates are mostly suitable for recovery in the field of building materials with enhanced sustainability properties. Density, water absorption and crushing strength ranged from 1000 to 1600 kg/m(3), 7 to 16% and 1.3 to 6.2 MPa, respectively, and the second pelletization step increased stabilization efficiency. The feasibility of the process has been analyzed by testing also concrete specimens containing the artificial aggregates, resulting in lightweight concrete of average performance. PMID:26124064

  11. Three-component synthesis of C2F5-substituted pyrazoles from C2F5CH2NH2·HCl, NaNO2 and electron-deficient alkynes

    PubMed Central

    2015-01-01

    Summary A one-pot reaction between C2F5CH2NH2·HCl, NaNO2 and electron-deficient alkynes gives C2F5-substituted pyrazoles in excellent yields. The transformation smoothly proceeds in dichloromethane/water, tolerates the presence of air, and requires no purification of products by column chromatography. Mechanistically, C2F5CH2NH2·HCl and NaNO2 react first in water to generate C2F5CHN2, that participates in a [3 + 2] cycloaddition with electron-deficient alkynes in dichloromethane. PMID:25670987

  12. Exploring the Potential of Diarylacetylenediols as Hydrogen Bonding Catalysts

    PubMed Central

    Türkmen, Yunus E.; Rawal, Viresh H.

    2014-01-01

    In the course of a search for new classes of hydrogen bonding catalysts, we have examined diarylacetylenediols as potential catalysts for the Diels-Alder reaction. General and efficient methods have been developed for the preparation of these diols. Their structures were systematically modified and increased activity was observed for those possessing an electron-withdrawing group on the aryl groups. The electron-deficient diarylacetylenediol catalysts, while more active, undergo spontaneous cyclization to the corresponding benzo[b]furans. A mechanism is postulated to explain this facile transformation. Computational studies performed on 2-ethynylphenol help to explain the effect of the alkyne on the conformation and hydrogen bond donating ability of the adjacent OH group. Finally, the crystal structure of one of the diols is reported, and it displays an intricate network of intermolecular hydrogen bonds. PMID:23869597

  13. Bond Issues.

    ERIC Educational Resources Information Center

    Pollack, Rachel H.

    2000-01-01

    Notes trends toward increased borrowing by colleges and universities and offers guidelines for institutions that are considering issuing bonds to raise money for capital projects. Discussion covers advantages of using bond financing, how use of bonds impacts on traditional fund raising, other cautions and concerns, and some troubling aspects of…

  14. Multiple bonds between transition metals and main-group elements. 73. Synthetic routes to rhenium(V) alkyl and rhenium(VII) alkylidyne complexes. X-ray crystal structures of (. eta. sup 5 -C sub 5 Me sub 5 )Re( double bond O)(CH sub 3 )(CH sub 2 C(CH sub 3 ) sub 3 ) and (. eta. sup 5 -C sub 5 Me sub 5 )(Br) sub 3 Re triple bond CC(CH sub 3 ) sub 3

    SciTech Connect

    Herrmann, W.A.; Felixberger, J.K.; Anwander, R.; Herdtweck, E.; Kiprof, P.; Riede, J. )

    1990-05-01

    Dialkyloxo({eta}{sup 5}pentamethylcyclopentadienyl)rhenium(V) complexes ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(CH{sub 3})R{prime}(R{prime} = C{sub 2}H{sub 5}, CH{sub 2}Si(CH{sub 3}){sub 3}, CH{sub 2}C(CH{sub 3}){sub 3}), 1c-e, have become accessible through alkylation of ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(Cl)(CH{sub 3}) (7) with R{prime}MgCl. 1c-e are the first rhenium complexes containing different alkyl ligands. The neopentyl derivative 1e (R{prime} = CH{sub 2}C(CH{sub 3}){sub 3}) crystallizes in the orthorhombic space group Pbca with a = 960.7 (2), b = 2.844.5 (4), c = 1,260.7 (2) pm, and Z = 8. The X-ray crystal structure was refined to R{sub W} = 3.9%. The chiral molecule shows a distorted tetrahedral geometry around the rhenium center. The tribromide 3b has been structurally characterized. Brown crystals of 3b belong to space group P2{sub 1}/c with unit cell dimensions a = 1,311.5 (2), b = 723.0 (1), c = 1,901.6 (2) pm, {beta} = 92.68 (1){degree}, and Z = 4. The structure exhibits a four-legged piano stool geometry with no trans influence of the neopentylidyne ligand to the bromine atom.

  15. Rb(16)Cd(25.39(3))sb(36): an electron-deficient zintl phase containing infinite dodecahedron chains.

    PubMed

    Zheng, Wu-Zui; Wang, Peng; Wu, Li-Ming; Liu, Yi; Chen, Ling

    2010-07-01

    A novel ternary antimonide Rb(16)Cd(25.39(3))Sb(36) has been synthesized by a solid-state reaction of the appropriate amount of elements in a welded niobium tube at 530 degrees C. The compound crystallizes in orthorhombic space group Cmcm (No. 63) with a = 16.499(5) A, b = 12.391(4) A, c = 12.400(4) A, and Z = 1. The structure features a new 3D network constructed of chains of Rb(+)-centered dodecahedra running along [001]. The atomic distribution of the Cd(8)Sb(12) dodecahedron presents an energetically favored pattern without any Cd-Cd bonding. The formation of the phase and the occurrence of a very narrow phase width of Rb(16)Cd(24+x)Sb(36) [0.94(2) < or = x < or = 1.47(3)] have been studied in detail. The Fermi level of the title compound is expected to be located between those of the hypothetical models of "[Rb(16)Cd(24)Sb(36)](0)" (I, poor metallic) and "[Rb(16)Cd(24)Sb(36)] + 4e" (II, narrow-band-gap semiconductor), which agrees well with the experimental measurements. In the temperature range of 300-473 K, the as-synthesized Rb(16)Cd(25.39(3))Sb(36) exhibits p-type semiconductor behavior and shows temperature-independent thermal conductivities (around 0.49 W/m.K). The electrical conductivity, Seebeck coefficient, and figure of merit (ZT) of Rb(16)Cd(25.39(3))Sb(36) are temperature-dependent; these values are 57.4 S/cm, +81.4 microV/K, and 0.04, respectively, at 466 K. PMID:20509601

  16. Institutional Bonding.

    ERIC Educational Resources Information Center

    Allard, M. June

    Institutional bonding was examined at a public, urban commuter college with exceptionally high attrition and visibly low morale. Changes in bonding and attrition were measured 6 years after a 2-year effort to develop school identity and student feelings of membership. It was found that a simple index of campus morale is provided by level of…

  17. Effective End Group Modification of Poly(3-hexylthiophene) with Functional Electron-Deficient Moieties for Performance Improvement in Polymer Solar Cell.

    PubMed

    Chen, Chi-Min; Jen, Tzu-Hao; Chen, Show-An

    2015-09-23

    A series of end-functionalized poly(3-hexylthiophene)s (P3HTs) were synthesized by end-capping with electron-deficient moieties (EDMs, oxadiazole (OXD) and triazole (TAZ)) to prevent the negative influence of bromine chain ends in the common uncapped P3HT in polymer solar cell (PSC) applications. On the basis of the electron-withdrawing capability of the planar OXD end groups, P3HT-end-OXD relative to the uncapped P3HT exhibits a raised absorption coefficient, extended exciton lifetime, and increased crystalline order in the blend with PCBM, leading to an effectual improvement in photovoltaic parameters. However, P3HT-end-TAZ has an opposite result even worse than that of the uncapped P3HT, arising from bulky TAZ end groups. As a consequence, P3HT-end-OXD gives a power conversion efficiency (PCE) of 4.24%, which is higher than those of the uncapped P3HT (3.28%) and P3HT-end-TAZ (0.50%). The result demonstrates that the EDM modification is a valuable method to tailor the structural defect of polymer chain ends. However, the efficacy is dependent on the structure of EDM. PMID:26302457

  18. Organic chemistry: No double bond left behind

    NASA Astrophysics Data System (ADS)

    Sarlah, David

    2016-03-01

    Alkenyl halides are some of the most useful building blocks for synthesizing small organic molecules. A catalyst has now allowed their direct preparation from widely available alkenes using the cross-metathesis reaction. See Article p.459

  19. Creating σ-holes through the formation of beryllium bonds.

    PubMed

    Brea, Oriana; Mó, Otilia; Yáñez, Manuel; Alkorta, Ibon; Elguero, José

    2015-09-01

    Through the use of ab initio theoretical models based on MP2/aug-cc-pVDZ-optimized geometries and CCSD(T)/aug-cc-pVTZ and CCSD(T)/aug-c-pVDZ total energies, it has been shown that the significant electron density rearrangements that follow the formation of a beryllium bond may lead to the appearance of a σ-hole in systems that previously do not exhibit this feature, such as CH3 OF, NO2 F, NO3 F, and other fluorine-containing systems. The creation of the σ-hole is another manifestation of the bond activation-reinforcement (BAR) rule. The appearance of a σ-hole on the F atoms of CH3 OF is due to the enhancement of the electronegativity of the O atom that participates in the beryllium bond. This atom recovers part of the charge transferred to Be by polarizing the valence density of the F into the bonding region. An analysis of the electron density shows that indeed this bond becomes reinforced, but the F atom becomes more electron deficient with the appearance of the σ-hole. Importantly, similar effects are also observed even when the atom participating in the beryllium bond is not directly attached to the F atom, as in NO2 F, NO3 F, or NCF. Hence, whereas the isolated CH3 OF, NO2 F, and NO3 F are unable to yield F⋅⋅⋅Base halogen bonds, their complexes with BeX2 derivatives are able to yield such bonds. Significant cooperative effects between the new halogen bond and the beryllium bond reinforce the strength of both noncovalent interactions. PMID:26212472

  20. Distinguishing Bonds.

    PubMed

    Rahm, Martin; Hoffmann, Roald

    2016-03-23

    The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Δχ̅ and Δ(VNN + ω)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Q itself shows a set of interesting relations with the correlation energy of a bond. PMID:26910496

  1. Yankee bonds

    SciTech Connect

    Delaney, P. )

    1993-10-01

    Yankee and Euromarket bonds may soon find their way into the financing of power projects in Latin America. For developers seeking long-term commitments under build, own, operate, and transfer (BOOT) power projects in Latin America, the benefits are substantial.

  2. Annulation of Aromatic Imines via Directed C-H BondActivation

    SciTech Connect

    Thalji, Reema K.; Ahrendt, Kateri A.; Bergman, Robert G.; Ellman,Jonathan A.

    2005-04-14

    A directed C-H bond activation approach to the synthesis of indans, tetralins, dihydrofurans, dihydroindoles, and other polycyclic aromatic compounds is presented. Cyclization of aromatic ketimines and aldimines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using (PPh{sub 3}){sub 3}RhCl (Wilkinson's catalyst). The cyclization of a range of aromatic ketimines and aldimines provides bi- and tricyclic ring systems with good regioselectivity. Different ring sizes and substitution patterns can be accessed through the coupling of monosubstituted, 1,1- or 1,2-disubstituted, and trisubstituted alkenes bearing both electron-rich and electron-deficient functionality.

  3. Annulation of aromatic imines via directed C-H bond activation.

    PubMed

    Thalji, Reema K; Ahrendt, Kateri A; Bergman, Robert G; Ellman, Jonathan A

    2005-08-19

    A directed C-H bond activation approach to the synthesis of indans, tetralins, dihydrofurans, dihydroindoles, and other polycyclic aromatic compounds is presented. Cyclization of aromatic ketimines and aldimines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using (PPh3)3RhCl (Wilkinson's catalyst). The cyclization of a range of aromatic ketimines and aldimines provides bi- and tricyclic ring systems with good regioselectivity. Different ring sizes and substitution patterns can be accessed through the coupling of monosubstituted, 1,1- or 1,2-disubstituted, and trisubstituted alkenes bearing both electron-rich and electron-deficient functionality. PMID:16095296

  4. Multiple-Bond Kinetics from Single-Molecule Pulling Experiments: Evidence for Multiple NCAM Bonds

    PubMed Central

    Hukkanen, E. J.; Wieland, J. A.; Gewirth, A.; Leckband, D. E.; Braatz, R. D.

    2005-01-01

    The kinetic parameters of single bonds between neural cell adhesion molecules were determined from atomic force microscope measurements of the forced dissociation of the homophilic protein-protein bonds. The analytical approach described provides a systematic procedure for obtaining rupture kinetics for single protein bonds from bond breakage frequency distributions obtained from single-molecule pulling experiments. For these studies, we used the neural cell adhesion molecule (NCAM), which was recently shown to form two independent protein bonds. The analysis of the bond rupture data at different loading rates, using the single-bond full microscopic model, indicates that the breakage frequency distribution is most sensitive to the distance to the transition state and least sensitive to the molecular spring constant. The analysis of bond failure data, however, motivates the use of a double-bond microscopic model that requires an additional kinetic parameter. This double-bond microscopic model assumes two independent NCAM-NCAM bonds, and more accurately describes the breakage frequency distribution, particularly at high loading rates. This finding agrees with recent surface-force measurements, which showed that NCAM forms two spatially distinct bonds between opposed proteins. PMID:16100278

  5. The Quadruple Bonding in C2 Reproduces the Properties of the Molecule.

    PubMed

    Shaik, Sason; Danovich, David; Braida, Benoit; Hiberty, Philippe C

    2016-03-14

    Ever since Lewis depicted the triple bond for acetylene, triple bonding has been considered as the highest limit of multiple bonding for main elements. Here we show that C2 is bonded by a quadruple bond that can be distinctly characterized by valence-bond (VB) calculations. We demonstrate that the quadruply-bonded structure determines the key observables of the molecule, and accounts by itself for about 90% of the molecule's bond dissociation energy, and for its bond lengths and its force constant. The quadruply-bonded structure is made of two strong π bonds, one strong σ bond and a weaker fourth σ-type bond, the bond strength of which is estimated as 17-21 kcal mol(-1). Alternative VB structures with double bonds; either two π bonds or one π bond and one σ bond lie at 129.5 and 106.1 kcal mol(-1), respectively, above the quadruply-bonded structure, and they collapse to the latter structure given freedom to improve their double bonding by dative σ bonding. The usefulness of the quadruply-bonded model is underscored by "predicting" the properties of the (3)Σ+u state. C2's very high reactivity is rooted in its fourth weak bond. Thus, carbon and first-row main elements are open to quadruple bonding! PMID:26880488

  6. Diffusion bonding

    DOEpatents

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  7. Constructing Models in Teaching of Chemical Bonds: Ionic Bond, Covalent Bond, Double and Triple Bonds, Hydrogen Bond and Molecular Geometry

    ERIC Educational Resources Information Center

    Uce, Musa

    2015-01-01

    Studies in chemistry education show that chemistry topics are considered as abstract, complicated and hard to understand by students. For this reason, it is important to develop new materials and use them in classes for better understanding of abstract concepts. Moving from this point, a student-centered research guided by a teacher was conducted…

  8. Functionalized olefin cross-coupling to construct carbon–carbon bonds

    PubMed Central

    Lo, Julian C.; Gui, Jinghan; Yabe, Yuki; Pan, Chung-Mao; Baran, Phil S.

    2014-01-01

    Carbon–carbon (C–C) bonds form the backbone of many important molecules, including polymers, dyes, and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavor heavily relies on the ability to form C–C bonds in the presence of sensitive functional groups and congested structural environments. Here we report a fundamentally new chemical transformation that allows for the facile construction of highly substituted and uniquely functionalized C–C bonds. Using a simple iron catalyst, an inexpensive silane, and a benign solvent under an ambient atmosphere, heteroatom-substituted olefins are easily merged with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than sixty examples are presented with a wide array of substrates, demonstrating the unique chemoselectivity and mildness of this simple reaction. PMID:25519131

  9. Functionalized olefin cross-coupling to construct carbon-carbon bonds

    NASA Astrophysics Data System (ADS)

    Lo, Julian C.; Gui, Jinghan; Yabe, Yuki; Pan, Chung-Mao; Baran, Phil S.

    2014-12-01

    Carbon-carbon (C-C) bonds form the backbone of many important molecules, including polymers, dyes and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavour relies heavily on the ability to form C-C bonds in the presence of sensitive functional groups and congested structural environments. Here we report a chemical transformation that allows the facile construction of highly substituted and uniquely functionalized C-C bonds. Using a simple iron catalyst, an inexpensive silane and a benign solvent under ambient atmosphere, heteroatom-substituted olefins are easily reacted with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than 60 examples are presented with a wide array of substrates, demonstrating the chemoselectivity and mildness of this simple reaction.

  10. Exocyclic push-pull conjugated compounds. Part 3. An experimental NMR and theoretical MO ab initio study of the structure, the electronic properties and barriers to rotation about the exocyclic partial double bond in 2- exo-methylene- and 2-cyanoimino-quinazolines and -benzodiazepines

    NASA Astrophysics Data System (ADS)

    Benassi, R.; Bertarini, C.; Hilfert, L.; Kempter, G.; Kleinpeter, E.; Spindler, J.; Taddei, F.; Thomas, S.

    2000-03-01

    The structure of a number of 2- exo-methylene substituted quinazolines and benzodiazepines, respectively, 1, 3a, b, 4( X=-CN, -COOEt ) and their 2-cyanoimino substituted analogues 2, 3c, d( X=-CN, -SO 2C 6H 4-Me (p) was completely assigned by the whole arsenal of 1D and 2D NMR spectroscopic methods. The E/ Z isomerism at the exo-cyclic double bond was determined by both NMR spectroscopy and confirmed by ab initio quantum chemical calculations; the Z isomer is the preferred one, its amount proved dependent on steric hindrance. Due to the push-pull effect in this part of the molecules the restricted rotation about the partial C 2,C 11 and C 2,N 11 double bonds, could also be studied and the barrier to rotation measured by dynamic NMR spectroscopy. The free energies of activation of this dynamic process proved very similar along the compounds studied but being dependent on the polarity of the solvent. Quantum chemical calculations at the ab initio level were employed to prove the stereochemistry at the exo-cyclic partial double bonds of 1- 4, to calculate the barriers to rotation but also to discuss in detail both the ground and the transition state of the latter dynamic process in order to better understand electronic, inter- and intramolecular effects on the barrier to rotation which could be determined experimentally. In the cyanoimino substituted compounds 2, 3c, d, the MO ab initio calculations evidence the isomer interconversion to be better described by the internal rotation process than by the lateral shift mechanism.

  11. Pi Bond Orders and Bond Lengths

    ERIC Educational Resources Information Center

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

    Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)

  12. Bonded Lubricants

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Another spinoff to the food processing industry involves a dry lubricant developed by General Magnaplate Corp. of Linden, N.J. Used in such spacecraft as Apollo, Skylab and Viking, the lubricant is a coating bonded to metal surfaces providing permanent lubrication and corrosion resistance. The coating lengthens equipment life and permits machinery to be operated at greater speed, thus increasing productivity and reducing costs. Bonded lubricants are used in scores of commercia1 applications. They have proved particularly valuable to food processing firms because, while increasing production efficiency, they also help meet the stringent USDA sanitation codes for food-handling equipment. For example, a cookie manufacturer plagued production interruptions because sticky batter was clogging the cookie molds had the brass molds coated to solve the problem. Similarly, a pasta producer faced USDA action on a sanitation violation because dough was clinging to an automatic ravioli-forming machine; use of the anti-stick coating on the steel forming plates solved the dual problem of sanitation deficiency and production line downtime.

  13. Substituent Effects on the [N-I-N](+) Halogen Bond.

    PubMed

    Carlsson, Anna-Carin C; Mehmeti, Krenare; Uhrbom, Martin; Karim, Alavi; Bedin, Michele; Puttreddy, Rakesh; Kleinmaier, Roland; Neverov, Alexei A; Nekoueishahraki, Bijan; Gräfenstein, Jürgen; Rissanen, Kari; Erdélyi, Máté

    2016-08-10

    We have investigated the influence of electron density on the three-center [N-I-N](+) halogen bond. A series of [bis(pyridine)iodine](+) and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine](+) BF4(-) complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by (15)N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N-I-N](+) halogen bond resulted in >100 ppm (15)N NMR coordination shifts. Substituent effects on the (15)N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N-I-N](+) halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine](+) complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N](+) bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N-I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N-X-N](+) halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen](+)-type synthetic reagents. PMID:27265247

  14. Substituent Effects on the [N–I–N]+ Halogen Bond

    PubMed Central

    2016-01-01

    We have investigated the influence of electron density on the three-center [N–I–N]+ halogen bond. A series of [bis(pyridine)iodine]+ and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine]+ BF4– complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by 15N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N–I–N]+ halogen bond resulted in >100 ppm 15N NMR coordination shifts. Substituent effects on the 15N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N–I–N]+ halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine]+ complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N]+ bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N–I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N–X–N]+ halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen]+-type synthetic reagents. PMID:27265247

  15. Basics of Fidelity Bonding.

    ERIC Educational Resources Information Center

    Kahn, Steven P.

    Fidelity bonds are important for an agency to hold to protect itself against any financial loss that can result from dishonest acts by its employees. Three types of fidelity bonds are available to an agency: (1) public official bonds; (2) dishonesty bonds; and (3) faithful performance bonds. Public official bonds are required by state law to be…

  16. Chiral Aminophosphines as Catalysts for Enantioselective Double-Michael Indoline Syntheses

    PubMed Central

    Khong, San N.; Kwon, Ohyun

    2014-01-01

    The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between ortho-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction. PMID:22580397

  17. Bonded boojum-colloids in nematic liquid crystals.

    PubMed

    Eskandari, Zahra; Silvestre, Nuno M; Telo da Gama, Margarida M

    2013-08-20

    We investigate bonded boojum-colloids in nematic liquid crystals, configurations where two colloids with planar degenerate anchoring are double-bonded through line defects connecting their surfaces. This bonded structure promotes the formation of linear chains aligned with the nematic director. We show that the bonded configuration is the global minimum in systems that favor twist deformations. In addition, we investigate the influence of confinement on the stability of bonded boojum-colloids. Although the unbonded colloid configuration, where the colloids bundle at oblique angles, is favored by confinement, the bonded configuration is again the global minimum for liquid crystals with sufficiently small twist elastic constants. PMID:23859624

  18. Stereochemistry of enzymatic water addition to C=C bonds.

    PubMed

    Chen, Bi-Shuang; Otten, Linda G; Hanefeld, Ulf

    2015-01-01

    Water addition to carbon-carbon double bonds using hydratases is attracting great interest in biochemistry. Most of the known hydratases are involved in primary metabolism and to a lesser extent in secondary metabolism. New hydratases have recently been added to the toolbox, both from natural sources or artificial metalloenzymes. In order to comprehensively understand how the hydratases are able to catalyse the water addition to carbon-carbon double bonds, this review will highlight the mechanistic and stereochemical studies of the enzymatic water addition to carbon-carbon double bonds, focusing on the syn/anti-addition and stereochemistry of the reaction. PMID:25640045

  19. A General Method for Aminoquinoline-Directed, Copper-Catalyzed sp(2) C-H Bond Amination.

    PubMed

    Roane, James; Daugulis, Olafs

    2016-04-01

    An operationally simple and general method for copper-catalyzed, aminoquinoline-assisted amination of β-C(sp(2))-H bonds of benzoic acid derivatives is reported. The reaction employs Cu(OAc)2 or (CuOH)2CO3 catalysts, an amine coupling partner, and oxygen from air as a terminal oxidant. Exceptionally high generality with respect to amine coupling partners is observed. Specifically, primary and secondary aliphatic and aromatic amines, heterocycles, such as indoles, pyrazole, and carbazole, sulfonamides, as well as electron-deficient aromatic and heteroaromatic amines are competent coupling components. PMID:26990413

  20. In-silico bonding schemes to encode chemical bonds involving sharing of electrons in molecular structures.

    PubMed

    Punnaivanam, Sankar; Sathiadhas, Jerome Pastal Raj; Panneerselvam, Vinoth

    2016-05-01

    Encoding of covalent and coordinate covalent bonds in molecular structures using ground state valence electronic configuration is achieved. The bonding due to electron sharing in the molecular structures is described with five fundamental bonding categories viz. uPair-uPair, lPair-uPair, uPair-lPair, vPair-lPair, and lPair-lPair. The involvement of lone pair electrons and the vacant electron orbitals in chemical bonding are explained with bonding schemes namely "target vacant promotion", "source vacant promotion", "target pairing promotion", "source pairing promotion", "source cation promotion", "source pairing double bond", "target vacant occupation", and "double pairing promotion" schemes. The bonding schemes are verified with a chemical structure editor. The bonding in the structures like ylides, PCl5, SF6, IF7, N-Oxides, BF4(-), AlCl4(-) etc. are explained and encoded unambiguously. The encoding of bonding in the structures of various organic compounds, transition metals compounds, coordination complexes and metal carbonyls is accomplished. PMID:27041446

  1. Chemical Bonds II

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    The continuation of a paper discussing chemical bonding from a bond energy viewpoint, with a number of examples of single and multiple bonds. (Part I appeared in volume 1 number 3, pages 16-23, February 1972.) (AL)

  2. What Determines Bond Costs. Municipal Bonds Series.

    ERIC Educational Resources Information Center

    Young, Douglas; And Others

    Public officials in small towns who participate infrequently in the bond market need information about bond financing. This publication, one in a series of booklets published by the Western Rural Development Center using research gathered between 1967-77, discusses factors influencing the marketability and cost of bond financing for towns and…

  3. Protocols for the selective cleavage of carbon-sulfur bonds in coal

    SciTech Connect

    Bausch, M.

    1991-01-01

    Removal of the organic sulfur in coal constitutes one of the major challenges facing fossil fuel scientists today. A cost--effective of desulfurizing Illinois coal is non-existent at the present time. Research in our group aims to develop a simple protocol for sulfur removal by gaining understanding of how various additives can enhance the rates of C-S bond cleavage in Illinois coal and coal model compounds, relative to fragmentation of the coal macromolecule via C-C, C-O, and C-N bond cleavage. During this funding period, we plan to carry out examinations of: (a) the effects of various reaction conditions on radical-initiated and Lewis acid-catalyzed C-S bond cleavages; (b) the effects of caustic impregnation and subsequent alcoholic reflux on C-S bond cleavage strategies; (c) the reactions of coal model compounds with electron-deficient substrates; (d) examinations of photooxidative C-S bond cleavage reactions; (e) the effects of moderate (300--400{degrees}C) temperatures and pressures as well as ultrasonic radiation on (a) - (c). Also planned are differential scanning calorimetric (DSC) examinations of selected C-S bond cleavage protocols, including those on Illinois coals that possess varying amounts of organic and inorganic sulfur.

  4. The direct arylation of allylic sp3 C–H bonds via organocatalysis and photoredox catalysis

    PubMed Central

    Cuthbertson, James D.; MacMillan, David W. C.

    2015-01-01

    The direct functionalization of unactivated sp3 C–H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts,1 the establishment of general and mild strategies for the engagement of sp3 C–H bonds in carbon–carbon bond forming reactions has proven difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene, and methine carbons in a catalytic manner is a priority. While protocols for direct allylic C–H oxidation and amination have become widely established,2,3 the engagement of allylic substrates in carbon–carbon bond-forming reactions has thus far required the use of pre-functionalized coupling partners.4 In particular, the direct arylation of non-functionalized allylic systems would enable chemists to rapidly access a series of known pharmacophores, though a general solution to this longstanding challenge remains elusive. We describe herein the use of both photoredox and organic catalysis to accomplish the first mild, broadly effective direct allylic C–H arylation. This new C–C bond-forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants and has been used in the direct arylation of benzylic C–H bonds. PMID:25739630

  5. Rhodium(III)-Catalyzed Tandem [2+2+2] Annulation-Lactamization of Anilides with Two Alkynoates via Cleavage of Two Adjacent C-H or C-H/C-O bonds.

    PubMed

    Fukui, Miho; Shibata, Yu; Hoshino, Yuki; Sugiyama, Haruki; Teraoka, Kota; Uekusa, Hidehiro; Noguchi, Keiichi; Tanaka, Ken

    2016-08-19

    An electron-deficient Cp(E) rhodium(III) complex bearing a cyclopentadienyl ligand with two ethyl ester substituents catalyzes the tandem [2+2+2] annulation-lactamization of acetanilides with two alkynoates via cleavage of adjacent two C-H bonds to give densely substituted benzo[cd]indolones. The reactions of meta-methoxy-substituted acetanilides with two alkynoates also provided benzo[cd]indolones via cleavage of adjacent C-H/C-O bonds. Furthermore, 3,5-dimethoxyacetanilides reacted with two alkynoates to give dearomatized spiro compounds. PMID:27412046

  6. Using Multiple Bonding Strategies.

    PubMed

    Larson, Thomas D

    2015-01-01

    There are many ways to bond to tooth structure, some micro-mechanical some chemical, some a combination. Different dentin bonding materials have different bonding strengths to differently prepared surfaces, and because of differences in their nature, different areas of tooth structure present peculiar bonding challenges. This paper will review a variety of material types, elucidating their particular bonding strengths and commenting on improved bonding strategies to increase durability, strength, and favorable pulpal response. In this discussion, resin dentin bonding systems, glass ionomers, Gluma, resin cements, and newer combined products will br reviewed. PMID:26485903

  7. Double stranded nucleic acid biochips

    DOEpatents

    Chernov, Boris; Golova, Julia

    2006-05-23

    This invention describes a new method of constructing double-stranded DNA (dsDNA) microarrays based on the use of pre-synthesized or natural DNA duplexes without a stem-loop structure. The complementary oligonucleotide chains are bonded together by a novel connector that includes a linker for immobilization on a matrix. A non-enzymatic method for synthesizing double-stranded nucleic acids with this novel connector enables the construction of inexpensive and robust dsDNA/dsRNA microarrays. DNA-DNA and DNA-protein interactions are investigated using the microarrays.

  8. The direct arylation of allylic sp3 C-H bonds via organic and photoredox catalysis

    NASA Astrophysics Data System (ADS)

    Cuthbertson, James D.; MacMillan, David W. C.

    2015-03-01

    The direct functionalization of unactivated sp3 C-H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts, the establishment of general and mild strategies for the engagement of sp3 C-H bonds in C-C bond forming reactions has proved difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene and methine carbons in a catalytic manner is a priority. Although protocols for direct oxidation and amination of allylic C-H bonds (that is, C-H bonds where an adjacent carbon is involved in a C = C bond) have become widely established, the engagement of allylic substrates in C-C bond forming reactions has thus far required the use of pre-functionalized coupling partners. In particular, the direct arylation of non-functionalized allylic systems would enable access to a series of known pharmacophores (molecular features responsible for a drug's action), though a general solution to this long-standing challenge remains elusive. Here we report the use of both photoredox and organic catalysis to accomplish a mild, broadly effective direct allylic C-H arylation. This C-C bond forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants, and has been used in the direct arylation of benzylic C-H bonds.

  9. The direct arylation of allylic sp(3) C-H bonds via organic and photoredox catalysis.

    PubMed

    Cuthbertson, James D; MacMillan, David W C

    2015-03-01

    The direct functionalization of unactivated sp(3) C-H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts, the establishment of general and mild strategies for the engagement of sp(3) C-H bonds in C-C bond forming reactions has proved difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene and methine carbons in a catalytic manner is a priority. Although protocols for direct oxidation and amination of allylic C-H bonds (that is, C-H bonds where an adjacent carbon is involved in a C = C bond) have become widely established, the engagement of allylic substrates in C-C bond forming reactions has thus far required the use of pre-functionalized coupling partners. In particular, the direct arylation of non-functionalized allylic systems would enable access to a series of known pharmacophores (molecular features responsible for a drug's action), though a general solution to this long-standing challenge remains elusive. Here we report the use of both photoredox and organic catalysis to accomplish a mild, broadly effective direct allylic C-H arylation. This C-C bond forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants, and has been used in the direct arylation of benzylic C-H bonds. PMID:25739630

  10. From ketones to esters by a Cu-catalyzed highly selective C(CO)-C(alkyl) bond cleavage: aerobic oxidation and oxygenation with air.

    PubMed

    Huang, Xiaoqiang; Li, Xinyao; Zou, Miancheng; Song, Song; Tang, Conghui; Yuan, Yizhi; Jiao, Ning

    2014-10-22

    The Cu-catalyzed aerobic oxidative esterification of simple ketones via C-C bond cleavage has been developed. Varieties of common ketones, even inactive aryl long-chain alkyl ketones, are selectively converted into esters. The reaction tolerates a wide range of alcohols, including primary and secondary alcohols, chiral alcohols with retention of the configuration, electron-deficient phenols, as well as various natural alcohols. The usage of inexpensive copper catalyst, broad substrate scope, and neutral and open air conditions make this protocol very practical. (18)O labeling experiments reveal that oxygenation occurs during this transformation. Preliminary mechanism studies indicate that two novel pathways are mainly involved in this process. PMID:25251943

  11. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Use of existing bonds, separate bonds and additional..., separate bonds and additional bonding. (a) Additional bonding. Section 13 neither prevents additional... or separate bond. (b) Use of existing bonds. Insofar as a bond currently in use is adequate to...

  12. Hydroxide-catalyzed bonding

    NASA Technical Reports Server (NTRS)

    Gwo, Dz-Hung (Inventor)

    2003-01-01

    A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

  13. Computational Characterization of Adhesive Bond Properties Using Guided Waves in Bonded Plates

    NASA Astrophysics Data System (ADS)

    Koreck, Juergen; Valle, Christine; Qu, Jianmin; Jacobs, Laurence J.

    2007-03-01

    This research focuses on the application of guided waves techniques to nondestructively characterize the structural integrity of bonded engineering components. Computational methods are used to examine the properties of double-layered, adhesive bonded plates. This study quantifies the effect of the adhesive bond parameters (Young's modulus, Poisson's ratio and bond thickness) on the dispersion curves. A commercial finite element (FE) code (ABAQUS/Explicit) is used for the numerical model while the global matrix method (GMM) is used to benchmark the resulting dispersion relationships in the form of a frequency-wavenumber or slowness-frequency relation. In the dispersion relations, a set of bond parameter sensitive and FE-visible points is selected. The frequency locations of these points represent the solution criteria for the inversion procedure based on the global matrix method. The capabilities of the inversion process depend on the number of transient output signals from a FE simulation for the forward problem.

  14. New NMR spectroscopic probe of the absolute stereoselectivity for metal-hydride and metal-alkyl additions to the carbon-carbon double bond. Demonstration with a single-component, isospecific Ziegler-Natta {alpha}-olefin polymerization catalyst

    SciTech Connect

    Gilchrist, J.H.; Bercaw, J.E.

    1996-12-04

    Optically active (98% ee) (R)-1,1,3,4,4,5,5,5-octadeutero-1-pentene (1) was prepared and used to evaluate the stereoselectivity of Y-H and Y-n-pentyl additions for the optically pure C{sub 2}-symmetric (R,S)-(BnBp)Y-R/(S,R)-(BnBp)Y-R and racemic ({+-})-(BnBp)Y-R isospecific polypropylene catalysts (BnBp = [(OC{sub 10}H{sub 6}C{sub 10}H{sub 6}O)Si(C{sub 5}H{sub 2}-2-SiMe{sub 3}-4-CMe{sub 3}){sub 2}]). Deuteration and deuterodimerization of 1 mediated by (R,S)-, (S,R)-, and ({+-})-(BnBp)Y-D provide alkanes whose {sup 1}H NMR spectra indicate the sense and magnitude of olefin facial selectivity for insertions into metal-hydride and metal-n-pentyl bonds. It is shown that useful information concerning the stereochemistry of olefin insertion can be deduced from the {sup 2}H NMR spectra of 1-pentene deuterodimers without the requirement of a stereochemically labeled pentene or a resolved catalyst. 26 refs., 4 figs.

  15. Double Layers in Astrophysics

    NASA Technical Reports Server (NTRS)

    Williams, Alton C. (Editor); Moorehead, Tauna W. (Editor)

    1987-01-01

    Topics addressed include: laboratory double layers; ion-acoustic double layers; pumping potential wells; ion phase-space vortices; weak double layers; electric fields and double layers in plasmas; auroral double layers; double layer formation in a plasma; beamed emission from gamma-ray burst source; double layers and extragalactic jets; and electric potential between plasma sheet clouds.

  16. Diffusion bonding aeroengine components

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, G. A.; Broughton, T.

    1988-10-01

    The use of diffusion bonding processes at Rolls-Royce for the manufacture of titanium-alloy aircraft engine components and structures is described. A liquid-phase diffusion bonding process called activated diffusion bonding has been developed for the manufacture of the hollow titanium wide chord fan blade. In addition, solid-state diffusion bonding is being used in the manufacture of hollow vane/blade airfoil constructions mainly in conjunction with superplastic forming and hot forming techniques.

  17. Double screening

    NASA Astrophysics Data System (ADS)

    Gratia, Pierre; Hu, Wayne; Joyce, Austin; Ribeiro, Raquel H.

    2016-06-01

    Attempts to modify gravity in the infrared typically require a screening mechanism to ensure consistency with local tests of gravity. These screening mechanisms fit into three broad classes; we investigate theories which are capable of exhibiting more than one type of screening. Specifically, we focus on a simple model which exhibits both Vainshtein and kinetic screening. We point out that due to the two characteristic length scales in the problem, the type of screening that dominates depends on the mass of the sourcing object, allowing for different phenomenology at different scales. We consider embedding this double screening phenomenology in a broader cosmological scenario and show that the simplest examples that exhibit double screening are radiatively stable.

  18. Rapid adhesive bonding concepts

    NASA Technical Reports Server (NTRS)

    Stein, B. A.; Tyeryar, J. R.; Hodges, W. T.

    1984-01-01

    Adhesive bonding in the aerospace industry typically utilizes autoclaves or presses which have considerable thermal mass. As a consequence, the rates of heatup and cooldown of the bonded parts are limited and the total time and cost of the bonding process is often relatively high. Many of the adhesives themselves do not inherently require long processing times. Bonding could be performed rapidly if the heat was concentrated in the bond lines or at least in the adherends. Rapid adhesive bonding concepts were developed to utilize induction heating techniques to provide heat directly to the bond line and/or adherends without heating the entire structure, supports, and fixtures of a bonding assembly. Bonding times for specimens are cut by a factor of 10 to 100 compared to standard press bonding. The development of rapid adhesive bonding for lap shear specimens (per ASTM D1003 and D3163), for aerospace panel bonding, and for field repair needs of metallic and advanced fiber reinforced polymeric matrix composite structures are reviewed.

  19. Explosives sensing by using electron-rich supramolecular polymers: role of intermolecular hydrogen bonding in significant enhancement of sensitivity.

    PubMed

    Gole, Bappaditya; Song, Wentao; Lackinger, Markus; Mukherjee, Partha Sarathi

    2014-10-13

    We demonstrate here that supramolecular interactions enhance the sensitivity towards detection of electron-deficient nitro-aromatic compounds (NACs) over discrete analogues. NACs are the most commonly used explosive ingredients and are common constituents of many unexploded landmines used during World War II. In this study, we have synthesised a series of pyrene-based polycarboxylic acids along with their corresponding discrete esters. Due to the electron richness and the fluorescent behaviour of the pyrene moiety, all the compounds act as sensors for electron-deficient NACs through a fluorescence quenching mechanism. A Stern-Volmer quenching constant determination revealed that the carboxylic acids are more sensitive than the corresponding esters towards NACs in solution. The high sensitivity of the acids was attributed to supramolecular polymer formation through hydrogen bonding in the case of the acids, and the enhancement mechanism is based on an exciton energy migration upon excitation along the hydrogen-bond backbone. The presence of intermolecular hydrogen bonding in the acids in solution was established by solvent-dependent fluorescence studies and dynamic light scattering (DLS) experiments. In addition, the importance of intermolecular hydrogen bonds in solid-state sensing was further explored by scanning tunnelling microscopy (STM) experiments at the liquid-solid interface, in which structures of self-assembled monolayer of the acids and the corresponding esters were compared. The sensitivity tests revealed that these supramolecular sensors can even detect picric acid and trinitrotoluene in solution at levels as low as parts per trillion (ppt), which is much below the recommended permissible level of these constituents in drinking water. PMID:25187022

  20. Ultrasonic NDE of titanium diffusion bonds using signal phase

    NASA Astrophysics Data System (ADS)

    Escobar-Ruiz, E.; Cawley, P.; Nagy, P. B.; Collison, I.; Wright, D.

    2013-01-01

    Diffusion bonding is a highly advantageous solid-state welding method. However, its full exploitation in titanium components is currently limited by a lack of robust NDE techniques capable of detecting anything but gross bond-line defects. A novel ultrasonic technique has been developed to address this lack of capability. This technique, based on the ultrasonic signal phase, has been demonstrated in a `single-sided' scenario where only one side of the diffusion bond was accessible. Samples with differing degrees of bond quality were evaluated, and excellent agreement was found between the single-sided and double-sided experiments.

  1. Synthesis, structure, electronic spectroscopy, photophysics, electrochemistry, and X-ray photoelectron spectroscopy of highly-electron-deficient [5,10,15,20-tetrakis(perfluoroalkyl)porphinato]zinc(II ) complexes and their free base derivatives

    SciTech Connect

    Goll, J.G.; Moore, K.T.; Therien, M.J.; Ghosh, A.

    1996-09-04

    The synthesis, optical spectroscopy, photophysical properties, electrochemistry, and X-ray photoelectron spectroscopy of a series of [5,10,15,20-tetrakis(perfluoroalkyl)porphinato]zinc(II ) complexes and their free base analogs are reported. The title compounds were prepared by a condensation methodology that utilizes perfluoro-1-(2`-pyrrolyl)-1-alkanol precursors and employs continuous water removal throughout the course of the reaction to yield the meso perfluorocarbon-substituted porphyrins. The nature of the porphyrin-pendant meso-perfluoroalkyl group exerts considerable influence over the macrocycle`s solubility properties. The structure of the monopyridyl adduct of [5,10,15,20-tetrakis(heptafluoropropyl)porphinato] zinc(II) features an S{sub 4}-distorted porphyrin core; X-ray data are given. Electrochemical studies carried out on these porphyrin and (porphinato)zinc(II) complexes indicate that meso-perfluoroalkylporphyrins are among the most electron-deficient porphyrinic species known. X-ray photoelectron spectroscopy experiments corroborate the electron poor nature of these systems and evince extreme stabilization of the nitrogen ls orbitals, consonant with particularly effective removal of electron density from the macrocycle by the meso-perfluoroalkyl moieties that is modulated by {sigma}-symmetry orbitals. 27 refs., 8 figs., 6 tabs.

  2. Direct and Auger Electron-Induced, Single- and Double-Strand Breaks on Plasmid DNA Caused by 99mTc-Labeled Pyrene Derivatives and the Effect of Bonding Distance.

    PubMed

    Reissig, Falco; Mamat, Constantin; Steinbach, Joerg; Pietzsch, Hans-Juergen; Freudenberg, Robert; Navarro-Retamal, Carlos; Caballero, Julio; Kotzerke, Joerg; Wunderlich, Gerd

    2016-01-01

    It is evident that 99mTc causes radical-mediated DNA damage due to Auger electrons, which were emitted simultaneously with the known γ-emission of 99mTc. We have synthesized a series of new 99mTc-labeled pyrene derivatives with varied distances between the pyrene moiety and the radionuclide. The pyrene motif is a common DNA intercalator and allowed us to test the influence of the radionuclide distance on damages of the DNA helix. In general, pUC 19 plasmid DNA enables the investigation of the unprotected interactions between the radiotracers and DNA that results in single-strand breaks (SSB) or double-strand breaks (DSB). The resulting DNA fragments were separated by gel electrophoresis and quantified by fluorescent staining. Direct DNA damage and radical-induced indirect DNA damage by radiolysis products of water were evaluated in the presence or absence of the radical scavenger DMSO. We demonstrated that Auger electrons directly induced both SSB and DSB in high efficiency when 99mTc was tightly bound to the plasmid DNA and this damage could not be completely prevented by DMSO, a free radical scavenger. For the first time, we were able to minimize this effect by increasing the carbon chain lengths between the pyrene moiety and the 99mTc nuclide. However, a critical distance between the 99mTc atom and the DNA helix could not be determined due to the significantly lowered DSB generation resulting from the interaction which is dependent on the type of the 99mTc binding motif. The effect of variable DNA damage caused by the different chain length between the pyrene residue and the Tc-core as well as the possible conformations of the applied Tc-complexes was supplemented with molecular dynamics (MD) calculations. The effectiveness of the DNA-binding 99mTc-labeled pyrene derivatives was demonstrated by comparison to non-DNA-binding 99mTcO4-, since nearly all DNA damage caused by 99mTcO4- was prevented by incubating with DMSO. PMID:27583677

  3. The varying nature of fluorine oxygen bonds

    NASA Astrophysics Data System (ADS)

    Julia, Timothy J. Lee; Rice Christopher, E.; Dateo, E.

    The singles and doubles coupled cluster method that includes a per turbational estimate of the effects of connected triple excitations CCSD T together with a triple zeta double polarized TZ2P one particle basis set is used to determine the geometries harmonic frequencies infrared intensities and dipole moments of HOF F O HOOF FOOF ClOOF Agreement with experiment is very good with the exception that the currently accepted experimental assignment of the symmetric and antisymmetric O F stretches in FOOF is shown to be reversed and to be consistent with an earlier experimental study Very accurate heats of formation of HOOF FOOF and ClOOF are also computed using the CCSD T method in conjunction with large atomic natural orbital basis sets The F O bond distances quadratic force constants bond energies and fluorine and oxygen atomic charges from the above five molecules and six previously studied molecules FONO trans FONO cis FONO FOCl FOBr and FON are compared and used to deduce a simple model of F O bonding The unusual relationship between the F O bond distance and quadratic force constant shows that F O bonding is a function of at least three effects which are degree of covalent character degree of ionic character and extent of lone electron pair repulsions All of the data are qualitatively consistent with this simple model The bonding in cis FONO is even more complicated involving also dispersion interactions between fluorine and the terminal oxygen It is suggested that the general importance of lone pair repulsions in F O bonding and the additional importance of intra molecular dispersion interactions explains why many density functionals have difficulty in describing the geometry of cis FONO

  4. Bonding thermoplastic polymers

    DOEpatents

    Wallow, Thomas I.; Hunter, Marion C.; Krafcik, Karen Lee; Morales, Alfredo M.; Simmons, Blake A.; Domeier, Linda A.

    2008-06-24

    We demonstrate a new method for joining patterned thermoplastic parts into layered structures. The method takes advantage of case-II permeant diffusion to generate dimensionally controlled, activated bonding layers at the surfaces being joined. It is capable of producing bonds characterized by cohesive failure while preserving the fidelity of patterned features in the bonding surfaces. This approach is uniquely suited to production of microfluidic multilayer structures, as it allows the bond-forming interface between plastic parts to be precisely manipulated at micrometer length scales. The bond enhancing procedure is easily integrated in standard process flows and requires no specialized equipment.

  5. Prospective bonding applications

    NASA Astrophysics Data System (ADS)

    Ancenay, H.; Benazet, D.

    1981-07-01

    Adhesive bonding in industry and in the laboratory is surveyed and prospects for its wider utilization are assessed. The economic impact of bonding technology on industry is discussed. Research is reviewed, centering on the development of nondestructive testing and inspection techniques. Traditional (wood) as well as new materials susceptible to bonding are considered. Applications in construction and civil engineering, in aeronautics, and in the automobile industry are covered. The use of glues in mechanical constructions, in assembling cylindrical parts, and in metal-metal bonding are examined. Hybrid assembling and bonding of composite materials are included.

  6. Protocols for the selective cleavage of carbon-sulfur bonds in coal. Quarterly report, September 1, 1991--November 30, 1991

    SciTech Connect

    Bausch, M.

    1991-12-31

    Removal of the organic sulfur in coal constitutes one of the major challenges facing fossil fuel scientists today. A cost--effective of desulfurizing Illinois coal is non-existent at the present time. Research in our group aims to develop a simple protocol for sulfur removal by gaining understanding of how various additives can enhance the rates of C-S bond cleavage in Illinois coal and coal model compounds, relative to fragmentation of the coal macromolecule via C-C, C-O, and C-N bond cleavage. During this funding period, we plan to carry out examinations of: (a) the effects of various reaction conditions on radical-initiated and Lewis acid-catalyzed C-S bond cleavages; (b) the effects of caustic impregnation and subsequent alcoholic reflux on C-S bond cleavage strategies; (c) the reactions of coal model compounds with electron-deficient substrates; (d) examinations of photooxidative C-S bond cleavage reactions; (e) the effects of moderate (300--400{degrees}C) temperatures and pressures as well as ultrasonic radiation on (a) - (c). Also planned are differential scanning calorimetric (DSC) examinations of selected C-S bond cleavage protocols, including those on Illinois coals that possess varying amounts of organic and inorganic sulfur.

  7. Simple Bond Cleavage

    SciTech Connect

    Gary S. Groenewold

    2005-08-01

    Simple bond cleavage is a class of fragmentation reactions in which a single bond is broken, without formation of new bonds between previously unconnected atoms. Because no bond making is involved, simple bond cleavages are endothermic, and activation energies are generally higher than for rearrangement eliminations. The rate of simple bond cleavage reactions is a strong function of the internal energy of the molecular ion, which reflects a loose transition state that resembles reaction products, and has a high density of accessible states. For this reason, simple bond cleavages tend to dominate fragmentation reactions for highly energized molecular ions. Simple bond cleavages have negligible reverse activation energy, and hence they are used as valuable probes of ion thermochemistry, since the energy dependence of the reactions can be related to the bond energy. In organic mass spectrometry, simple bond cleavages of odd electron ions can be either homolytic or heterolytic, depending on whether the fragmentation is driven by the radical site or the charge site. Simple bond cleavages of even electron ions tend to be heterolytic, producing even electron product ions and neutrals.

  8. Carbon [bond] hydrogen bond activation by titanium imido complexes. Computational evidence for the role of alkane adducts in selective C [bond] H activation.

    PubMed

    Cundari, Thomas R; Klinckman, Thomas R; Wolczanski, Peter T

    2002-02-20

    This paper reports calculations that probe the role of R (hydrocarbon) and R' (ligand substituent) effects on the reaction coordinate for C [bond] H activation: Ti(OR')(2)(=NR') + RH --> adduct --> transition state --> (OR')(2)Ti(N(H)R')(R). Compounds with R = H, Me, Et, Vy, cPr, Ph, Cy, Bz, and cubyl are studied using quantum (R' = H, SiH(3), SiMe(3)) and classical (R' = Si(t)Bu(3)) techniques. Calculated geometries are in excellent agreement with data for experimental models. There is little variability in the calculated molecular structure of the reactants, products, and most interestingly, transition states as R and R' are changed. Structural flexibility is greatest in the adducts Ti(OR')(2)(=NR')...HR. Despite the small structural changes observed for Ti(OR')(2)(double bond] NR') with different R', significant changes are manifested in calculated electronic properties (the Mulliken charge on Ti becomes more positive and the Ti [double bond] N bond order decreases with larger R'), changes that should facilitate C [bond] H activation. Substantial steric modification of the alkane complex is expected from R [bond] R' interactions, given the magnitude of Delta G(add) and the conformational flexibility of the adduct. Molecular mechanics simulations of Ti(OSi(t)Bu(3))(2)([double bond] NSi(t)Bu(3))...isopentane adducts yield an energy ordering as a function of the rank of the C [bond] H bond coordinated to Ti that is consistent with experimental selectivity patterns. Calculated elimination barriers compare very favorably with experiment; larger SiH(3) and TMS ligand substituents generally yield better agreement with experiment, evidence that the modeling of the major contributions to the elimination barrier (N [bond] H and C [bond] H bond making) is ostensibly correct. Calculations indicate that weakening the C [bond] H bond of the hydrocarbon yields a more strongly bound adduct. Combining the different conclusions, the present computational research points to the

  9. Weak bond screening system

    NASA Astrophysics Data System (ADS)

    Chuang, S. Y.; Chang, F. H.; Bell, J. R.

    Consideration is given to the development of a weak bond screening system which is based on the utilization of a high power ultrasonic (HPU) technique. The instrumentation of the prototype bond strength screening system is described, and the adhesively bonded specimens used in the system developmental effort are detailed. Test results obtained from these specimens are presented in terms of bond strength and level of high power ultrasound irradiation. The following observations were made: (1) for Al/Al specimens, 2.6 sec of HPU irradiation will screen weak bond conditions due to improper preparation of bonding surfaces; (2) for composite/composite specimens, 2.0 sec of HPU irradiation will disrupt weak bonds due to under-cured conditions; (3) for Al honeycomb core with composite skin structure, 3.5 sec of HPU irradiation will disrupt weak bonds due to bad adhesive or oils contamination of bonding surfaces; and (4) for Nomex honeycomb with Al skin structure, 1.3 sec of HPU irradiation will disrupt weak bonds due to bad adhesive.

  10. On the nature of bonding in binary Be2O2 and Si2O2 clusters: rhombic four-center four-electron π and σ bonds.

    PubMed

    Wang, Kang; Wang, Ying-Jin; Li, Da-Zhi; Ou, Ting; Zhao, Xiao-Yun; Zhai, Hua-Jin

    2016-04-14

    The structural and electronic properties and chemical bonding of binary Be2O2 and Si2O2 clusters have been studied using quantum chemical calculations at the B3LYP level. For the Be2O2 cluster, the potential energy surface is probed by unbiased structural searches and the global-minimum structure was established using the B3LYP calculations, complemented by PBE0 and single-point CCSD(T) calculations for top isomers. The perfectly planar D2h Be2O2 ((1)Ag) global minimum is well defined, being at least 3.64 eV lower in energy than alternative structures at the CCSD(T)//B3LYP/aug-cc-pVTZ level. Chemical bonding analyses show that D2h Be2O2 and Si2O2 clusters possess the rhombic four-center four-electron (4c-4e) π bond, that is, the o-bond, a conception derived from electron-deficient boron oxide clusters lately. Furthermore, the Be2O2 and Si2O2 clusters also exhibit rhombic 4c-4e σ bonds, both for the radial and tangential σ frameworks (σr and σt). The σt framework is classified as an o-bond only formally, due to the secondary contribution from the Be/Si s component. The three-fold (π, σr, and σt) o-bonds in Be2O2 and Si2O2 are considered to resemble the three-fold aromaticity in all-metal Al4(2-) dianions. A 4c-4e o-bond makes use of four O 2p electrons, which would otherwise be two lone-pairs, for a delocalized and completely bonding orbital, as well as a residual nonbonding orbital. Three-fold o-bonds thus greatly stabilize the binary Be2O2 and Si2O2 clusters. We anticipate that the bonding concept should be applicable to additional molecular systems, including those with larger heterocyclic rings. PMID:26997584

  11. Bonded semiconductor substrate

    DOEpatents

    Atwater, Jr.; Harry A. , Zahler; James M.

    2010-07-13

    Ge/Si and other nonsilicon film heterostructures are formed by hydrogen-induced exfoliation of the Ge film which is wafer bonded to a cheaper substrate, such as Si. A thin, single-crystal layer of Ge is transferred to Si substrate. The bond at the interface of the Ge/Si heterostructures is covalent to ensure good thermal contact, mechanical strength, and to enable the formation of an ohmic contact between the Si substrate and Ge layers. To accomplish this type of bond, hydrophobic wafer bonding is used, because as the invention demonstrates the hydrogen-surface-terminating species that facilitate van der Waals bonding evolves at temperatures above 600.degree. C. into covalent bonding in hydrophobically bound Ge/Si layer transferred systems.

  12. Energy pulse bonding

    NASA Technical Reports Server (NTRS)

    Smith, G. C.

    1972-01-01

    To eliminate many of the present termination problems a technique called energy pulse bonding (EPB) was developed. The process demonstrated the capability of: (1) joining conductors without prior removal of insulations, (2) joining conductors without danger of brittle intermetallics, (3) increased joint temperature capability, (4) simultaneous formation of several bonds, (5) capability of higher joint density, and (6) a production oriented process. The following metals were successfully bonded in the solid state: copper, beryllium copper, phosphor bronze, aluminum, brass, and Kovar.

  13. BONDING ALUMINUM METALS

    DOEpatents

    Noland, R.A.; Walker, D.E.

    1961-06-13

    A process is given for bonding aluminum to aluminum. Silicon powder is applied to at least one of the two surfaces of the two elements to be bonded, the two elements are assembled and rubbed against each other at room temperature whereby any oxide film is ruptured by the silicon crystals in the interface; thereafter heat and pressure are applied whereby an aluminum-silicon alloy is formed, squeezed out from the interface together with any oxide film, and the elements are bonded.

  14. Chemical bonding technology

    NASA Technical Reports Server (NTRS)

    Plueddemann, E.

    1986-01-01

    Primers employed in bonding together the various material interfaces in a photovoltaic module are being developed. The approach develops interfacial adhesion by generating actual chemical bonds between the various materials bonded together. The current status of the program is described along with the progress toward developing two general purpose primers for ethylene vinyl acetate (EVA), one for glass and metals, and another for plastic films.

  15. Valence bond entanglement entropy.

    PubMed

    Alet, Fabien; Capponi, Sylvain; Laflorencie, Nicolas; Mambrini, Matthieu

    2007-09-14

    We introduce for SU(2) quantum spin systems the valence bond entanglement entropy as a counting of valence bond spin singlets shared by two subsystems. For a large class of antiferromagnetic systems, it can be calculated in all dimensions with quantum Monte Carlo simulations in the valence bond basis. We show numerically that this quantity displays all features of the von Neumann entanglement entropy for several one-dimensional systems. For two-dimensional Heisenberg models, we find a strict area law for a valence bond solid state and multiplicative logarithmic corrections for the Néel phase. PMID:17930468

  16. High reliability bond program using small diameter aluminum wire

    NASA Technical Reports Server (NTRS)

    Macha, M.; Thiel, R. A.

    1975-01-01

    The program was undertaken to characterize the performance of small diameter aluminum wire ultrasonically bonded to conductors commonly encountered in hybrid assemblies, and to recommend guidelines for improving this performance. Wire, 25.4, 38.1 and 50.8 um (1, 1.5 and 2 mil), was used with bonding metallization consisting of thick film gold, thin film gold and aluminum as well as conventional aluminum pads on semiconductor chips. The chief tool for evaluating the performance was the double bond pull test in conjunction with a 72 hour - 150 C heat soak and -65 C to +150 C thermal cycling. In practice the thermal cycling was found to have relatively little effect compared to the heat soak. Pull strength will decrease after heat soak as a result of annealing of the aluminum wire; when bonded to thick film gold, the pull strength decreased by about 50% (weakening of the bond interface was the major cause of the reduction). Bonds to thin film gold lost about 30 - 40% of their initial pull strenth; weakening of the wire itself at the bond heel was the predominant cause. Bonds to aluminum substrate metallization lost only about 22%. Bonds between thick and thin film gold substrate metallization and semiconductor chips substantiated the previous conclusions but also showed that in about 20 to 25% of the cases, bond interface failure occurred at the semiconductor chip.

  17. Interfacial bonding stability

    NASA Technical Reports Server (NTRS)

    Boerio, J.

    1984-01-01

    Interfacial bonding stability by in situ ellipsometry was investigated. It is found that: (1) gamma MPS is an effective primer for bonding ethylene vinyl acetate (EVA) to aluminum; (2) ellipsometry is an effective in situ technique for monitoring the stability of polymer/metal interfaces; (3) the aluminized back surface of silicon wafers contain significant amounts of silicon and may have glass like properties.

  18. The dissociative bond.

    PubMed

    Gordon, Nirit

    2013-01-01

    Dissociation leaves a psychic void and a lingering sense of psychic absence. How do 2 people bond while they are both suffering from dissociation? The author explores the notion of a dissociative bond that occurs in the aftermath of trauma--a bond that holds at its core an understanding and shared detachment from the self. Such a bond is confined to unspoken terms that are established in the relational unconscious. The author proposes understanding the dissociative bond as a transitional space that may not lead to full integration of dissociated knowledge yet offers some healing. This is exemplified by R. Prince's (2009) clinical case study. A relational perspective is adopted, focusing on the intersubjective aspects of a dyadic relationship. In the dissociative bond, recognition of the need to experience mutual dissociation can accommodate a psychic state that yearns for relationship when the psyche cannot fully confront past wounds. Such a bond speaks to the need to reestablish a sense of human relatedness and connection when both parties in the relationship suffer from disconnection. This bond is bound to a silence that becomes both a means of protection against the horror of traumatic memory and a way to convey unspoken gestures toward the other. PMID:23282044

  19. Chemical Bonds I

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    Chemical bonding is discussed from a bond energy, rather than a wave mechanics, viewpoint. This approach is considered to be more suitable for the average student. (The second part of the article will appear in a later issue of the journal.) (AL)

  20. Earth-Bonding.

    ERIC Educational Resources Information Center

    Norgaard, Jim

    1988-01-01

    Defines "earth bonding" as dynamic interaction between individual and physical environment. Examines methods and goals of traditional environmental education. Describes development of five-day camping workshop for 11 outdoor education teachers. Describes how workshop facilitated earth bonding for teachers. Calls for further research in "bonding…

  1. Shape Bonding method

    NASA Technical Reports Server (NTRS)

    Pontius, James T. (Inventor)

    2010-01-01

    The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.

  2. Halogen bonding anion recognition.

    PubMed

    Brown, Asha; Beer, Paul D

    2016-07-01

    A halogen bond is an attractive non-covalent interaction between an electrophilic region in a covalently bonded halogen atom and a Lewis base. While these interactions have long been exploited as a tool in crystal engineering their powerful ability to direct supramolecular self-assembly and molecular recognition processes in solution has, until recently, been overlooked. During the last decade however an ever-increasing number of studies on solution-phase halogen-bond-mediated anion recognition processes has emerged. This Feature Article summarises advancements which have been made thus far in this rapidly developing research area. We survey the use of iodoperfluoroarene, haloimidazolium and halotriazole/triazolium halogen-bond-donor motifs in anion receptor design, before providing an account of our research into the application of mechanically interlocked rotaxane and catenane frameworks as halogen bonding anion host systems. PMID:27273600

  3. Ultrasonically bonded value assembly

    NASA Technical Reports Server (NTRS)

    Salvinski, R. J. (Inventor)

    1975-01-01

    A valve apparatus capable of maintaining a fluid-tight seal over a relatively long period of time by releasably bonding a valve member to its seat is described. The valve member is bonded or welded to the seat and then released by the application of the same energy to the bond joint. The valve member is held in place during the bonding by a clamping device. An appropriate force device can activate the opening and closing of the valve member. Various combinations of material for the valve member and valve seat can be utilized to provide an adequate sealing bond. Aluminum oxide, stainless steel, inconel, tungsten carbide as hard materials and copper, aluminum, titanium, silver, and gold as soft materials are suggested.

  4. Wood Bond Testing

    NASA Technical Reports Server (NTRS)

    1989-01-01

    A joint development program between Hartford Steam Boiler Inspection Technologies and The Weyerhaeuser Company resulted in an internal bond analyzer (IBA), a device which combines ultrasonics with acoustic emission testing techniques. It is actually a spinoff from a spinoff, stemming from a NASA Lewis invented acousto-ultrasonic technique that became a system for testing bond strength of composite materials. Hartford's parent company, Acoustic Emission Technology Corporation (AET) refined and commercialized the technology. The IBA builds on the original system and incorporates on-line process control systems. The IBA determines bond strength by measuring changes in pulsar ultrasonic waves injected into a board. Analysis of the wave determines the average internal bond strength for the panel. Results are displayed immediately. Using the system, a mill operator can adjust resin/wood proportion, reduce setup time and waste, produce internal bonds of a consistent quality and automatically mark deficient products.

  5. Bonding in elemental boron: a view from electronic structure calculations using maximally localized Wannier functions

    NASA Astrophysics Data System (ADS)

    Ogitsu, Tadashi; Gygi, Francois; Reed, John; Schwegler, Eric; Galli, Giulia

    2007-03-01

    Boron exhibits the most complex structure of all elemental solids, with more than 300 atoms per unit cell arranged in interconnecting icosahedra, and some crystallographic positions occupied with a probability of less than one. The precise determination of the ground state geometry of boron---the so-called β-boron structure--has been elusive and its electronic and bonding properties have been difficult to rationalize. Using lattice model Monte Carlo optimization techniques and ab-initio simulations, we have shown that a defective, quasi-ordered β solid is the most stable structure at zero as well as finite T. In the absence of partially occupied sites (POS), the perfect β-boron crystal is unstable; the presence of POS lower its internal energy below that of an ordered α-phase, not mere an entropic effect. We present a picture of the intricate and unique bonding in boron based on maximally localized Wannier (MLWF) functions, which indicates that the presence of POS provides a subtle, yet essential spatial balance between electron deficient and fully saturated bonds. This work was performed under the auspices of the U.S. Dept. of Energy at the University of California/ LLNL under contract no. W-7405-Eng-48.

  6. Reactions involving shifting of the double bond in cyclic ethers

    SciTech Connect

    Ibatullin, U.G.; Petrushina, T.F.; Akhmadeeva, A.A.; Safarov, M.G.

    1985-09-01

    4-Methylenetetrahydropyran undergoes isomerization to 4-methyl-5,6-dihydropyran in the presence of sodium on aluminum oxide. Both pyrans are converted to a vinyl ether, viz., 4-methyl-2,3-dihydropyran, under the influence of iron pentacarbonyl.

  7. Free Radical Addition of Butanethiol to Vegetable Oil Double Bonds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Butanethiol was used in ultraviolet-initiated thiol-ene reaction with canola and corn oils to produce sulfide modified vegetable oils (SMVO). The crude SMVO product was successfully purified by solvent extraction, vacuum evaporation and silica gel chromatography. The SMVO products were characteriz...

  8. Double-bond defect modelling in As-S glasses

    NASA Astrophysics Data System (ADS)

    Boyko, V.; Shpotyuk, O.; Hyla, M.

    2010-11-01

    Ab initio calculations with the RHF/6-311G* basis set are used for geometrical optimization of regular pyramidal and defect quasi-tetrahedral clusters in binary As-S glasses. It is shown that quasi-tetrahedral S=AsS3/2 structural units are impossible as main network-building blocks in these glasses.

  9. Seeing Double

    NASA Astrophysics Data System (ADS)

    Pesic, Peter

    2003-10-01

    The separateness and connection of individuals is perhaps the central question of human life: What, exactly, is my individuality? To what degree is it unique? To what degree can it be shared, and how? To the many philosophical and literary speculations about these topics over time, modern science has added the curious twist of quantum theory, which requires that the elementary particles of which everything consists have no individuality at all. All aspects of chemistry depend on this lack of individuality, as do many branches of physics. From where, then, does our individuality come? In Seeing Double, Peter Pesic invites readers to explore this intriguing set of questions. He draws on literary and historical examples that open the mind (from Homer to Martin Guerre to Kafka), philosophical analyses that have helped to make our thinking and speech more precise, and scientific work that has enabled us to characterize the phenomena of nature. Though he does not try to be all-inclusive, Pesic presents a broad range of ideas, building toward a specific point of view: that the crux of modern quantum theory is its clash with our ordinary concept of individuality. This represents a departure from the usual understanding of quantum theory. Pesic argues that what is bizarre about quantum theory becomes more intelligible as we reconsider what we mean by individuality and identity in ordinary experience. In turn, quantum identity opens a new perspective on us. Peter Pesic is a Tutor and Musician-in-Residence at St. John's College, Santa Fe, New Mexico. He has a Ph.D. in physics from Stanford University.

  10. Double inflation

    SciTech Connect

    Silk, J.; Turner, M.S.

    1986-04-01

    The Zel'dovich spectrum of adiabatic density perturbations is a generic prediction of inflation. There is increasing evidence that when the spectrum is normalized by observational data on small scales, there is not enough power on large scales to account for the observed large-scale structure in the Universe. Decoupling the spectrum on large and small scales could solve this problem. As a means of decoupling the large and small scales we propose double inflation (i.e., two episodes of inflation). In this scenario the spectrum on large scales is determined by the first episode of inflation and those on small scales by a second episode of inflation. We present three models for such a scenario. By nearly saturating the large angular-scale cosmic microwave anisotropy bound, we can easily account for the observed large-scale structure. We take the perturbations on small scales to be very large, deltarho/rho approx. = 0.1 to 0.01, which results in the production of primordial black holes (PBHs), early formation of structure, reionization of the Universe, and a rich array of astrophysical events. The ..cap omega..-problem is also addressed by our scenario. Allowing the density perturbations produced by the second episode of inflation to be large also lessens the fine-tuning required in the scalar potential and makes reheating much easier. We briefly speculate on the possibility that the second episode of inflation proceeds through the nucleation of bubbles, which today manifest themselves as empty bubbles whose surfaces are covered with galaxies. 37 refs., 1 fig.

  11. Bonding and Geometry of OCF(3)(-), ONF(3), and Related Molecules in Terms of the Ligand Close Packing Model.

    PubMed

    Gillespie, Ronald J.; Robinson, Edward A.; Heard, George L.

    1998-12-28

    The nature of the bonding in OCF(3)(-) and the isoelectronic molecule ONF(3) has been the subject of much discussion for many years, because these species appear to have unusual bond lengths and angles. We have reinvestigated the nature of the bonding in these and some related molecules by analyzing their calculated electron density distributions. The results show that the bonding in the series OBF(3)(2)(-), OCF(3)(-), ONF(3) ranges from predominately ionic in OBF(3)(2)(-) to predominately covalent in ONF(3) and that the interligand distances are consistent with the close packing of the ligands around the central atom. The AO bonds (A = B, C, N) are double bonds ranging in nature from a very ionic B=O bond to a predominately covalent N=O double bond, but all three are strong and short so that, in accordance with the ligand close packing (LCP) model, the AF bonds are correspondingly long. Also consistent with this model the bonds in a three-coordinated AOF(2) molecule are shorter than those in the corresponding AOF(3) molecule. Protonation of the doubly bonded oxygen, which converts the A=O bond to a single A-OH bond in each case, considerably lengthens the A-O bond, and the bond angles accordingly adopt values much closer to the tetrahedral angle. The difficulties of trying to describe the bonding in these molecules in terms of Lewis structures are discussed. PMID:11670825

  12. The Halogen Bond

    PubMed Central

    2016-01-01

    The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185

  13. The Halogen Bond.

    PubMed

    Cavallo, Gabriella; Metrangolo, Pierangelo; Milani, Roberto; Pilati, Tullio; Priimagi, Arri; Resnati, Giuseppe; Terraneo, Giancarlo

    2016-02-24

    The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185

  14. Instability of bell-shaped solitary waves in a two-component hydrogen-bonded chain

    NASA Astrophysics Data System (ADS)

    Machnikowski, Paweł; Radosz, Andrzej

    1998-06-01

    Bell-shaped solitons found in a chain of asymmetric double-well hydrogen bonds are unstable, unlike ordinary solitons or kinks. A proof of their instability for low velocities based on a perturbation approach is proposed.

  15. Detecting Defective Solder Bonds

    NASA Technical Reports Server (NTRS)

    Paulson, R.; Barney, J.; Decker, H. J.

    1984-01-01

    Method is noncontact and nondestructive. Technique detects solder bonds in solar array of other large circuit board, using thermal-imaging camera. Board placed between heat lamp and camera. Poor joints indiated by "cold" spots on the infrared image.

  16. The Nature of Activated Non-classical Hydrogen Bonds: A Case Study on Acetylcholinesterase-Ligand Complexes.

    PubMed

    Berg, Lotta; Mishra, Brijesh Kumar; Andersson, C David; Ekström, Fredrik; Linusson, Anna

    2016-02-18

    Molecular recognition events in biological systems are driven by non-covalent interactions between interacting species. Here, we have studied hydrogen bonds of the CH⋅⋅⋅Y type involving electron-deficient CH donors using dispersion-corrected density functional theory (DFT) calculations applied to acetylcholinesterase-ligand complexes. The strengths of CH⋅⋅⋅Y interactions activated by a proximal cation were considerably strong; comparable to or greater than those of classical hydrogen bonds. Significant differences in the energetic components compared to classical hydrogen bonds and non-activated CH⋅⋅⋅Y interactions were observed. Comparison between DFT and molecular mechanics calculations showed that common force fields could not reproduce the interaction energy values of the studied hydrogen bonds. The presented results highlight the importance of considering CH⋅⋅⋅Y interactions when analysing protein-ligand complexes, call for a review of current force fields, and opens up possibilities for the development of improved design tools for drug discovery. PMID:26751405

  17. Intrinsic bond strength of metal films on polymer substrates

    NASA Technical Reports Server (NTRS)

    Wheeler, Donald R.; Osaki, Hiroyuki

    1990-01-01

    A semiquantitative method for the measurement of the intrinsic bond strength between elastic substrates and elastic films that fail by brittle fracture is described. Measurements on a polyethylene terephthalate (PET)-Ni couple were used to verify the essential features of the analysis. It was found that the interfacial shear strength of Ni on PET doubled after ion etching.

  18. 27 CFR 24.147 - Operations bond or unit bond.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Operations bond or unit bond. 24.147 Section 24.147 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS WINE Establishment and Operations Bonds and Consents of Surety § 24.147 Operations bond or unit...

  19. Structure and Bonding in Group 14 Congeners of Ethene: DFT Calculations in the Inorganic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Streit, Bennett R.; Geiger, David K.

    2005-01-01

    A computational experiment is devised for advanced inorganic laboratory course that allows the students to explore the structure and bonding patterns of ethene and some heavier analogues. The HOMO-LUMO gaps, double bond dissociation energetics, and optimized geometries of ethene, disilene, and digermene are explored.

  20. Urethane/Silicone Adhesives for Bonding Flexing Metal Parts

    NASA Technical Reports Server (NTRS)

    Edwards, Paul D.

    2004-01-01

    Adhesives that are blends of commercially available urethane and silicone adhesives have been found to be useful for bonding metal parts that flex somewhat during use. These urethane/silicone adhesives are formulated for the specific metal parts to be bonded. The bonds formed by these adhesives have peel and shear strengths greater than those of bonds formed by double-sided tapes and by other adhesives, including epoxies and neat silicones. In addition, unlike the bonds formed by epoxies, the bonds formed by these adhesives retain flexibility. In the initial application for which the urethane/silicone adhesives were devised, there was a need to bond spring rings, which provide longitudinal rigidity for inflatable satellite booms, with the blades that provide the booms axial strength. The problem was to make the bonds withstand the stresses, associated with differences in curvature between the bonded parts, that arose when the booms were deflated and the springs were compressed. In experiments using single adhesives (that is, not the urethane/ silicone blends), the bonds were broken and, in each experiment, it was found that the adhesive bonded well with either the ring or with the blade, but not both. After numerous experiments, the adhesive that bonded best with the rings and the adhesive that bonded best with the blades were identified. These adhesives were then blended and, as expected, the blend bonded well with both the rings and the blades. The two adhesives are Kalex (or equivalent) high-shear-strength urethane and Dow Corning 732 (or equivalent) silicone. The nominal mixture ratio is 5 volume parts of the urethane per 1 volume part of the silicone. Increasing the proportion of silicone makes the bond weaker but more flexible, and decreasing the proportion of silicone makes the bond stronger but more brittle. The urethane/silicone blend must be prepared and used quickly because of the limited working time of the urethane: The precursor of the urethane

  1. Strength of Chemical Bonds

    NASA Technical Reports Server (NTRS)

    Christian, Jerry D.

    1973-01-01

    Students are not generally made aware of the extraordinary magnitude of the strengths of chemical bonds in terms of the forces required to pull them apart. Molecular bonds are usually considered in terms of the energies required to break them, and we are not astonished at the values encountered. For example, the Cl2 bond energy, 57.00 kcal/mole, amounts to only 9.46 x 10(sup -20) cal/molecule, a very small amount of energy, indeed, and impossible to measure directly. However, the forces involved in realizing the energy when breaking the bond operate over a very small distance, only 2.94 A, and, thus, f(sub ave) approx. equals De/(r - r(sub e)) must be very large. The forces involved in dissociating the molecule are discussed in the following. In consideration of average forces, the molecule shall be assumed arbitrarily to be dissociated when the atoms are far enough separated so that the potential, relative to that of the infinitely separated atoms, is reduced by 99.5% from the potential of the molecule at the equilibrium bond length (r(sub e)) for Cl2 of 1.988 A this occurs at 4.928 A.

  2. Asymmetric bifurcated halogen bonds.

    PubMed

    Novák, Martin; Foroutan-Nejad, Cina; Marek, Radek

    2015-03-01

    Halogen bonding (XB) is being extensively explored for its potential use in advanced materials and drug design. Despite significant progress in describing this interaction by theoretical and experimental methods, the chemical nature remains somewhat elusive, and it seems to vary with the selected system. In this work we present a detailed DFT analysis of three-center asymmetric halogen bond (XB) formed between dihalogen molecules and variously 4-substituted 1,2-dimethoxybenzene. The energy decomposition, orbital, and electron density analyses suggest that the contribution of electrostatic stabilization is comparable with that of non-electrostatic factors. Both terms increase parallel with increasing negative charge of the electron donor molecule in our model systems. Depending on the orientation of the dihalogen molecules, this bifurcated interaction may be classified as 'σ-hole - lone pair' or 'σ-hole - π' halogen bonds. Arrangement of the XB investigated here deviates significantly from a recent IUPAC definition of XB and, in analogy to the hydrogen bonding, the term bifurcated halogen bond (BXB) seems to be appropriate for this type of interaction. PMID:25656525

  3. Analysis of adhesively bonded composite lap joints

    SciTech Connect

    Tong, L.; Kuruppu, M.; Kelly, D.

    1994-12-31

    A new nonlinear formulation is developed for the governing equations for the shear and peel stresses in adhesively bonded composite double lap joints. The new formulation allows arbitrary nonlinear stress-strain characteristics in both shear and peel behavior. The equations are numerically integrated using a shooting technique and Newton-Raphson method behind a user friendly interface. The failure loads are predicted by utilizing the maximum stress criterion, interlaminar delamination and the energy density failure criteria. Numerical examples are presented to demonstrate the effect of the nonlinear adhesive behavior on the stress distribution and predict the failure load and the associated mode.

  4. Surface analysis in composite bonding

    NASA Technical Reports Server (NTRS)

    Messick, D. L.; Wightman, J. P.

    1982-01-01

    The role of the interfacial region in determining the bond strength and durability of composite bonds is discussed. The characterization of a variety of carbon fibers including Celion 6000 using both scanning electron microscopy and X-ray photoelectron spectroscopy is discussed. The emphasis is on composite bonding, that is, the adhesive bonding between composites in contrast to fiber-matrix interaction. The primary objective of the research is the characterization of composite surfaces before adhesive bonding and after fracture of bonded specimens. Work done on the analysis of composite samples pretreated in a number of ways prior to bonding is detailed.

  5. Insulation bonding test system

    NASA Technical Reports Server (NTRS)

    Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (Inventor)

    1984-01-01

    A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.

  6. Metallic Adhesion and Bonding

    NASA Technical Reports Server (NTRS)

    Ferrante, J.; Smith, J. R.; Rose, J. H.

    1984-01-01

    Although metallic adhesion has played a central part in much tribological speculation, few quantitative theoretical calculations are available. This is in part because of the difficulties involved in such calculations and in part because the theoretical physics community is not particularly involved with tribology. The calculations currently involved in metallic adhesion are summarized and shown that these can be generalized into a scaled universal relationship. Relationships exist to other types of covalent bonding, such as cohesive, chemisorptive, and molecular bonding. A simple relationship between surface energy and cohesive energy is offered.

  7. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... bonding. 2580.412-20 Section 2580.412-20 Labor Regulations Relating to Labor (Continued) EMPLOYEE BENEFITS SECURITY ADMINISTRATION, DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580.412-20 Use of existing...

  8. SHM system using rectangular versus circular piezoceramic for the inspection within the bond of a composite bonded joint

    NASA Astrophysics Data System (ADS)

    Quaegebeur, Nicolas; Micheau, Philippe; Masson, Patrice; Castaings, Michel

    2012-04-01

    A bonded joint between an aluminum plate and CFRP plate (7 plies) is considered using a titanium spar. The bonding is ensured by double sided adhesive that is prone to degradation with aging structures. The problem is to detect the disbond occurring at the CFRP plate/titanium spar interface using guided waves generated by piezoceramic transducers (PZT) bonded on the CFRP plate. The objective of the present work is to optimize the SHM configuration (PZT location, Lamb wave mode, size and shape of the PZT) for pitch and catch measurements within the bond. 1D, 2D and 3D numerical simulations of the instrumented structure were performed to optimize the SHM configuration. It appears that the rectangular shape can ensure a plane wave front within the bond, since the circular shape generates complex wave fronts. For experimental investigation, coupon structure was manufactured with synthetic damages inserted using two hemispherical Teflon tapes between adhesive and titanium spar. The structure was instrumented for inspection within the bond by using rectangular PZT. Experimental validation of propagation characteristics and damage sensitivity are performed using LDV measurement within the bond line. Damage detectability using rectangular piezoceramics in pitch-catch configuration within the bond is validated.

  9. Advanced double layer capacitors

    NASA Technical Reports Server (NTRS)

    Sarangapani, S.; Lessner, P.; Forchione, J.; Laconti, A. B.

    1989-01-01

    There is a need for large amounts of power to be delivered rapidly in a number of airborne and space systems. Conventional, portable power sources, such as batteries, are not suited to delivering high peak power pulses. The charge stored at the electrode-electrolyte double layer is, however, much more assessible on a short time scale. Devices exploiting this concept were fabricated using carbon and metal oxides (Pinnacle Research) as the electrodes and sulfuric acid as the electrolyte. The approach reported, replaces the liquid sulfuric acid electrolyte with a solid ionomer electrolyte. The challenge is to form a solid electrode-solid ionomer electrolyte composite which has a high capacitance per geometric area. The approach to maximize contact between the electrode particles and the ionomer was to impregnate the electrode particles using a liquid ionomer solution and to bond the solvent-free structure to a solid ionomer membrane. Ruthenium dioxide is the electrode material used. Three strategies are being pursued to provide for a high area electrode-ionomer contact: mixing of the RuOx with a small volume of ionomer solution followed by filtration to remove the solvent, and impregnation of the ionomer into an already formed RuOx electrode. RuOx powder and electrodes were examined by non-electrochemical techniques. X-ray diffraction has shown that the material is almost pure RuO2. The electrode structure depends on the processing technique used to introduce the Nafion. Impregnated electrodes have Nafion concentrated near the surface. Electrodes prepared by the evaporation method show large aggregates of crystals surrounded by Nafion.

  10. Bonding without Tears.

    ERIC Educational Resources Information Center

    Akeroyd, F. Michael

    1982-01-01

    Discusses merits of using sigma-pi model of ethylene as a teaching aid in introductory organic chemistry. The nonmathematical treatment of sigma-pi bonding is then extended to such phenomena as conjugation, hyperconjugation, Markovnikoff addition, aromaticity, and aromatic substitution. (SK)

  11. GRAPHITE BONDING METHOD

    DOEpatents

    King, L.D.P.

    1964-02-25

    A process for bonding or joining graphite members together in which a thin platinum foil is placed between the members, heated in an inert atmosphere to a temperature of 1800 deg C, and then cooled to room temperature is described. (AEC)

  12. Flax Fiber - Interfacial Bonding

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measured flax fiber physical and chemical properties potentially impact bonding and thus stress transfer between the matrix and fiber within composites. These first attempts at correlating flax fiber quality and biofiber composites contain the initial steps towards identifying key flax fiber charac...

  13. Bonds Between Atoms.

    ERIC Educational Resources Information Center

    Holden, Alan

    The field of inquiry into how atoms are bonded together to form molecules and solids crosses the borderlines between physics and chemistry encompassing methods characteristic of both sciences. At one extreme, the inquiry is pursued with care and rigor into the simplest cases; at the other extreme, suggestions derived from the more careful inquiry…

  14. Photochemical tissue bonding

    DOEpatents

    Redmond, Robert W.; Kochevar, Irene E.

    2012-01-10

    Photochemical tissue bonding methods include the application of a photosensitizer to a tissue and/or tissue graft, followed by irradiation with electromagnetic energy to produce a tissue seal. The methods are useful for tissue adhesion, such as in wound closure, tissue grafting, skin grafting, musculoskeletal tissue repair, ligament or tendon repair and corneal repair.

  15. A double-double/double-single computation package

    SciTech Connect

    Bailey, David H.

    2004-12-01

    The DDFUNIDSFUN software permits a new or existing Fortran-90 program to utilize double-double precision (approx. 31 digits) or double-single precision (approx. 14 digits) arithmetic. Double-double precision is required by a rapidly expandirtg body of scientific computations in physics and mathematics, for which the conventional 64-bit IEEE computer arithmetic (about 16 decimal digit accuracy) is not sufficient. Double-single precision permits users of systems that do not have hardware 64-bit IEEE arithmetic (such as some game systems) to perform arithmetic at a precision nearly as high as that of systems that do. Both packages run significantly faster Than using multiple precision or arbitrary precision software for this purpose. The package includes an extensive set of low-level routines to perform high-precision arithmetic, including routines to calculate various algebraic and transcendental functions, such as square roots, sin, ccc, exp, log and others. In addition, the package includes high-level translation facilities, so that Fortran programs can utilize these facilities by making only a few changes to conventional Fortran programs. In most cases, the only changes that are required are to change the type statements of variables that one wishes to be treated as multiple precision, plus a few other minor changes. The DDFUN package is similar in functionality to the double-double part of the GD package, which was previously written at LBNL. However, the DDFUN package is written exclusively in Fortran-90, thus avoidIng difficulties that some users experience when using GD, which includes both Fortran-90 and C++ code.

  16. A double-double/double-single computation package

    Energy Science and Technology Software Center (ESTSC)

    2004-12-01

    The DDFUNIDSFUN software permits a new or existing Fortran-90 program to utilize double-double precision (approx. 31 digits) or double-single precision (approx. 14 digits) arithmetic. Double-double precision is required by a rapidly expandirtg body of scientific computations in physics and mathematics, for which the conventional 64-bit IEEE computer arithmetic (about 16 decimal digit accuracy) is not sufficient. Double-single precision permits users of systems that do not have hardware 64-bit IEEE arithmetic (such as some game systems)more » to perform arithmetic at a precision nearly as high as that of systems that do. Both packages run significantly faster Than using multiple precision or arbitrary precision software for this purpose. The package includes an extensive set of low-level routines to perform high-precision arithmetic, including routines to calculate various algebraic and transcendental functions, such as square roots, sin, ccc, exp, log and others. In addition, the package includes high-level translation facilities, so that Fortran programs can utilize these facilities by making only a few changes to conventional Fortran programs. In most cases, the only changes that are required are to change the type statements of variables that one wishes to be treated as multiple precision, plus a few other minor changes. The DDFUN package is similar in functionality to the double-double part of the GD package, which was previously written at LBNL. However, the DDFUN package is written exclusively in Fortran-90, thus avoidIng difficulties that some users experience when using GD, which includes both Fortran-90 and C++ code.« less

  17. Further developments in gold-stud bump bonding

    NASA Astrophysics Data System (ADS)

    Neher, C.; Lander, R. L.; Moskaleva, A.; Pasner, J.; Tripathi, M.; Woods, M.

    2012-02-01

    As silicon detectors in high energy physics experiments require increasingly complex assembly procedures, the availability of a wide variety of interconnect technologies provides more options for overcoming obstacles in generic R&D. Gold ball bonding has been a staple in the interconnect industry due to its ease of use and reliability. However, due to some limitations in the standard technique, alternate methods of gold-stud bonding are being developed. This paper presents recent progress and challenges faced in the development of double gold-stud bonding and 0.5 mil wire gold-stud bonding at the UC Davis Facility for Interconnect Technology. Advantages and limitations of each technique are analyzed to provide insight into potential applications for each method. Optimization of procedures and parameters is also presented.

  18. Dual resin bonded joints in polyetheretherketone (PEEK) matrix composites

    NASA Astrophysics Data System (ADS)

    Zelenak, Steve; Radford, Donald W.; Dean, Michael W.

    1993-04-01

    The paper describes applications of the dual resin (miscible polymer) bonding technique (Smiley, 1989) developed as an alternative to traditional bonding approaches to joining thermoplastic matrix composite subassemblies into structures. In the experiments, the performance of joint geometries, such as those that could be used to assemble large truss structures in space, are investigated using truss joint models consisting of woven carbon fiber/PEEK tubes of about 1 mm wall thickness. Specific process conditions and hand-held hardware used to apply heat and pressure were chosen to simulate a field asembly technique. Results are presented on tube/cruciform double lap shear tests, pinned-pinned tube compression tests, and single lap shear bond tests of joints obtained using the dual resin bonding technique.

  19. Athermal fracture of covalent bonds

    SciTech Connect

    Gilman, J.J.

    1999-08-01

    Most fracture is athermal. Either because it occurs at low temperatures or because it occurs too fast for thermal activation to be effective. Thus it must be directly activated by applied stresses. This can occur via quantum tunneling when the chemical bonding of a solid resides in localized (covalent) bonds. Then applied stresses can cause the bonding electrons to become delocalized (anti-bonded) through quantum tunneling. That is, the bonds become broken. The process is related to the Zener tunneling process that is thought to be responsible for dielectric breakdown in semiconductors. Under a driving force, bonding electrons tunnel at constant energy from their bonding states into anti-bonding states through the forbidden gap in the bonding energy spectrum.

  20. Palladium- and Copper-Catalyzed Arylation of Carbon-Hydrogen Bonds

    PubMed Central

    Daugulis, Olafs; Do, Hien-Quang; Shabashov, Dmitry

    2010-01-01

    The transition-metal-catalyzed functionalization of C-H bonds is a powerful method for generating carbon-carbon bonds. Although significant advances to this field have been reported during the last decade, many challenges remain. First, most of the methods are substrate-specific and thus cannot be generalized. Second, conversions of unactivated (i.e. not benzylic or alpha to heteroatom) sp3 C–H bonds to C–C bonds are rare, with most examples limited to t-butyl groups—a conversion that is inherently simple because there are no β-hydrogens that can be eliminated. Finally, the palladium, rhodium, and ruthenium catalysts routinely used for the conversion of C–H bonds to C–C bonds are expensive. Catalytically active metals that are cheaper and less exotic (e.g. copper, iron, and manganese) are rarely used. This Account describes our attempts to provide solutions to these three problems. We have developed a general method for directing-group-containing arene arylation by aryl iodides. Using palladium acetate as the catalyst, we arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions. We have also developed a method for the palladium-catalyzed auxiliary-assisted arylation of unactivated sp3 C–H bonds. This procedure allows for the β-arylation of carboxylic acid derivatives and the γ-arylation of amine derivatives. Furthermore, copper catalysis can be used to mediate the arylation of acidic arene C–H bonds (i.e. those with pKa values <35 in DMSO). Using a copper iodide catalyst in combination with a base and a phenanthroline ligand, we successfully arylated electron-rich and electron-deficient heterocycles and electron-poor arenes possessing at least two electron-withdrawing groups. The reaction exhibits unusual regioselectivity: arylation occurs at the most hindered position. This copper-catalyzed method supplements the well-known C–H activation/borylation methodology, in which

  1. The Cambridge Double Star Atlas

    NASA Astrophysics Data System (ADS)

    MacEvoy, Bruce; Tirion, Wil

    2015-12-01

    Preface; What are double stars?; The binary orbit; Double star dynamics; Stellar mass and the binary life cycle; The double star population; Detecting double stars; Double star catalogs; Telescope optics; Preparing to observe; Helpful accessories; Viewing challenges; Next steps; Appendices: target list; Useful formulas; Double star orbits; Double star catalogs; The Greek alphabet.

  2. Double outlet right ventricle

    MedlinePlus

    ... medlineplus.gov/ency/article/007328.htm Double outlet right ventricle To use the sharing features on this page, please enable JavaScript. Double outlet right ventricle (DORV) is a heart disease that is ...

  3. Chromosome doubling method

    DOEpatents

    Kato, Akio

    2006-11-14

    The invention provides methods for chromosome doubling in plants. The technique overcomes the low yields of doubled progeny associated with the use of prior techniques for doubling chromosomes in plants such as grasses. The technique can be used in large scale applications and has been demonstrated to be highly effective in maize. Following treatment in accordance with the invention, plants remain amenable to self fertilization, thereby allowing the efficient isolation of doubled progeny plants.

  4. Double Potoionization of Molecular Hydrogen

    NASA Astrophysics Data System (ADS)

    Vanroose, Wim

    2006-05-01

    We report a complete numerical solution of the Schr"odinger equation for the double photoionization of H2, a process where a single photon emits two electrons. The results suggest that the distribution of photoelectrons emitted from aligned molecules reflects electron correlation effects that are purely molecular in origin. It confirms recent experimental results in experiments on oriented hydrogen molecules. These experiments observed that the ejection pattern of the electrons depends sensitively on the bond distance between the two nuclei as well as the orientation with respect to the polarization of the photon. We give an overview of the numerical methods we used to solve the exact Schrodinger equation for this problem. We also discuss the different molecular effect we observe in our calculations and compare with experimental observations

  5. Transition-Metal-Catalyzed Redox-Neutral and Redox-Green C-H Bond Functionalization.

    PubMed

    Wang, Hongli; Huang, Hanmin

    2016-08-01

    Transition-metal-catalyzed C-H bond functionalization has become one of the most promising strategies to prepare complex molecules from simple precursors. However, the utilization of environmentally unfriendly oxidants in the oxidative C-H bond functionalization reactions reduces their potential applications in organic synthesis. This account describes our recent efforts in the development of a redox-neutral C-H bond functionalization strategy for direct addition of inert C-H bonds to unsaturated double bonds and a redox-green C-H bond functionalization strategy for realization of oxidative C-H functionalization with O2 as the sole oxidant, aiming to circumvent the problems posed by utilizing environmentally unfriendly oxidants. In principle, these redox-neutral and redox-green strategies pave the way for establishing new environmentally benign transition-metal-catalyzed C-H bond functionalization strategies. PMID:27258190

  6. C2 in a Box: Determining Its Intrinsic Bond Strength for the X(1) Σg (+) Ground State.

    PubMed

    Zou, Wenli; Cremer, Dieter

    2016-03-14

    The intrinsic bond strength of C2 in its (1) Σg (+) ground state is determined from its stretching force constant utilizing MR-CISD+Q(8,8), MR-AQCC(8,8), and single-determinant coupled cluster calculations with triple and quadruple excitations. By referencing the CC stretching force constant to its local counterparts of ethane, ethylene, and acetylene, an intrinsic bond strength half way between that of a double bond and a triple bond is obtained. Diabatic MR-CISD+Q results do not change this. Confinement of C2 and suitable reference molecules in a noble gas cage leads to compression, polarization, and charge transfer effects, which are quantified by the local CC stretching force constants and differences of correlated electron densities. These results are in line with two π bonds and a partial σ bond. Bond orders and bond dissociation energies of small hydrocarbons do not support quadruple bonding in C2 . PMID:26742466

  7. 27 CFR 24.147 - Operations bond or unit bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... amended, give an operations bond or unit bond in accordance with the applicable provisions of 27 CFR part... or contiguous distilled spirits plant qualified under 27 CFR part 19 for the production of distilled... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Operations bond or...

  8. 30 CFR 281.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 281.33 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF... a surety or personal bond to guarantee payment of a deferred portion of the bid. Upon the payment of the full amount of the cash bonus bid, the lessee's bond will be released. (b) All bonds to...

  9. 27 CFR 24.147 - Operations bond or unit bond.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... or contiguous distilled spirits plant qualified under 27 CFR part 19 for the production of distilled... amended, give an operations bond or unit bond in accordance with the applicable provisions of 27 CFR part... BUREAU, DEPARTMENT OF THE TREASURY LIQUORS WINE Establishment and Operations Bonds and Consents of...

  10. Electron density, exchange-correlation density, and bond characterization from the perspective of the valence-bond theory. II. Numerical results

    NASA Astrophysics Data System (ADS)

    Rincón, Luis; Alvarellos, J. E.; Almeida, Rafael

    2005-06-01

    In this work we have analyzed the bond character of a series of representative diatomic molecules, using valence bond and the atoms in molecules points of view. This is done using generalized valence-bond calculations. We have also employed more exigent levels, as configuration interaction with single and double excitations and complete active space self-consistent field calculations, in order to validate the generalized valence-bond results. We have explored the possibility that the known delocalization index, and a parameter that measures the excess or defect population within a given atomic basin, can be considered as indicators of the character of bond interaction. We conclude that for a proper description of the bond character, the global behavior of both the charge and two-electron densities should be considered.

  11. Combined effect of chemical pressure and valence electron concentration through the electron-deficient Li substitution on the RE4LiGe4 (RE=La, Ce, Pr, and Sm) system

    NASA Astrophysics Data System (ADS)

    Nam, Gnu; Jeon, Jieun; Kim, Youngjo; Kwon Kang, Sung; Ahn, Kyunghan; You, Tae-Soo

    2013-09-01

    Four members of the RE4LiGe4 (RE=La, Ce, Pr, and Sm) system have been prepared by high-temperature reaction method and characterized by X-ray diffractions. All compounds crystallize in the orthorhombic Gd5Si4-type structure (space group Pnma, Pearson code oP16) with bonding interactions for interslab Ge2 dimers. The Li substitution for rare-earth elements in the RE4LiGe4 system leads to a combined effect of the increased chemical pressure and the decreased valance electron concentration (VEC), which eventually results in the structure transformation from the Sm5Ge4-type with all broken interslab Ge-Ge bond for the parental RE5Ge4 to the Gd5Si4-type structure for the ternary RE4LiGe4 (RE=La, Ce, Pr, and Sm) system. Site-preference between rare-earth metals and Li is proven to generate energetically the most favorable atomic arrangements according to coloring-problem, and the rationale is provided using both the size-factor and the electronic-factor related, respectively, to site-volume and electronegativity as well as QVAL values. Tight-binding, linear-muffin-tin-orbital (TB-LMTO) calculations are performed to investigate electronic densities of states (DOS) and crystal orbital Hamilton population (COHP) curves. The influence of reduced VEC for chemical bonding including the formation of interslab Ge2 dimers is also discussed. The magnetic property measurements prove that the non-magnetic Li substitution leads to the ferromagnetic (FM)-like ground state for Ce4LiGe4 and the co-existence of antiferromagntic (AFM) and FM ground states for Sm4LiGe4.

  12. IMPROVED BONDING METHOD

    DOEpatents

    Padgett, E.V. Jr.; Warf, D.H.

    1964-04-28

    An improved process of bonding aluminum to aluminum without fusion by ultrasonic vibrations plus pressure is described. The surfaces to be bonded are coated with an aqueous solution of alkali metal stearate prior to assembling for bonding. (AEC) O H19504 Present information is reviewed on steady state proliferation, differentiation, and maturation of blood cells in mammals. Data are cited from metabolic tracer studies, autoradiographic studies, cytologic studies, studies of hematopoietic response to radiation injuries, and computer analyses of blood cell production. A 3-step model for erythropoiesis and a model for granulocyte kinetics are presented. New approaches to the study of lymphocytopoiesis described include extracorporeal blood irradiation to deplete lymphocytic tissue without direct injury to the formative tissues as a means to study the stressed system, function control, and rates of proliferation. It is pointed out that present knowledge indicates that lymphocytes comprise a mixed family, with diverse life spans, functions, and migration patterns with apparent aimless recycling from modes to lymph to blood to nodes that has not yet been quantitated. Areas of future research are postulated. (70 references.) (C.H.)

  13. Cooperativity in Tetrel Bonds.

    PubMed

    Marín-Luna, Marta; Alkorta, Ibon; Elguero, José

    2016-02-01

    A theoretical study of the cooperativity in linear chains of (H3SiCN)n and (H3SiNC)n complexes connected by tetrel bonds has been carried out by means of MP2 and CCSD(T) computational methods. In all cases, a favorable cooperativity is observed, especially in some of the largest linear chains of (H3SiNC)n, where the effect is so large that the SiH3 group is almost equidistant to the two surrounding CN groups and it becomes planar. In addition, the combination of tetrel bonds with other weak interactions (halogen, chalcogen, pnicogen, triel, beryllium, lithium, and hydrogen bond) has been explored using ternary complexes, (H3SiCN)2:XY and (H3SiNC)2:XY. In all cases, positive cooperativity is obtained, especially in the (H3SiNC)2:ClF and (H3SiNC)2:SHF ternary complexes, where, respectively, halogen and chalcogen shared complexes are formed. PMID:26756083

  14. Communication: Frequency shifts of an intramolecular hydrogen bond as a measure of intermolecular hydrogen bond strengths

    NASA Astrophysics Data System (ADS)

    Gu, Quanli; Trindle, Carl; Knee, J. L.

    2012-09-01

    Infrared-ultraviolet double resonance spectroscopy has been applied to study the infrared spectra of the supersonically cooled gas phase complexes of formic acid, acetic acid, propionic acid, formamide, and water with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. In these complexes each binding partner to 9HFCA can function as both proton donor and acceptor. Relative to its frequency in free 9HFCA, the 9-hydroxy (9OH) stretch is blue shifted in complexes with formic, acetic, and propionic acids, but is red shifted in the complexes with formamide and water. Density functional calculations on complexes of 9HFCA to a variety of H bonding partners with differing proton donor and acceptor abilities reveal that the quantitative frequency shift of the 9OH can be attributed to the balance struck between two competing intermolecular H bonds. More extensive calculations on complexes of glycolic acid show excellent consistency with the experimental frequency shifts.

  15. Coulombic Models in Chemical Bonding.

    ERIC Educational Resources Information Center

    Sacks, Lawrence J.

    1986-01-01

    Compares the coulumbic point charge model for hydrogen chloride with the valence bond model. It is not possible to assign either a nonpolar or ionic canonical form of the valence bond model, while the covalent-ionic bond distribution does conform to the point charge model. (JM)

  16. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...

  17. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...

  18. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...

  19. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...

  20. 46 CFR Sec. 10 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds. (a... awarded work and the furnishing of the performance and payment bonds required by Article 14 of the NSA... of the NSA-LUMPSUMREP Contract, the standard form of individual performance bond (Standard Form...

  1. Annual Bond Referenda Survey: 1998.

    ERIC Educational Resources Information Center

    New Jersey School Boards Association, Trenton.

    An annual school bond survey for New Jersey reveals that while the state's voters had approved 60 percent of the school bond issues in 1998, the communities clearly could not meet the state's multi- billion dollar construction needs on their own. Further, communities with high property taxes had fewer bond elections and approved less of them than…

  2. Reliable four-point flexion test and model for die-to-wafer direct bonding

    SciTech Connect

    Tabata, T. Sanchez, L.; Fournel, F.; Moriceau, H.

    2015-07-07

    For many years, wafer-to-wafer (W2W) direct bonding has been very developed particularly in terms of bonding energy measurement and bonding mechanism comprehension. Nowadays, die-to-wafer (D2W) direct bonding has gained significant attention, for instance, in photonics and microelectro-mechanics, which supposes controlled and reliable fabrication processes. So, whatever the stuck materials may be, it is not obvious whether bonded D2W structures have the same bonding strength as bonded W2W ones, because of possible edge effects of dies. For that reason, it has been strongly required to develop a bonding energy measurement technique which is suitable for D2W structures. In this paper, both D2W- and W2W-type standard SiO{sub 2}-to-SiO{sub 2} direct bonding samples are fabricated from the same full-wafer bonding. Modifications of the four-point flexion test (4PT) technique and applications for measuring D2W direct bonding energies are reported. Thus, the comparison between the modified 4PT and the double-cantilever beam techniques is drawn, also considering possible impacts of the conditions of measures such as the water stress corrosion at the debonding interface and the friction error at the loading contact points. Finally, reliability of a modified technique and a new model established for measuring D2W direct bonding energies is demonstrated.

  3. Switching Bonds in a DNA Gel: An All-DNA Vitrimer

    NASA Astrophysics Data System (ADS)

    Romano, Flavio; Sciortino, Francesco

    2015-02-01

    We design an all-DNA system that behaves like vitrimers, innovative plastics with self-healing and stress-releasing properties. The DNA sequences are engineered to self-assemble first into tetra- and bifunctional units which, upon further cooling, bind to each other forming a fully bonded network gel. An innovative design of the binding regions of the DNA sequences, exploiting a double toehold-mediated strand displacement, generates a network gel which is able to reshuffle its bonds, retaining at all times full bonding. As in vitrimers, the rate of bond switching can be controlled via a thermally activated catalyst, which in the present design is very short DNA strands.

  4. The radiation response of capacitors fabricated on bonded silicon-on-insulator substrates

    SciTech Connect

    McMarr, P.J.; Mrstik, B.J.; Jernigan, G.G.; Lawrence, R.K.

    1997-12-01

    Silicon-on-insulator substrates were manufactured by bonding a thermal oxide of silicon to a silicon wafer. Metal-oxide-silicon capacitors were fabricated on these substrates. Capacitors were also fabricated on unbonded thermal oxides. Capacitance-voltage measurements were performed on the bonded and unbonded oxides, before and after 10 keV x-ray irradiation. The flatband shift for the irradiated bonded oxide was nearly double that of the irradiated unbonded oxide. The radiation-induced shifts of the capacitance-voltage curves are shown to be related to the density differences between the bonded and unbonded oxides.

  5. Double-Sided Cooling Design for Novel Planar Module

    SciTech Connect

    Ning, Puqi; Liang, Zhenxian; Marlino, Laura D; Wang, Fei

    2013-01-01

    A novel packaging structure for medium power modules featuring power semiconductor switches sandwiched between two symmetric substrates that fulfill electrical conduction and insulation functions is presented. Large bonding areas between dies and substrates allow this packaging technology to offer significant improvements in electrical, thermal performance. Double-sided cooling system was dedicatedly analyzed and designed for different applications.

  6. Doubly ionic hydrogen bond interactions within the choline chloride-urea deep eutectic solvent.

    PubMed

    Ashworth, Claire R; Matthews, Richard P; Welton, Tom; Hunt, Patricia A

    2016-07-21

    Deep eutectic solvents (DESs) are exemplars of systems with the ability to form neutral, ionic and doubly ionic H-bonds. Herein, the pairwise interactions of the constituent components of the choline chloride-urea DES are examined. Evidence is found for a tripodal CHCl doubly ionic H-bond motif. Moreover it is found that the covalency of doubly ionic H-bonds can be greater than, or comparable with, neutral and ionic examples. In contrast to many traditional solvents, an "alphabet soup" of many different types of H-bond (OHO[double bond, length as m-dash]C, NHO[double bond, length as m-dash]C, OHCl, NHCl, OHNH, CHCl, CHO[double bond, length as m-dash]C, NHOH and NHNH) can form. These H-bonds exhibit substantial flexibility in terms of number and strength. It is anticipated that H-bonding will have a significant impact on the entropy of the system and thus could play an important role in the formation of the eutectic. The 2 : 1 urea : choline-chloride eutectic point of this DES is often associated with the formation of a [Cl(urea)2](-) complexed anion. However, urea is found to form a H-bonded urea[choline](+) complexed cation that is energetically competitive with [Cl(urea)2](-). The negative charge on [Cl(urea)2](-) is found to remain localised on the chloride, moreover, the urea[choline](+) complexed cation forms the strongest H-bond studied here. Thus, there is potential to consider a urea[choline](+)·urea[Cl](-) interaction. PMID:27328990

  7. Disulfide bond structure of glycoprotein D of herpes simplex virus types 1 and 2.

    PubMed Central

    Long, D; Wilcox, W C; Abrams, W R; Cohen, G H; Eisenberg, R J

    1992-01-01

    Glycoprotein D (gD) is a structural component of the herpes simplex virus envelope which is essential for virus penetration. The function of this protein is highly dependent on its structure, and its structure is dependent on maintenance of three intact disulfide bonds. gD contains six cysteines in its ectodomain whose spacing is conserved among all its homologs in other alphaherpesviruses as well as Marek's disease virus. For other proteins, conservation of cysteine spacing correlates with conservation of disulfide bond structure. We have now solved the disulfide bond structure of gD-1 and gD-2 of herpes simplex virus types 1 and 2, respectively. Two approaches were used. First, we constructed 15 double-Cys mutants of gD-1, representing all possible disulfide pairs. In each case, codons for cysteines were changed to serine. We reasoned that if two cysteines normally form a disulfide bond, double mutations which eliminate one proper bond should be less harmful to gD structure than double mutations which eliminate two disulfide bonds. The mutated genes were cloned into a eucaryotic expression vector, and the proteins were expressed in transiently transfected cells. Three double mutations, Cys-1,5, Cys-2,6, and Cys-3,4 permitted gD-1 folding, processing, transport to the cell surface, and function in virus infection, whereas 12 other double mutations each produced a malfolded and nonfunctional protein. Thus, the three functional double-Cys mutants may represent the actual partners in disulfide bond linkages. The second approach was to define the actual disulfide bond structure of gD by biochemical means. Purified native gD-2 was cleaved by CNBr and proteases, and the peptides were separated by high-performance liquid chromatography. Disulfide-linked peptides were subjected to N-terminal amino acid sequencing. The results show that cysteine 1 (amino acid [aa] 66) is bonded to cysteine 5 (aa 189), cysteine 2 (aa 106) is bonded to cysteine 6 (aa 202), and cysteine 3 (aa

  8. Observing Double Stars

    NASA Astrophysics Data System (ADS)

    Genet, Russell M.; Fulton, B. J.; Bianco, Federica B.; Martinez, John; Baxter, John; Brewer, Mark; Carro, Joseph; Collins, Sarah; Estrada, Chris; Johnson, Jolyon; Salam, Akash; Wallen, Vera; Warren, Naomi; Smith, Thomas C.; Armstrong, James D.; McGaughey, Steve; Pye, John; Mohanan, Kakkala; Church, Rebecca

    2012-05-01

    Double stars have been systematically observed since William Herschel initiated his program in 1779. In 1803 he reported that, to his surprise, many of the systems he had been observing for a quarter century were gravitationally bound binary stars. In 1830 the first binary orbital solution was obtained, leading eventually to the determination of stellar masses. Double star observations have been a prolific field, with observations and discoveries - often made by students and amateurs - routinely published in a number of specialized journals such as the Journal of Double Star Observations. All published double star observations from Herschel's to the present have been incorporated in the Washington Double Star Catalog. In addition to reviewing the history of visual double stars, we discuss four observational technologies and illustrate these with our own observational results from both California and Hawaii on telescopes ranging from small SCTs to the 2-meter Faulkes Telescope North on Haleakala. Two of these technologies are visual observations aimed primarily at published "hands-on" student science education, and CCD observations of both bright and very faint doubles. The other two are recent technologies that have launched a double star renaissance. These are lucky imaging and speckle interferometry, both of which can use electron-multiplying CCD cameras to allow short (30 ms or less) exposures that are read out at high speed with very low noise. Analysis of thousands of high speed exposures allows normal seeing limitations to be overcome so very close doubles can be accurately measured.

  9. On homogeneous L-bonds and heterogeneous L-bonds

    NASA Astrophysics Data System (ADS)

    Konecny, Jan; Ojeda-Aciego, Manuel

    2016-02-01

    In this paper, we deal with suitable generalizations of the notion of bond between contexts, as part of the research area of Formal Concept Analysis. We study different generalizations of the notion of bond within the ? -fuzzy setting. Specifically, given a formal context, there are three prototypical pairs of concept-forming operators, and this immediately leads to three possible versions of the notion of bond (so-called homogeneous bond wrt certain pair of concept-forming operators). The first results show a close correspondence between a homogeneous bond between two contexts and certain special types of mappings between the sets of extents (or intents) of the corresponding concept lattices. Later, we introduce the so-called heterogeneous bonds (considering simultaneously two types of concept-forming operators) and generalize the previous relationship to mappings between the sets of extents (or intents) of the corresponding concept lattices.

  10. Silicon carbide wafer bonding by modified surface activated bonding method

    NASA Astrophysics Data System (ADS)

    Suga, Tadatomo; Mu, Fengwen; Fujino, Masahisa; Takahashi, Yoshikazu; Nakazawa, Haruo; Iguchi, Kenichi

    2015-03-01

    4H-SiC wafer bonding has been achieved by the modified surface activated bonding (SAB) method without any chemical-clean treatment and high temperature annealing. Strong bonding between the SiC wafers with tensile strength greater than 32 MPa was demonstrated at room temperature under 5 kN force for 300 s. Almost the entire wafer has been bonded very well except a small peripheral region and few voids. The interface structure was analyzed to verify the bonding mechanism. It was found an amorphous layer existed as an intermediate layer at the interface. After annealing at 1273 K in vacuum for 1 h, the bonding tensile strength was still higher than 32 MPa. The interface changes after annealing were also studied. The results show that the thickness of the amorphous layer was reduced to half after annealing.

  11. NXY halogen bonds. Comparison with NHY H-bonds and CXY halogen bonds.

    PubMed

    Nepal, Binod; Scheiner, Steve

    2016-07-21

    Quantum calculations examine how the NHY H-bond compares to the equivalent NXY halogen bond, as well as to comparable CH/CX donors. Succinimide and saccharin, and their corresponding halogen-substituted derivatives, are chosen as the prototype NH/NX donors, paired with a wide range of electron donor molecules. The NHY H-bond is weakened if the bridging H is replaced by Cl, and strengthened by I; a Br halogen bond is roughly comparable to a H-bond. The lone pairs of the partner molecule are stronger electron donors than are π-systems. Whereas Coulombic forces represent the largest fraction of the attractive force in the H-bonds, induction energy is magnified in the halogen bonds, surpassing electrostatics in several cases. Mutation of NH/NX to CH/CX weakens the binding energy to roughly half its original value, while also lengthening the intermolecular distances by 0.3-0.8 Å. PMID:27327538

  12. Comparison of Bond in Roll-bonded and Adhesively Bonded Aluminums

    NASA Technical Reports Server (NTRS)

    Schwensfeir, R. J., Jr.; Trenkler, G.; Delagi, R. G.; Forster, J. A.

    1985-01-01

    Lap-shear and peel test measurements of bond strength have been carried out as part of an investigation of roll bonding of 2024 and 7075 aluminum alloys. Shear strengths of the bonded material in the F temper are in the range of 14 to 16 ksi. Corresponding peel strengths are 120 to 130 lb/inch. These values, which are three to five times those reported in the literature for adhesively bonded 2024 and 7075, are a result of the true metallurgical bond achieved. The effects of heat-treating the bonded material are described and the improvements in bond strength discussed relative to the shear strength of the parent material. The significance of the findings for aerospace applications is discussed.

  13. Modulating the strength of tetrel bonding through beryllium bonding.

    PubMed

    Liu, Mingxiu; Yang, Li; Li, Qingzhong; Li, Wenzuo; Cheng, Jianbo; Xiao, Bo; Yu, Xuefang

    2016-08-01

    Quantum chemical calculations were performed to investigate the stability of the ternary complexes BeH2···XMH3···NH3 (X = F, Cl, and Br; M = C, Si, and Ge) and the corresponding binary complexes at the atomic level. Our results reveal that the stability of the XMH3···BeH2 complexes is mainly due to both a strong beryllium bond and a weak tetrel-hydride interaction, while the XMH3···NH3 complexes are stabilized by a tetrel bond. The beryllium bond with a halogen atom as the electron donor has many features in common with a beryllium bond with an O or N atom as the electron donor, although they do exhibit some different characteristics. The stability of the XMH3···NH3 complex is dominated by the electrostatic interaction, while the orbital interaction also makes an important contribution. Interestingly, as the identities of the X and M atoms are varied, the strength of the tetrel bond fluctuates in an irregular manner, which can explained by changes in electrostatic potentials and orbital interactions. In the ternary systems, both the beryllium bond and the tetrel bond are enhanced, which is mainly ascribed to increased electrostatic potentials on the corresponding atoms and charge transfer. In particular, when compared to the strengths of the tetrel and beryllium bonds in the binary systems, in the ternary systems the tetrel bond is enhanced to a greater degree than the beryllium bond. Graphical Abstract A tetrel bond can be strengthened greatly by a beryllium bond. PMID:27464738

  14. Solder extrusion pressure bonding process and bonded products produced thereby

    DOEpatents

    Beavis, L.C.; Karnowsky, M.M.; Yost, F.G.

    1992-06-16

    Disclosed is a process for production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about [minus]40 C and 110 C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

  15. Solder extrusion pressure bonding process and bonded products produced thereby

    SciTech Connect

    Beavis, L.C.; Karnowsky, M.M.; Yost, F.G.

    1990-12-31

    Production of soldiered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about {minus}40{degrees}C and 110{degrees}C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

  16. Solder extrusion pressure bonding process and bonded products produced thereby

    DOEpatents

    Beavis, Leonard C.; Karnowsky, Maurice M.; Yost, Frederick G.

    1992-01-01

    Production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about -40.degree. C. and 110.degree. C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

  17. 19 CFR 113.12 - Bond application.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond application. In order to insure that the revenue is adequately protected the port director may require...

  18. 19 CFR 113.12 - Bond application.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond application. In order to insure that the revenue is adequately protected the port director may require...

  19. 19 CFR 113.12 - Bond application.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond application. In order to insure that the revenue is adequately protected the port director may require...

  20. 19 CFR 113.12 - Bond application.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond application. In order to insure that the revenue is adequately protected the port director may require...

  1. 19 CFR 113.12 - Bond application.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Bond application. 113.12 Section 113.12 Customs... CUSTOMS BONDS Bond Application and Approval of Bond § 113.12 Bond application. (a) Single entry bond application. In order to insure that the revenue is adequately protected the port director may require...

  2. Combined effect of chemical pressure and valence electron concentration through the electron-deficient Li substitution on the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system

    SciTech Connect

    Nam, Gnu; Jeon, Jieun; Kim, Youngjo; Kwon Kang, Sung; Ahn, Kyunghan; You, Tae-Soo

    2013-09-15

    Four members of the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system have been prepared by high-temperature reaction method and characterized by X-ray diffractions. All compounds crystallize in the orthorhombic Gd{sub 5}Si{sub 4}-type structure (space group Pnma, Pearson code oP16) with bonding interactions for interslab Ge{sub 2} dimers. The Li substitution for rare-earth elements in the RE{sub 4}LiGe{sub 4} system leads to a combined effect of the increased chemical pressure and the decreased valance electron concentration (VEC), which eventually results in the structure transformation from the Sm{sub 5}Ge{sub 4}-type with all broken interslab Ge–Ge bond for the parental RE{sub 5}Ge{sub 4} to the Gd{sub 5}Si{sub 4}-type structure for the ternary RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. Site-preference between rare-earth metals and Li is proven to generate energetically the most favorable atomic arrangements according to coloring-problem, and the rationale is provided using both the size-factor and the electronic-factor related, respectively, to site-volume and electronegativity as well as QVAL values. Tight-binding, linear-muffin-tin-orbital (TB-LMTO) calculations are performed to investigate electronic densities of states (DOS) and crystal orbital Hamilton population (COHP) curves. The influence of reduced VEC for chemical bonding including the formation of interslab Ge{sub 2} dimers is also discussed. The magnetic property measurements prove that the non-magnetic Li substitution leads to the ferromagnetic (FM)-like ground state for Ce{sub 4}LiGe{sub 4} and the co-existence of antiferromagntic (AFM) and FM ground states for Sm{sub 4}LiGe{sub 4}. - Graphical abstract: Reported is a combined effect of the chemical pressure and the reduced VEC caused by the smaller monovalent non-magnetic Li substitution for the larger trivalent magnetic rare-earth metals in the RE{sub 4}LiGe{sub 4} (RE=La, Ce, Pr, and Sm) system. This results in the structure

  3. Better Bonded Ethernet Load Balancing

    SciTech Connect

    Gabler, Jason

    2006-09-29

    When a High Performance Storage System's mover shuttles large amounts of data to storage over a single Ethernet device that single channel can rapidly become saturated. Using Linux Ethernet channel bonding to address this and similar situations was not, until now, a viable solution. The various modes in which channel bonding could be configured always offered some benefit but only under strict conditions or at a system resource cost that was greater than the benefit gained by using channel bonding. Newer bonding modes designed by various networking hardware companies, helpful in such networking scenarios, were already present in their own switches. However, Linux-based systems were unable to take advantage of those new modes as they had not yet been implemented in the Linux kernel bonding driver. So, except for basic fault tolerance, Linux channel bonding could not positively combine separate Ethernet devices to provide the necessary bandwidth.

  4. Bond Sensitivity to Silicone Contamination

    NASA Technical Reports Server (NTRS)

    Caldwell, G. A.; Hudson, W. D.; Hudson, W. D.; Cash, Stephen F. (Technical Monitor)

    2003-01-01

    Currently during fabrication of the Space Shuttle booster rocket motors, the use of silicone and silicone-containing products is prohibited in most applications. Many shop aids and other materials containing silicone have the potential, if they make contact with a bond surface, to transfer some of the silicone to the substrates being bonded. Such transfer could result in a reduction of the bond strength or even failure of the subsequent bonds. This concern is driving the need to understand the effect of silicones and the concentration needed to affect a given bond-line strength. Additionally, as silicone detection methods used for materials acceptance improve what may have gone unnoticed earlier is now being detected. Thus, realistic silicone limits for process materials (below which bond performance is satisfactory) are needed rather than having an absolute no silicone permitted policy.

  5. Fatigue life prediction of bonded primary joints

    NASA Technical Reports Server (NTRS)

    Knauss, J. F.

    1979-01-01

    The validation of a proposed fatigue life prediction methodology was sought through the use of aluminum butt and scarf joint and graphite/epoxy butt joint specimens in a constant amplitude fatigue environment. The structural properties of the HYSOL 9313 adhesive system were obtained by mechanical test of molded heat adhesive specimens. Aluminum contoured double cantilever beam specimens were used to generate crack velocity versus stress intensity factor data. The specific objectives were: (1) to ascertain the feasibility of predicting fatigue failure of an adhesive in a primary bonded composite structure by incorporating linear elastic crack growth behavior; and (2) to ascertain if acoustic emission and/or compliance measurement techniques can be used to detect flaws.

  6. Wafer bonded epitaxial templates for silicon heterostructures

    NASA Technical Reports Server (NTRS)

    Atwater, Harry A., Jr. (Inventor); Zahler, James M. (Inventor); Morral, Anna Fontcubera I (Inventor)

    2008-01-01

    A heterostructure device layer is epitaxially grown on a virtual substrate, such as an InP/InGaAs/InP double heterostructure. A device substrate and a handle substrate form the virtual substrate. The device substrate is bonded to the handle substrate and is composed of a material suitable for fabrication of optoelectronic devices. The handle substrate is composed of a material suitable for providing mechanical support. The mechanical strength of the device and handle substrates is improved and the device substrate is thinned to leave a single-crystal film on the virtual substrate such as by exfoliation of a device film from the device substrate. An upper portion of the device film exfoliated from the device substrate is removed to provide a smoother and less defect prone surface for an optoelectronic device. A heterostructure is epitaxially grown on the smoothed surface in which an optoelectronic device may be fabricated.

  7. Interlayer bonding in IIb chlorite

    SciTech Connect

    Bish, D.L.; Giese, R.F. Jr.

    1981-01-01

    The interlayer bond energy of a IIb-4 chlorite has been calculated as a function of layer charge, the site of the charge and the selective replacement of hydroxyl groups by fluoride ions. Long hydrogen bonds between the hydroxide sheet and the adjacent oxygens are strong and by themselves sufficient to create a stable structure. Coupled substitutions giving the 2:1 layer a negative charge and the hydroxide sheet a positive charge increase substantially the interlayer bond energy. 3 figures.

  8. Photoinduced hydrogen-bonding dynamics.

    PubMed

    Chu, Tian-Shu; Xu, Jinmei

    2016-09-01

    Hydrogen bonding dynamics has received extensive research attention in recent years due to the significant advances in femtolaser spectroscopy experiments and quantum chemistry calculations. Usually, photoexcitation would cause changes in the hydrogen bonding formed through the interaction between hydrogen donor and acceptor molecules on their ground electronic states, and such transient strengthening or weakening of hydrogen bonding could be crucial for the photophysical transformations and the subsequent photochemical reactions that occurred on a time scale from tens of femtosecond to a few nanoseconds. In this article, we review the combined experimental and theoretical studies focusing on the ultrafast electronic and vibrational hydrogen bonding dynamics. Through these studies, new mechanisms and proposals and common rules have been put forward to advance our understanding of the hydrogen bondings dynamics in a variety of important photoinduced phenomena like photosynthesis, dual fluorescence emission, rotational reorientation, excited-state proton transfer and charge transfer processes, chemosensor fluorescence sensing, rearrangements of the hydrogen-bond network including forming and breaking hydrogen bond in water. Graphical Abstract We review the recent advances on exploring the photoinduced hydrogen bonding dynamics in solutions through a joint approach of laser spectroscopy and theoretical calculation. The reviewed studies have put forward a new mechanism, new proposal, and new rule for a variety of photoinduced phenomena such as photosynthesis, dual fluorescence emission, rotational reorientation, excited-state proton transfer and charge transfer, chemosensor fluorescence sensing, and rearrangements of the hydrogen-bond network in water. PMID:27491849

  9. 30 CFR 281.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF MINERALS OTHER THAN OIL, GAS, AND SULPHUR IN THE OUTER CONTINENTAL SHELF Financial Considerations §...

  10. 29 CFR 2580.412-19 - Term of the bond, discovery period, other bond clauses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Term of the bond, discovery period, other bond clauses... SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580.412-19 Term of the bond, discovery... new bond must be obtained each year. There is nothing in the Act that prohibits a bond for a...

  11. σ-Hole Bond vs π-Hole Bond: A Comparison Based on Halogen Bond.

    PubMed

    Wang, Hui; Wang, Weizhou; Jin, Wei Jun

    2016-05-11

    The σ-hole and π-hole are the regions with positive surface electrostatic potential on the molecule entity; the former specifically refers to the positive region of a molecular entity along extension of the Y-Ge/P/Se/X covalent σ-bond (Y = electron-rich group; Ge/P/Se/X = Groups IV-VII), while the latter refers to the positive region in the direction perpendicular to the σ-framework of the molecular entity. The directional noncovalent interactions between the σ-hole or π-hole and the negative or electron-rich sites are named σ-hole bond or π-hole bond, respectively. The contributions from electrostatic, charge transfer, and other terms or Coulombic interaction to the σ-hole bond and π-hole bond were reviewed first followed by a brief discussion on the interplay between the σ-hole bond and the π-hole bond as well as application of the two types of noncovalent interactions in the field of anion recognition. It is expected that this review could stimulate further development of the σ-hole bond and π-hole bond in theoretical exploration and practical application in the future. PMID:26886515

  12. Topological Quantum Double

    NASA Astrophysics Data System (ADS)

    Bonneau, Philippe

    Following a preceding paper showing how the introduction of a t.v.s. topology on quantum groups led to a remarkable unification and rigidification of the different definitions, we adapt here, in the same way, the definition of quantum double. This topological double is dualizable and reflexive (even for infinite dimensional algebras). In a simple case we show, considering the double as the "zero class" of an extension theory, the uniqueness of the double structure as a quasi-Hopf algebra. A la suite d'un précédent article montrant comment l'introduction d'une topologie d'e.v.t. sur les groupes quantiques permet une unification et une rigidification remarquables des différentes définitions, on adapte ici de la même manière la définition du double quantique. Ce double topologique est alors dualisable et reflexif (même pour des algèbres de dimension infinie). Dans un cas simple on montre, en considérant le double comme la "classe zéro" d'une théorie d'extensions, l'unicité de cette structure comme algèbre quasi-Hopf.

  13. Emerging double helical nanostructures

    NASA Astrophysics Data System (ADS)

    Zhao, Meng-Qiang; Zhang, Qiang; Tian, Gui-Li; Wei, Fei

    2014-07-01

    As one of the most important and land-mark structures found in nature, a double helix consists of two congruent single helices with the same axis or a translation along the axis. This double helical structure renders the deoxyribonucleic acid (DNA) the crucial biomolecule in evolution and metabolism. DNA-like double helical nanostructures are probably the most fantastic yet ubiquitous geometry at the nanoscale level, which are expected to exhibit exceptional and even rather different properties due to the unique organization of the two single helices and their synergistic effect. The organization of nanomaterials into double helical structures is an emerging hot topic for nanomaterials science due to their promising exceptional unique properties and applications. This review focuses on the state-of-the-art research progress for the fabrication of double-helical nanostructures based on `bottom-up' and `top-down' strategies. The relevant nanoscale, mesoscale, and macroscopic scale fabrication methods, as well as the properties of the double helical nanostructures are included. Critical perspectives are devoted to the synthesis principles and potential applications in this emerging research area. A multidisciplinary approach from the scope of nanoscience, physics, chemistry, materials, engineering, and other application areas is still required to the well-controlled and large-scale synthesis, mechanism, property, and application exploration of double helical nanostructures.

  14. Pauling bond strength, bond length and electron density distribution

    SciTech Connect

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.; Iversen, Bo B.; Spackman, M. A.

    2014-01-18

    A power law regression equation, = 1.46(<ρ(rc)>/r)-0.19, connecting the average experimental bond lengths, , with the average accumulation of the electron density at the bond critical point, <ρ(rc)>, between bonded metal M and oxygen atoms, determined at ambient conditions for oxide crystals, where r is the row number of the M atom, is similar to the regression equation R(M-O) = 1.39(ρ(rc)/r)-0.21 determined for three perovskite crystals for pressures as high as 80 GPa. The two equations are also comparable with those, = 1.43(/r)-0.21, determined for a large number of oxide crystals at ambient conditions and = 1.39(/r)-0.22, determined for geometry optimized hydroxyacid molecules, that connect the bond lengths to the average Pauling electrostatic bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the two sets of equations connecting ρ(rc) and the Pauling bond strength s with bond length, it appears that Pauling’s simple definition of bond strength closely mimics the accumulation of the electron density between bonded pairs of atoms. The similarity of the expressions for the crystals and molecules is compelling evidence that the M-O bonded interactions for the crystals and molecules 2 containing the same bonded interactions are comparable. Similar expressions, connecting bond lengths and bond strength, have also been found to hold for fluoride, nitride and sulfide molecules and crystals. The Brown-Shannon bond valence, σ, power law expression σ = [R1/(R(M-O)]N that has found wide use in crystal chemistry, is shown to be connected to a more universal expression determined for oxides and the perovskites, <ρ(rc)> = r[(1.41)/]4.76, demonstrating that the bond valence for a bonded interaction is likewise closely connected to the accumulation of the electron density between the bonded atoms. Unlike the Brown-Shannon expression, it is universal in that it holds for the M

  15. Bond strength of pressure sensitive adhesives for CFRP aluminium-alloy hybrid beams under impact loading

    NASA Astrophysics Data System (ADS)

    Sato, C.

    2003-09-01

    This paper discusses the impact absorbing capabilities of CFRP aluminium-alloy hybrid beams bonded with double-coated pressure sensitive adhesive tapes. Two sorts of double-coated adhesive tapes (VHB and SBT, 3M) were used in experiments. The strength and absorbed energy of the beams under impact loading were measured using an instrumented Charpy tester. Using the beams having the different adhesive tapes and the CFRP of different length, the variations of the strength and the absorbed energy were investigated. The beams bonded with VHB showed sufficient strength and absorbed energy. SBT showed also great capability of absorbing impact energy.

  16. Ultrasonic Bonding to Metalized Plastic

    NASA Technical Reports Server (NTRS)

    Conroy, B. L.; Cruzan, C. T.

    1986-01-01

    New technique makes it possible to bond wires ultrasonically to conductor patterns on such soft substrates as plain or ceramic-filled polytetrafluoroethylene. With ultrasonic bonding, unpackaged chips attached to soft circuit boards. Preferred because chips require substrate area and better matched electrically to circuit board at high frequencies.

  17. Microwave bonding of MEMS component

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Mai, John D. (Inventor); Jackson, Henry W. (Inventor); Budraa, Nasser K. (Inventor); Pike, William T. (Inventor)

    2005-01-01

    Bonding of MEMs materials is carried out using microwave. High microwave absorbing films are placed within a microwave cavity, and excited to cause selective heating in the skin of the material. This causes heating in one place more than another. Thereby minimizing the effects of the bonding microwave energy.

  18. Weld-bonded titanium structures

    NASA Technical Reports Server (NTRS)

    Vaughan, R. W.; Creedon, J. F. (Inventor)

    1976-01-01

    Structurally stronger titanium articles are produced by a weld-bonding technique comprising fastening at least two plates of titanium together using spotwelding and curing an adhesive interspersed between the spot-weld nuggets. This weld-bonding may be employed to form lap joints or to stiffen titanium metal plates.

  19. Computational Chemistry of Adhesive Bonds

    NASA Technical Reports Server (NTRS)

    Phillips, Donald H.

    1999-01-01

    This investigation is intended to determine the electrical mechanical, and chemical properties of adhesive bonds at the molecular level. The initial determinations will be followed by investigations of the effects of environmental effects on the chemistry and properties of the bond layer.

  20. Coulombic Models in Chemical Bonding.

    ERIC Educational Resources Information Center

    Sacks, Lawrence J.

    1986-01-01

    Describes a bonding theory which provides a framework for the description of a wide range of substances and provides quantitative information of remarkable accuracy with far less computational effort than that required of other approaches. Includes applications, such as calculation of bond energies of two binary hydrides (methane and diborane).…

  1. Social bonding: regulation by neuropeptides

    PubMed Central

    Lieberwirth, Claudia; Wang, Zuoxin

    2014-01-01

    Affiliative social relationships (e.g., among spouses, family members, and friends) play an essential role in human society. These relationships affect psychological, physiological, and behavioral functions. As positive and enduring bonds are critical for the overall well-being of humans, it is not surprising that considerable effort has been made to study the neurobiological mechanisms that underlie social bonding behaviors. The present review details the involvement of the nonapeptides, oxytocin (OT), and arginine vasopressin (AVP), in the regulation of social bonding in mammals including humans. In particular, we will discuss the role of OT and AVP in the formation of social bonds between partners of a mating pair as well as between parents and their offspring. Furthermore, the role of OT and AVP in the formation of interpersonal bonding involving trust is also discussed. PMID:25009457

  2. Quantum finance Hamiltonian for coupon bond European and barrier options

    NASA Astrophysics Data System (ADS)

    Baaquie, Belal E.

    2008-03-01

    Coupon bond European and barrier options are financial derivatives that can be analyzed in the Hamiltonian formulation of quantum finance. Forward interest rates are modeled as a two-dimensional quantum field theory and its Hamiltonian and state space is defined. European and barrier options are realized as transition amplitudes of the time integrated Hamiltonian operator. The double barrier option for a financial instrument is “knocked out” (terminated with zero value) if the price of the underlying instrument exceeds or falls below preset limits; the barrier option is realized by imposing boundary conditions on the eigenfunctions of the forward interest rates’ Hamiltonian. The price of the European coupon bond option and the zero coupon bond barrier option are calculated. It is shown that, is general, the constraint function for a coupon bond barrier option can—to a good approximation—be linearized. A calculation using an overcomplete set of eigenfunctions yields an approximate price for the coupon bond barrier option, which is given in the form of an integral of a factor that results from the barrier condition times another factor that arises from the payoff function.

  3. Double Degenerate Binary Systems

    SciTech Connect

    Yakut, K.

    2011-09-21

    In this study, angular momentum loss via gravitational radiation in double degenerate binary (DDB)systems (NS + NS, NS + WD, WD + WD, and AM CVn) is studied. Energy loss by gravitational waves has been estimated for each type of systems.

  4. Double aortic arch

    MedlinePlus

    ... double aortic arch may press on the windpipe (trachea) and esophagus, leading to trouble breathing and swallowing. ... to relieve pressure on the esophagus and windpipe (trachea). The surgeon ties off the smaller branch and ...

  5. 27 CFR 24.153 - Strengthening bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Strengthening bonds. In any instance where the penal sum of the bond on file becomes insufficient, the principal shall either give a strengthening bond with the same surety to attain a sufficient penal sum or give a new bond covering the entire liability. Strengthening bonds will not be approved where any notation...

  6. 8 CFR 103.6 - Surety bonds.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... a public charge. A bond may also be cancelled in order to allow substitution of another bond. A... surety bonds posted in immigration cases shall be executed on Form I-352, Immigration Bond, a copy of... to approve a bond, a formal agreement to extension of liability of surety, a request for delivery...

  7. 48 CFR 252.217-7008 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... corporate surety bond. (d) If any surety upon any bond furnished in connection with a job order under this...) If the solicitation requires an offeror to submit a bid bond, the Offeror may furnish, instead, an annual bid bond (or evidence thereof) or an annual performance and payment bond (or evidence thereof)....

  8. 48 CFR 252.217-7008 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... corporate surety bond. (d) If any surety upon any bond furnished in connection with a job order under this...) If the solicitation requires an offeror to submit a bid bond, the Offeror may furnish, instead, an annual bid bond (or evidence thereof) or an annual performance and payment bond (or evidence thereof)....

  9. 8 CFR 103.6 - Surety bonds.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... a public charge. A bond may also be cancelled in order to allow substitution of another bond. A... surety bonds posted in immigration cases shall be executed on Form I-352, Immigration Bond, a copy of... to approve a bond, a formal agreement to extension of liability of surety, a request for delivery...

  10. 48 CFR 252.217-7008 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... corporate surety bond. (d) If any surety upon any bond furnished in connection with a job order under this...) If the solicitation requires an offeror to submit a bid bond, the Offeror may furnish, instead, an annual bid bond (or evidence thereof) or an annual performance and payment bond (or evidence thereof)....

  11. 8 CFR 103.6 - Surety bonds.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... a public charge. A bond may also be cancelled in order to allow substitution of another bond. A... surety bonds posted in immigration cases shall be executed on Form I-352, Immigration Bond, a copy of... to approve a bond, a formal agreement to extension of liability of surety, a request for delivery...

  12. Microleakage of bonded amalgam restorations: effect of thermal cycling.

    PubMed

    Helvatjoglou-Antoniades, M; Theodoridou-Pahini, S; Papadogiannis, Y; Karezis, A

    2000-01-01

    This study examined the effect of thermal cycling on the microleakage of bonded amalgam restorations. Three dental amalgam alloys and a gallium alloy were tested with two adhesive resin systems and copal varnish as a control. Class V cavity preparations were prepared on 168 freshly extracted premolars or molars. The preparations were placed parallel to and 1.0 mm occlusal to the cementoenamel junction (CEJ). Four groups of 42 teeth each were treated with one of the following adhesive dentin systems: Bond-It, All-Bond 2/Resinomer or a copal varnish (Copalite). The four groups of 42 teeth each were then restored with one of three dental amalgams: Orosphere Plus, Indiloy, Oralloy or a Gallium alloy (Galloy), resulting in 12 test groups of 14 teeth each. The specimens were stored in double distilled water at 37 degrees C for 24 hours. Final contouring and polishing of the restorations were performed under water spray. Half of the restorations in each group were thermocycled for 3000 cycles (5 degrees C-37 degrees C-55 degrees C-37 degrees C) with a dwell time of 15 sec at each temperature. The other half were stored in double distilled water at 37 degrees C for 24 hours. Then all 168 restorations were stained with dye, sectioned and scored for microleakage. Results showed that the adhesive dentin systems reduced microleakage in amalgam restorations compared to copal varnish only in non-thermocycled specimens. Statistical analysis of the results showed that there was an extremely significant difference (p < 0.001) in microleakage between the non-thermocycled and the thermocycled specimens in all test groups, whereas, there was no significant difference (p > 0.05) among thermocycled specimens. The reduction of microleakage was not significantly different between Bond-It and All-Bond 2/Resinomer in non-thermocycled specimens. Oralloy showed the most microleakage in the non-thermocycled groups when compared to the other alloys using the same adhesive liner. PMID:11203837

  13. Improved Method for the Diimide Reduction of Multiple Bonds on Solid-Supported Substrates

    PubMed Central

    Buszek, Keith R.; Brown, Neil

    2009-01-01

    A mild and improved method for reducing multiple bonds on various resins with diimide is described. The simple procedure readily generates diimide from 2-nitrobenzenesulfonohydrazide and triethylamine at room temperature. A number of representative multiple bonds in various steric and electronic environments were examined, including polar double bonds such as carbonyl and azo, for ease and selectivity of reduction. A general trend of reactivity was identified which revealed, inter alia, that terminal olefins, 1,2-disubstituted olefins, electron-poor olefins, and terminal alkynes were the most easily reduced. PMID:17367188

  14. Smart interfacial bonding alloys

    SciTech Connect

    R. Q. Hwang; J. C. Hamilton; J. E. Houston

    1999-04-01

    The goal of this LDRD was to explore the use of the newly discovered strain-stabilized 2-D interfacial alloys as smart interface bonding alloys (SIBA). These materials will be used as templates for the heteroepitaxial growth of metallic thin films. SIBA are formed by two metallic components which mix at an interface to relieve strain and prevent dislocations from forming in subsequent thin film growth. The composition of the SIBA is determined locally by the amount of strain, and therefore can react smartly to areas of the highest strain to relieve dislocations. In this way, SIBA can be used to tailor the dislocation structure of thin films. This project included growth, characterization and modeling of films grown using SIBA templates. Characterization will include atomic imaging of the dislocations structure, measurement of the mechanical properties of the film using interface force microscopy (IFM) and the nanoindenter, and measurement of the electronic structure of the SIBA with synchrotron photoemission. Resistance of films to sulfidation and oxidation will also be examined. The Paragon parallel processing computer will be used to calculate the structure of the SIBA and thin films in order to develop ability to predict and tailor SIBA and thin film behavior. This work will lead to the possible development of a new class of thin film materials with properties tailored by varying the composition of the SIBA, serving as a buffer layer to relieve the strain between the substrate and the thin film. Such films will have improved mechanical and corrosion resistance allowing application as protective barriers for weapons applications. They will also exhibit enhanced electrical conductivity and reduced electromigration making them particularly suitable for application as interconnects and other electronic needs.

  15. Tensile Bond Strength of Latex-Modified Bonded Concrete Overlays

    NASA Astrophysics Data System (ADS)

    Dubois, Cameron; Ramseyer, Chris

    2010-10-01

    The tensile bond strength of bonded concrete overlays was tested using the in-situ pull-off method described in ASTM C 1583 with the goal of determining whether adding latex to the mix design increases bond strength. One slab of ductile concrete (f'c > 12,000 psi) was cast with one half tined, i.e. roughened, and one half steel-troweled, i.e. smooth. The slab surface was sectioned off and overlay mixtures containing different latex contents cast in each section. Partial cores were drilled perpendicular to the surface through the overlay into the substrate. A tensile loading device applied a direct tensile load to each specimen and the load was increased until failure occurred. The tensile bond strength was then calculated for comparison between the specimens.

  16. Ultrasonic Imaging Of Bond Layers Through Bond Layers

    NASA Technical Reports Server (NTRS)

    Chern, E. James

    1992-01-01

    Combination of hardware and software helps ultrasonic C-scan inspection system create images of bond layer in laminated composite material, even when obscured by another bond layer. Produces image of both layers in single scan. Includes ultrasonic transducer, pulser/receiver, mechanical scanner, personal computer as controller, and electronic circuitry that gates first and second peak signals, detects peaks, and feeds resulting amplitude data to computer.

  17. Fusion bonding and alignment fixture

    DOEpatents

    Ackler, Harold D.; Swierkowski, Stefan P.; Tarte, Lisa A.; Hicks, Randall K.

    2000-01-01

    An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all the components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

  18. Method for vacuum fusion bonding

    DOEpatents

    Ackler, Harold D.; Swierkowski, Stefan P.; Tarte, Lisa A.; Hicks, Randall K.

    2001-01-01

    An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

  19. Fast and accurate predictions of covalent bonds in chemical space.

    PubMed

    Chang, K Y Samuel; Fias, Stijn; Ramakrishnan, Raghunathan; von Lilienfeld, O Anatole

    2016-05-01

    We assess the predictive accuracy of perturbation theory based estimates of changes in covalent bonding due to linear alchemical interpolations among molecules. We have investigated σ bonding to hydrogen, as well as σ and π bonding between main-group elements, occurring in small sets of iso-valence-electronic molecules with elements drawn from second to fourth rows in the p-block of the periodic table. Numerical evidence suggests that first order Taylor expansions of covalent bonding potentials can achieve high accuracy if (i) the alchemical interpolation is vertical (fixed geometry), (ii) it involves elements from the third and fourth rows of the periodic table, and (iii) an optimal reference geometry is used. This leads to near linear changes in the bonding potential, resulting in analytical predictions with chemical accuracy (∼1 kcal/mol). Second order estimates deteriorate the prediction. If initial and final molecules differ not only in composition but also in geometry, all estimates become substantially worse, with second order being slightly more accurate than first order. The independent particle approximation based second order perturbation theory performs poorly when compared to the coupled perturbed or finite difference approach. Taylor series expansions up to fourth order of the potential energy curve of highly symmetric systems indicate a finite radius of convergence, as illustrated for the alchemical stretching of H2 (+). Results are presented for (i) covalent bonds to hydrogen in 12 molecules with 8 valence electrons (CH4, NH3, H2O, HF, SiH4, PH3, H2S, HCl, GeH4, AsH3, H2Se, HBr); (ii) main-group single bonds in 9 molecules with 14 valence electrons (CH3F, CH3Cl, CH3Br, SiH3F, SiH3Cl, SiH3Br, GeH3F, GeH3Cl, GeH3Br); (iii) main-group double bonds in 9 molecules with 12 valence electrons (CH2O, CH2S, CH2Se, SiH2O, SiH2S, SiH2Se, GeH2O, GeH2S, GeH2Se); (iv) main-group triple bonds in 9 molecules with 10 valence electrons (HCN, HCP, HCAs, HSiN, HSi

  20. Fast and accurate predictions of covalent bonds in chemical space

    NASA Astrophysics Data System (ADS)

    Chang, K. Y. Samuel; Fias, Stijn; Ramakrishnan, Raghunathan; von Lilienfeld, O. Anatole

    2016-05-01

    We assess the predictive accuracy of perturbation theory based estimates of changes in covalent bonding due to linear alchemical interpolations among molecules. We have investigated σ bonding to hydrogen, as well as σ and π bonding between main-group elements, occurring in small sets of iso-valence-electronic molecules with elements drawn from second to fourth rows in the p-block of the periodic table. Numerical evidence suggests that first order Taylor expansions of covalent bonding potentials can achieve high accuracy if (i) the alchemical interpolation is vertical (fixed geometry), (ii) it involves elements from the third and fourth rows of the periodic table, and (iii) an optimal reference geometry is used. This leads to near linear changes in the bonding potential, resulting in analytical predictions with chemical accuracy (˜1 kcal/mol). Second order estimates deteriorate the prediction. If initial and final molecules differ not only in composition but also in geometry, all estimates become substantially worse, with second order being slightly more accurate than first order. The independent particle approximation based second order perturbation theory performs poorly when compared to the coupled perturbed or finite difference approach. Taylor series expansions up to fourth order of the potential energy curve of highly symmetric systems indicate a finite radius of convergence, as illustrated for the alchemical stretching of H 2+ . Results are presented for (i) covalent bonds to hydrogen in 12 molecules with 8 valence electrons (CH4, NH3, H2O, HF, SiH4, PH3, H2S, HCl, GeH4, AsH3, H2Se, HBr); (ii) main-group single bonds in 9 molecules with 14 valence electrons (CH3F, CH3Cl, CH3Br, SiH3F, SiH3Cl, SiH3Br, GeH3F, GeH3Cl, GeH3Br); (iii) main-group double bonds in 9 molecules with 12 valence electrons (CH2O, CH2S, CH2Se, SiH2O, SiH2S, SiH2Se, GeH2O, GeH2S, GeH2Se); (iv) main-group triple bonds in 9 molecules with 10 valence electrons (HCN, HCP, HCAs, HSiN, HSi

  1. Locally measuring the adhesion of InP directly bonded on sub-100 nm patterned Si

    NASA Astrophysics Data System (ADS)

    Pantzas, K.; Le Bourhis, E.; Patriarche, G.; Troadec, D.; Beaudoin, G.; Itawi, A.; Sagnes, I.; Talneau, A.

    2016-03-01

    A nano-scale analogue to the double cantilever experiment that combines instrumented nano-indentation and atomic force microscopy is used to precisely and locally measure the adhesion of InP bonded on sub-100 nm patterned Si using oxide-free or oxide-mediated bonding. Surface-bonding energies of 0.548 and 0.628 J m-2, respectively, are reported. These energies correspond in turn to 51% and 57% of the surface bonding energy measured in unpatterned regions on the same samples, i.e. the proportion of unetched Si surface in the patterned areas. The results show that bonding on patterned surfaces can be as robust as on unpatterned surfaces, provided care is taken with the post-patterning surface preparation process and, therefore, open the path towards innovative designs that include patterns embedded in the Si guiding layer of hybrid III-V/Si photonic integrated circuits.

  2. Locally measuring the adhesion of InP directly bonded on sub-100 nm patterned Si.

    PubMed

    Pantzas, K; Bourhis, E Le; Patriarche, G; Troadec, D; Beaudoin, G; Itawi, A; Sagnes, I; Talneau, A

    2016-03-18

    A nano-scale analogue to the double cantilever experiment that combines instrumented nano-indentation and atomic force microscopy is used to precisely and locally measure the adhesion of InP bonded on sub-100 nm patterned Si using oxide-free or oxide-mediated bonding. Surface-bonding energies of 0.548 and 0.628 J m(-2), respectively, are reported. These energies correspond in turn to 51% and 57% of the surface bonding energy measured in unpatterned regions on the same samples, i.e. the proportion of unetched Si surface in the patterned areas. The results show that bonding on patterned surfaces can be as robust as on unpatterned surfaces, provided care is taken with the post-patterning surface preparation process and, therefore, open the path towards innovative designs that include patterns embedded in the Si guiding layer of hybrid III-V/Si photonic integrated circuits. PMID:26878333

  3. Average bond energies between boron and elements of the fourth, fifth, sixth, and seventh groups of the periodic table

    NASA Technical Reports Server (NTRS)

    Altshuller, Aubrey P

    1955-01-01

    The average bond energies D(gm)(B-Z) for boron-containing molecules have been calculated by the Pauling geometric-mean equation. These calculated bond energies are compared with the average bond energies D(exp)(B-Z) obtained from experimental data. The higher values of D(exp)(B-Z) in comparison with D(gm)(B-Z) when Z is an element in the fifth, sixth, or seventh periodic group may be attributed to resonance stabilization or double-bond character.

  4. Explosive bonding of metal-matrix composites

    NASA Technical Reports Server (NTRS)

    Reece, O. Y.

    1969-01-01

    Explosive bonding process produces sheet composites of aluminum alloy reinforced by high-strength stainless steel wires. The bonds are excellent metallurgically, no external heat is required, various metals can be bonded, and the process is inexpensive.

  5. 27 CFR 25.96 - Superseding bond.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... approving the superseding bond, will issue a notice of termination for the superseded bond under the provisions of this subpart. Superseding bonds will show the current date of execution and their...

  6. 27 CFR 25.96 - Superseding bond.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... approving the superseding bond, will issue a notice of termination for the superseded bond under the provisions of this subpart. Superseding bonds will show the current date of execution and their...

  7. 27 CFR 25.96 - Superseding bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... approving the superseding bond, will issue a notice of termination for the superseded bond under the provisions of this subpart. Superseding bonds will show the current date of execution and their...

  8. 27 CFR 25.96 - Superseding bond.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... approving the superseding bond, will issue a notice of termination for the superseded bond under the provisions of this subpart. Superseding bonds will show the current date of execution and their...

  9. Silox hydrides (silox = t-Bu/sub 3/SiO. pi. ) of group 5: do ((silox)/sub 2/MH/sub 2/)/sub 2/ (M = Nb, Ta) complexes contain unbridged M-M bonds

    SciTech Connect

    LaPointe, R.E.; Wolczanski, P.T.

    1986-06-11

    Complexes containing M-H bonds are widely recognized as being important intermediates in numerous catalytic processes. Investigations of early metal hydride reactivity have resulted in reagents useful in organic synthesis and modeling studies relevant to the Fischer-Tropsch process. A variety of group 5 hydrides have been described; the majority contain ancillary phosphine and/or cyclopentadienyl ligands that tend to electronically and sterically saturate the early metal center. By introducing an ancillary ligand system with electronic properties dissimilar to the a atforementioned strong sigma-donors, the reactivity and structural properties common to these metal hydrides may be altered. Reported herein are syntheses and selected reactions of group 5 hydrides ligated by tri-tert-butylsiloxide (t-Bu/sub 3/SiO/sup -/, silox), which has been shown to sterically saturate metal centers while leaving them electron deficient.

  10. Evaluation of Microleakage of Dental Composites Using Bonding Agents with Different Placement Techniques: An Invitro Study

    PubMed Central

    Kaur, Jasvir; Garg, Deepanshu; Sunil, MK; Sawhney, Anshul; Malaviya, Neha; Tripathi, Shashank; Arora, Saloni

    2015-01-01

    Background The rapid progress of adhesive dentistry over the past decade has been attributed to the significant advances in dentin bonding technology. Requirements of an ideal bonding agent are quite similar to those indicated by Buonocore despite of many improvements. As we enter the new millennium, it is important for us to examine the past. Objective To evaluate the microleakage of three bonding agents namely Single Bond, Prime & Bond NT and Excite using different composite materials namely Z100, Spectrum TPH, Tetric with three different placement techniques. Materials and Methods Fifty four extracted human premolars were taken & divided into 9 groups depending upon application of bonding agents followed by composite restorations. Specimens were subjected to thermal cycling at 60C, 370C, 540C and again at 370C & then placed in 10 ml each of freshly prepared 50% silver nitrate solution for 2 hour in darkness, washed & placed under sun light for 24 hours. The sectioned specimens were then observed under stereomicroscope to detect microleakage. Results On comparing the mean microleakage scores among the three groups, maximum microleakage scores have been obtained when no bonding agent was used, while least microleakage scores were obtained with double coat of bonding agent. Conclusion The present study suggests that the placement of bonding agent technique before composite restoration can be effective to limit the microleakage at the tooth restoration interface. PMID:26501015

  11. Low temperature GRISM direct bonding

    NASA Astrophysics Data System (ADS)

    Kalkowski, Gerhard; Harnisch, Gerd; Grabowski, Kevin; Benkenstein, Tino; Ehrhardt, Sascha; Zeitner, Uwe; Risse, Stefan

    2015-09-01

    For spectroscopy in space, GRISM elements -obtained by patterning gratings on a prism surface - are gaining increasing interest. Originally developed as dispersive elements for insertion into an imaging light path without deflecting the beam, they are progressively found in sophisticated multi stage dispersion optics. We report on GRISM manufacturing by joining the individual functional elements -prisms and gratings - to suitable components. Fused silica was used as glass material and the gratings were realized by e-beam lithography und dry etching. Alignment of the grating dispersion direction to the prism angle was realized by passive adjustment. Materials adapted bonds of high transmission, stiffness and strength were obtained at temperatures of about 200°C in vacuum by hydrophilic direct bonding. Examples for bonding uncoated as well as coated fused silica surfaces are given. The results illustrate the great potential of hydrophilic glass direct bonding for manufacturing transmission optics to be used under highly demanding environmental conditions, as typical in space.

  12. A conceptual framework of bonding.

    PubMed

    Gay, J

    1981-01-01

    Nurses involved in maternal-infant child care should objectively analyze any tools that purport to measure attachment and/or bonding. Has the author adequately defined the terms? Are directions given for making concepts operational for the practicing nurse? What are the foundations for placing values on parental behaviors? Do deviant parental behaviors reflect poor attachment or bonding, or are such behaviors merely indicative of limited parental opportunities for acquaintance? The presentation of of any conceptual framework should not be considered complete without empirical testing. Such testing and peer critique of a framework are essential fro any theory of bonding to evolve. With further research into the parental-child relationship, nurses can learn to provide adequate care for facilitating the bonding process in families. PMID:6913616

  13. Criteria for Establishing Bond Ratings.

    ERIC Educational Resources Information Center

    Ackerman, Freda Stern

    1984-01-01

    An executive of Moody's Investors Service explains what past experience has taught the company about municipal analysis, how a bond issue is assigned a credit rating, and what issuers can do to obtain the best rating. (MLF)

  14. Hydrogen bond cooperativity and anticooperativity within the water hexamer.

    PubMed

    Guevara-Vela, José Manuel; Romero-Montalvo, Eduardo; Mora Gómez, Víctor Arturo; Chávez-Calvillo, Rodrigo; García-Revilla, Marco; Francisco, Evelio; Pendás, Ángel Martín; Rocha-Rinza, Tomás

    2016-07-20

    The hydrogen bond (HB), arguably the most important non-covalent interaction in chemistry, is getting renewed attention particularly in materials engineering. We address herein HB non-additive features by examining different structures of the water hexamer (cage, prism, book, bag and ring). To that end, we rely on the interacting quantum atoms (IQA) topological energy partition, an approach that has been successfully used to study similar effects in smaller water clusters (see Chem. - Eur. J., 19, 14304). Our IQA interaction energies, , are used to classify the strength of HBs in terms of the single/double character of the donor and acceptor H2O molecules involved in the interaction. The strongest hydrogen bonds on this new scale entail double donors and acceptors that show larger values of than those observed in homodromic cycles, paradigms of cooperative effects. Importantly, this means that besides the traditional HB anticooperativity ascribed to double acceptors and donors, the occurrence of these species is also related to HB strengthening. Overall, we hope that the results of this research will lead to a further understanding of the HB non-additivity in intramolecular and intermolecular interactions. PMID:27149337

  15. Surface analysis in composite bonding

    NASA Technical Reports Server (NTRS)

    Messick, D. L.; Wightman, J. P.

    1983-01-01

    X ray photoelectron spectroscopy and contact angle measurements on graphite fiber composites pretreated in a number of different ways including mechanical, chemical, and light irradiation were analyzed. Data acquired on surface contamination as a result of fabrication techniques provides answers to the strength and durability of adhesively bonded composites. These techniques were shown to provide valuable information on surface analysis of pretreated composites prior to adhesive bonding and following lap shear fracture.

  16. Method to improve commercial bonded SOI material

    DOEpatents

    Maris, Humphrey John; Sadana, Devendra Kumar

    2000-07-11

    A method of improving the bonding characteristics of a previously bonded silicon on insulator (SOI) structure is provided. The improvement in the bonding characteristics is achieved in the present invention by, optionally, forming an oxide cap layer on the silicon surface of the bonded SOI structure and then annealing either the uncapped or oxide capped structure in a slightly oxidizing ambient at temperatures greater than 1200.degree. C. Also provided herein is a method for detecting the bonding characteristics of previously bonded SOI structures. According to this aspect of the present invention, a pico-second laser pulse technique is employed to determine the bonding imperfections of previously bonded SOI structures.

  17. The Chemical Bond in C2.

    PubMed

    Hermann, Markus; Frenking, Gernot

    2016-03-14

    Quantum chemical calculations using the complete active space of the valence orbitals have been carried out for Hn CCHn (n=0-3) and N2 . The quadratic force constants and the stretching potentials of Hn CCHn have been calculated at the CASSCF/cc-pVTZ level. The bond dissociation energies of the C-C bonds of C2 and HC≡CH were computed using explicitly correlated CASPT2-F12/cc-pVTZ-F12 wave functions. The bond dissociation energies and the force constants suggest that C2 has a weaker C-C bond than acetylene. The analysis of the CASSCF wavefunctions in conjunction with the effective bond orders of the multiple bonds shows that there are four bonding components in C2 , while there are only three in acetylene and in N2 . The bonding components in C2 consist of two weakly bonding σ bonds and two electron-sharing π bonds. The bonding situation in C2 can be described with the σ bonds in Be2 that are enforced by two π bonds. There is no single Lewis structure that adequately depicts the bonding situation in C2 . The assignment of quadruple bonding in C2 is misleading, because the bond is weaker than the triple bond in HC≡CH. PMID:26756311

  18. Dynamics of Double Stochastic Operators

    NASA Astrophysics Data System (ADS)

    Saburov, Mansoor

    2016-03-01

    A double stochastic operator is a generalization of a double stochastic matrix. In this paper, we study the dynamics of double stochastic operators. We give a criterion for a regularity of a double stochastic operator in terms of absences of its periodic points. We provide some examples to insure that, in general, a trajectory of a double stochastic operator may converge to any interior point of the simplex.

  19. Double Emulsion Templated Celloidosomes

    NASA Astrophysics Data System (ADS)

    Arriaga, Laura R.; Marquez, Samantha M.; Kim, Shin-Hyun; Chang, Connie; Wilking, Jim; Monroy, Francisco; Marquez, Manuel; Weitz, David A.

    2012-02-01

    We present a novel approach for fabricating celloidosomes, which represent a hollow and spherical three-dimensional self-assembly of living cells encapsulating an aqueous core. Glass- capillary microfluidics is used to generate monodisperse water-in-oil-in-water double emulsion templates using lipids as stabilizers. Such templates allow for obtaining single but also double concentric celloidosomes. In addition, after a solvent removal step the double emulsion templates turn into monodisperse lipid vesicles, whose membrane spontaneously phase separates when choosing the adequate lipid composition, providing the adequate scaffold for fabricating Janus-celloidosomes. These structures may find applications in the development of bioreactors in which the synergistic effects of two different types of cells selectively adsorbed on one of the vesicle hemispheres may be exploited.

  20. Tracking The Double Eagle

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Last summer a trio of aeronauts made aviation history. Ben Abruzzo, Maxie Anderson and Larry Newman, all of Albuquerque, New Mexico, piloted their balloon Double Eagle I1 from Presque Isle, Maine to Miserey, France, some 50 miles from Paris. They were the first to negotiate a successful Atlantic crossing in a freeflying balloon after a score of attempts over a span of more than a century. A year earlier, Abruzzo and Anderson had made an unsuccessful try in their predecessor balloon Double Eagle. On that occasion, a NASA-developed satellite beacon helped save their lives. Carried aboard the balloon, the simple, seven-pound beacon continuously transmitted signals to NASA's Nimbus-6 satellite. Nimbus relayed the signals to monitors at Goddard Space Flight Center, enabling Goddard to compute the balloon's position. Position reports were then telephoned regularly to Double Eagle's control center at Bedford, Massachusetts. This monitoring system proved invaluable when the balloon encountered trouble several days after liftoff.

  1. Double face sealing device

    NASA Technical Reports Server (NTRS)

    Weddendorf, Bruce C. (Inventor)

    1991-01-01

    A double face sealing device for mounting between two surfaces to provide an airtight and fluid-tight seal between a closure member bearing one of the surfaces and a structure or housing bearing the other surface which extends around the opening or hatchway to be closed. The double face sealing device includes a plurality of sections or segments mounted to one of the surfaces, each having a main body portion, a pair of outwardly extending and diverging, cantilever, spring arms, and a pair of inwardly extending and diverging, cantilever, spring arms, an elastomeric cover on the distal, free, ends of the outwardly extending and diverging spring arms, and an elastomeric cover on the distal, free, ends of the inwardly extending and diverging spring arms. The double face sealing device has application or use in all environments requiring a seal, but is particularly useful to seal openings or hatchways between compartments of spacecraft or aircraft.

  2. Design friendly double patterning

    NASA Astrophysics Data System (ADS)

    Yesilada, Emek

    2012-03-01

    Double patterning using 193nm immersion has been adapted as the solution to enable 2x nm technology nodes until the arrival of EUV tools. As a result the past few years have seen a huge effort in creating double patterning friendly design flows. These flows have so far proposed a combination of decomposition rules at cell level and/or at placement level as well as sophisticated decomposition tools with varying density, design iteration and decomposition complexity penalties. What is more, designers have to familiarize themselves with double patterning challenges and decomposition tools. In this paper an alternative approach is presented that allows the development of dense standard cells with minimal impact on design flow due to double patterning. A real case study is done on 20nm node first metal layer where standard cells are designed without considering decomposition restrictions. The resulting layout is carefully studied in order to establish decomposition or color rules that can map the layout into two masks required for double patterning but without the need of complex coloring algorithms. Since the rules are derived from a decomposition unaware design they do not in return impose heavy restrictions on the design at the cell or placement level and show substantial density gains compared to previously proposed methods. Other key advantages are a simplified design flow without complex decomposition tools that can generate a faster time to market solution all at the same time keeping designers isolated from the challenges of the double patterning. The derived design rules highlight process development path required for design driven manufacturing.

  3. Double Bragg Interferometry.

    PubMed

    Ahlers, H; Müntinga, H; Wenzlawski, A; Krutzik, M; Tackmann, G; Abend, S; Gaaloul, N; Giese, E; Roura, A; Kuhl, R; Lämmerzahl, C; Peters, A; Windpassinger, P; Sengstock, K; Schleich, W P; Ertmer, W; Rasel, E M

    2016-04-29

    We employ light-induced double Bragg diffraction of delta-kick collimated Bose-Einstein condensates to create three symmetric Mach-Zehnder interferometers. They rely on (i) first-order, (ii) two successive first-order, and (iii) second-order processes which demonstrate the scalability of the corresponding momentum transfer. With respect to devices based on conventional Bragg scattering, these symmetric interferometers double the scale factor and feature a better suppression of noise and systematic uncertainties intrinsic to the diffraction process. Moreover, we utilize these interferometers as tiltmeters for monitoring their inclination with respect to gravity. PMID:27176520

  4. Double Bragg Interferometry

    NASA Astrophysics Data System (ADS)

    Ahlers, H.; Müntinga, H.; Wenzlawski, A.; Krutzik, M.; Tackmann, G.; Abend, S.; Gaaloul, N.; Giese, E.; Roura, A.; Kuhl, R.; Lämmerzahl, C.; Peters, A.; Windpassinger, P.; Sengstock, K.; Schleich, W. P.; Ertmer, W.; Rasel, E. M.

    2016-04-01

    We employ light-induced double Bragg diffraction of delta-kick collimated Bose-Einstein condensates to create three symmetric Mach-Zehnder interferometers. They rely on (i) first-order, (ii) two successive first-order, and (iii) second-order processes which demonstrate the scalability of the corresponding momentum transfer. With respect to devices based on conventional Bragg scattering, these symmetric interferometers double the scale factor and feature a better suppression of noise and systematic uncertainties intrinsic to the diffraction process. Moreover, we utilize these interferometers as tiltmeters for monitoring their inclination with respect to gravity.

  5. Double-helix stellarator

    SciTech Connect

    Moroz, P.E.

    1997-09-01

    A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A {approx} 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-{beta} MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications.

  6. Double arch mirror study

    NASA Technical Reports Server (NTRS)

    Vukobratovich, D.; Hillman, D.

    1983-01-01

    The development of a method of mounting light weight glass mirrors for astronomical telescopes compatible with the goals of the Shuttle Infrared Telescope Facility (SIRTF) was investigated. A 20 in. diameter double arch lightweight mirror previously fabricated was modified to use a new mount configuration. This mount concept was developed and fabricated. The mounting concept of the double mounting mirror is outlined. The modifications made to the mirror, fabrication of the mirror mount, and room temperature testing of the mirror and mount and the extension of the mirror and mount concept to a full size (40 in. diameter) primary mirror for SIRTF are discussed.

  7. Energetics of short hydrogen bonds in photoactive yellow protein.

    PubMed

    Saito, Keisuke; Ishikita, Hiroshi

    2012-01-01

    Recent neutron diffraction studies of photoactive yellow protein (PYP) proposed that the H bond between protonated Glu46 and the chromophore [ionized p-coumaric acid (pCA)] was a low-barrier H bond (LBHB). Using the atomic coordinates of the high-resolution crystal structure, we analyzed the energetics of the short H bond by two independent methods: electrostatic pK(a) calculations and a quantum mechanical/molecular mechanical (QM/MM) approach. (i) In the QM/MM optimized geometry, we reproduced the two short H-bond distances of the crystal structure: Tyr42-pCA (2.50 Å) and Glu46-pCA (2.57 Å). However, the H atoms obviously belonged to the Tyr or Glu moieties, and were not near the midpoint of the donor and acceptor atoms. (ii) The potential-energy curves of the two H bonds resembled those of standard asymmetric double-well potentials, which differ from those of LBHB. (iii) The calculated pK(a) values for Glu46 and pCA were 8.6 and 5.4, respectively. The pK(a) difference was unlikely to satisfy the prerequisite for LBHB. (iv) The LBHB in PYP was originally proposed to stabilize the ionized pCA because deprotonated Arg52 cannot stabilize it. However, the calculated pK(a) of Arg52 and QM/MM optimized geometry suggested that Arg52 was protonated on the protein surface. The short H bond between Glu46 and ionized pCA in the PYP ground state could be simply explained by electrostatic stabilization without invoking LBHB. PMID:22173632

  8. Double-Stranded Water on Stepped Platinum Surfaces

    NASA Astrophysics Data System (ADS)

    Kolb, Manuel J.; Farber, Rachael G.; Derouin, Jonathan; Badan, Cansin; Calle-Vallejo, Federico; Juurlink, Ludo B. F.; Killelea, Daniel R.; Koper, Marc T. M.

    2016-04-01

    The interaction of platinum with water plays a key role in (electro)catalysis. Herein, we describe a combined theoretical and experimental study that resolves the preferred adsorption structure of water wetting the Pt(111)-step type with adjacent (111) terraces. Double stranded lines wet the step edge forming water tetragons with dissimilar hydrogen bonds within and between the lines. Our results qualitatively explain experimental observations of water desorption and impact our thinking of solvation at the Pt electrochemical interface.

  9. Water Nucleation on Gold: Existence of a Unique Double Bilayer

    SciTech Connect

    Hrbek, J.; Stacchiola, D.; Park, J.B.; Liu, P.; Ma, S.; Yang, F.; Starr, D.E.; Muller, E.; Sutter, P.

    2009-08-27

    Combining the results from experimental (STM and IRAS) and theoretical (DFT) studies of water adsorption on gold, we show that the Au(111) surface is hydrophobic. The weak interaction of water with Au induces the formation of a unique double bilayer, which itself is hydrophobic due to the internal locking of all hydrogen bonds within the bilayer and between the two bilayers of the water clusters.

  10. Aqueous hydrogen bonding probed with polarization and matrix isolation spectroscopy

    NASA Astrophysics Data System (ADS)

    Shultz, Mary Jane; Bisson, Patrick; Buch, Victoria; Groenzin, Henning; Li, Irene

    2010-05-01

    A major challenge in hydrogen-bond research is interpreting the vibrational spectrum of water, arguably the most fundamental hydrogen bonding system. This challenge remains despite over a half century of progress in vibrational spectroscopy, largely due to a combination of the huge oscillator strength and the enormous width of the hydrogen-bond region. Lack of assignment of the resonances in the hydrogen-bond region hinders investigation of interactions between water and solutes. This lack-of-interpretation issue is an even more significant problem for studies of the aqueous interface. Numerous solutes are known to have an effect, some very dramatic, on the shape of the surface spectrum. These effects, however, are but tantalizing teasers because lack of interpretation means that the changes cannot be used to diagnose the effect of solutes or impinging gas-phase molecules on the surface. In the reported work two techniques are used to probe the origin of vibrational resonances in the H-bonded region: the surface sensitive technique sum frequency generation (SFG) and room-temperature matrix isolation spectroscopy (RT-MIS). A polarization technique called polarization angle null (PAN) has been developed that extends SFG and enables identification of resonances. The result of applying PAN-SFG to single crystal, I h ice is identification of at least nine underlying resonances and assignment of two of these. One resonance is correlated with the crystal temperature and is a sensitive probe for interactions that disrupt long range order on the surface - it is a morphology reporter. The second is associated with weakly bonded, double-donor water molecules. This resonance is sensitive to interaction of hydrogen bond donors, i.e. acids, with the surface. Both modes are more correctly pictured as collective modes. These two assignments are the first definitive assignments in the hydrogen-bond region for the aqueous surface. The effect of salts on the vibrational spectrum of

  11. Carbene insertion into a P-H bond: parent phosphinidene-carbene adducts from PH3 and bis(phosphinidene)mercury complexes.

    PubMed

    Bispinghoff, Mark; Tondreau, Aaron M; Grützmacher, Hansjörg; Faradji, Charly A; Pringle, Paul G

    2016-04-14

    PH3 reacts with the in situ generated N-heterocyclic carbene DippNHC* (DippNHC* = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) to give the phosphanyl-imidazolidine [(Dipp)NHC*-H]-[PH2]. Upon treatment with an ortho-quinone, [(Dipp)NHC*-H]-[PH2] is dehydrogenated to give the parent phosphinidene-carbene adduct (Dipp)NHC*[double bond, length as m-dash]PH. Alternative routes to [(Dipp)NHC*-H]-[PH2] and (Dipp)NHC*[double bond, length as m-dash]PH employ NaPH2 and (TMS)3P7 (TMS = trimethylsilyl), respectively, as phosphorus sources. The adduct (Dipp)NHC*[double bond, length as m-dash]PH and the related adduct (Dipp)NHC[double bond, length as m-dash]PH ((Dipp)NHC = bis(2,6-diisopropylphenyl)imidazol-2-ylidene) possessing an unsaturated NHC backbone both react with HgCl2 to give the bis(carbene-phosphinidenyl) complexes [((Dipp)NHC*[double bond, length as m-dash]P)2Hg] and [((Dipp)NHC[double bond, length as m-dash]P)2Hg]. PMID:26122315

  12. Bond length, dipole moment, and harmonic frequency of CO

    NASA Technical Reports Server (NTRS)

    Barnes, Leslie A.; Liu, Bowen; Lindh, Roland

    1993-01-01

    A detailed comparison of some properties of CO is given, at the modified coupled-pair functional, single and double excitation coupled-cluster (CCSD), and CCSD(T) levels of theory (including a perturbational estimate for connected triple excitations), using a variety of basis sets. With very large one-particle basis sets, the CCSD(T) method gives excellent results for the bond distance, dipole moment, and harmonic frequency of CO. In a (6s 5p 4d 3f 2g 1h) + (1s 1p 1d) basis set, the bond distance is about 0.005a0 too large, the dipole moment about 0.005 a.u. too small, and the frequency about 6/cm too small, when compared with experimental results.

  13. Synthesis and characterization of hydrogen-bond acidic functionalized graphene

    NASA Astrophysics Data System (ADS)

    Yang, Liu; Han, Qiang; Pan, Yong; Cao, Shuya; Ding, Mingyu

    2014-05-01

    Hexafluoroisopropanol phenyl group functionalized materials have great potential in the application of gas-sensitive materials for nerve agent detection, due to the formation of strong hydrogen-bonding interactions between the group and the analytes. In this paper, take full advantage of ultra-large specific surface area and plenty of carbon-carbon double bonds and hexafluoroisopropanol phenyl functionalized graphene was synthesized through in situ diazonium reaction between -C=C- and p-hexafluoroisopropanol aniline. The identity of the as-synthesis material was confirmed by transmission electron microscopy, Raman spectroscopy, ultraviolet visible spectroscopy, X-ray photoelectron spectroscopy and thermo gravimetric analysis. The synthesis method is simply which retained the excellent physical properties of original graphene. In addition, the novel material can be assigned as an potential candidate for gas sensitive materials towards organophosphorus nerve agent detection.

  14. Methandiide as a non-innocent ligand in carbene complexes: from the electronic structure to bond activation reactions and cooperative catalysis.

    PubMed

    Becker, Julia; Modl, Tanja; Gessner, Viktoria H

    2014-09-01

    The synthesis of a ruthenium carbene complex based on a sulfonyl-substituted methandiide and its application in bond activation reactions and cooperative catalysis is reported. In the complex, the metal-carbon interaction can be tuned between a Ru-C single bond with additional electrostatic interactions and a Ru=C double bond, thus allowing the control of the stability and reactivity of the complex. Hence, activation of polar and non-polar bonds (O-H, H-H) as well as dehydrogenation reactions become possible. In these reactions the carbene acts as a non-innocent ligand supporting the bond activation as nucleophilic center in the 1,2-addition across the metal-carbon double bond. This metal-ligand cooperativity can be applied in the catalytic transfer hydrogenation for the reduction of ketones. This concept opens new ways for the application of carbene complexes in catalysis. PMID:25047390

  15. "Vibrational bonding": a new type of chemical bond is discovered.

    PubMed

    Rhodes, Christopher J; Macrae, Roderick M

    2015-01-01

    A long-sought but elusive new type of chemical bond, occurring on a minimum-free, purely repulsive potential energy surface, has recently been convincingly shown to be possible on the basis of high-level quantum-chemical calculations. This type of bond, termed a vibrational bond, forms because the total energy, including the dynamical energy of the nuclei, is lower than the total energy of the dissociated products, including their vibrational zero-point energy. For this to be the case, the ZPE of the product molecule must be very high, which is ensured by replacing a conventional hydrogen atom with its light isotope muonium (Mu, mass = 1/9 u) in the system Br-H-Br, a natural transition state in the reaction between Br and HBr. A paramagnetic species observed in the reaction Mu +Br2 has been proposed as a first experimental sighting of this species, but definitive identification remains challenging. PMID:25942773

  16. Double-Glazing Interferometry

    ERIC Educational Resources Information Center

    Toal, Vincent; Mihaylova, Emilia M.

    2009-01-01

    This note describes how white light interference fringes can be seen by observing the Moon through a double-glazed window. White light interferometric fringes are normally observed only in a well-aligned interferometer whose optical path difference is less than the coherence length of the light source, which is approximately one micrometer for…

  17. Rosette (Double Blossom)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rosette, or double blossom, is a serious disease of erect blackberries that is limited to the genus Rubus. Rosette may occur on trailing blackberries and dewberries, but rarely on red and black raspberries. In the United States, rosette occurs from New Jersey to Illinois and southwest to Texas and i...

  18. Double layers without current

    SciTech Connect

    Perkins, F.W.; Sun, Y.C.

    1980-11-01

    The steady-state solution of the nonlinear Vlasov-Poisson equations is reduced to a nonlinear eigenvalue problem for the case of double-layer (potential drop) boundary conditions. Solutions with no relative electron-ion drifts are found. The kinetic stability is discussed. Suggestions for creating these states in experiments and computer simulations are offered.

  19. Double resonator cantilever accelerometer

    DOEpatents

    Koehler, Dale R.

    1984-01-01

    A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

  20. Double resonator cantilever accelerometer

    DOEpatents

    Koehler, D.R.

    1982-09-23

    A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

  1. Double Trouble (Abstract)

    NASA Astrophysics Data System (ADS)

    Simonsen, M.

    2015-12-01

    (Abstract only) Variable stars with close companions can be difficult to accurately measure and characterize. The companions can create misidentifications, which in turn can affect the perceived magnitudes, amplitudes, periods, and colors of the variable stars. We will show examples of these Double Trouble stars and the impact their close companions have had on our understanding of some of these variable stars.

  2. Weathering the Double Whammy.

    ERIC Educational Resources Information Center

    Wellman, Jane V.

    2002-01-01

    Discusses how governing boards can help their institutions weather the "double-whammy" of doing more with less: identify the institution's short-term and long-term challenges; refocus the institution's mission, planning, and programming; assess and integrate the institution's tuition, aid, and outreach strategies; redouble the institution's…

  3. Sun Packs Double Punch

    NASA Video Gallery

    On August 3, the sun packed a double punch, emitting a M6.0-class flare at 9:43 am EDT. This video is of the second, slightly stronger M9.3-class flare at 11:41 pm EDT. Both flares had significant ...

  4. Double-Entry Bookkeeping.

    ERIC Educational Resources Information Center

    Snyder, Herbert

    1999-01-01

    Explains the principles and mechanics of double-entry bookkeeping as a part of the accounting cycle to produce a functioning set of accounting records. Suggests that libraries need to have accurate and timely information about their spending to gain financial control and protect against fraud and abuse. (LRW)

  5. A matterless double slit

    NASA Astrophysics Data System (ADS)

    King, Ben; di Piazza, Antonino; Keitel, Christoph H.

    2010-02-01

    Double slits provide incoming particles with a choice. Those that survive passage through the slits have chosen from two possible paths, which interfere to distribute them in a wave-like manner. Such wave-particle duality continues to be challenged and investigated in a broad range of disciplines with electrons, neutrons, helium atoms, C60 fullerenes, Bose-Einstein condensates and biological molecules. All variants have hitherto involved material constituents. We present a matterless double-slit scenario in which photons generated from virtual electron-positron pair annihilation in head-on collisions of a probe laser field with two ultra-intense laser beams form a double-slit interference pattern. Such electromagnetic fields are predicted to induce material-like behaviour in vacuum, supporting elastic scattering between photons. Our double-slit scenario presents, on the one hand, a realizable method with which to observe photon-photon scattering and, on the other hand, demonstrates the possibility of both controlling light with light and non-locally investigating features of the quantum vacuum structure.

  6. Double Marking Revisited

    ERIC Educational Resources Information Center

    Brooks, Val

    2004-01-01

    In 2002, the Qualifications and Curriculum Authority (QCA) published the report of an independent panel of experts into maintaining standards at Advanced Level (A-Level). One of its recommendations was for: limited experimental double marking of scripts in subjects such as English to determine whether the strategy would significantly reduce errors…

  7. [Double ricochet marks].

    PubMed

    Sellier, K

    1987-01-01

    When bullets are flying stably and ricochet on a surface, only one mark is produced. In contrast yawing bullets can produce a double mark if the angle of incidence is sufficiently small (less than or equal to 5 degrees). Distances up to 15 cm were seen between the two marks. PMID:3660953

  8. Teaching the Double Layer.

    ERIC Educational Resources Information Center

    Bockris, J. O'M.

    1983-01-01

    Suggests various methods for teaching the double layer in electrochemistry courses. Topics addressed include measuring change in absolute potential difference (PD) at interphase, conventional electrode potential scale, analyzing absolute PD, metal-metal and overlap electron PDs, accumulation of material at interphase, thermodynamics of electrified…

  9. Design for Double Rainbow

    ERIC Educational Resources Information Center

    Thomas, Lisa Carlucci

    2011-01-01

    Rare is the inspirational, spontaneous, transformative moment shared among 20 million people. In the summer of 2010, people around the world were moved by the sighting of a double rainbow--almost a triple rainbow--"all the way across the sky" in Yosemite National Park. Caught on video and posted to by YouTube by Paul Vasquez in January 2010, the…

  10. Towards an understanding of the bonding in polyoxometalates through bond order and bond energy analysis.

    PubMed

    Bridgeman, Adam J; Cavigliasso, Germán

    2003-01-01

    The molecular and electronic structures of transition metal complexes, [MOCl5]n- (n = 2 for M = V,Nb,Ta and n = 1 for Mo,W) and mixed-metal polyoxometalates, [M'M5O19]3-V,Nb,Ta, M = Mo,W) containing a single terminal oxo group on each metal, and of complexes of the uranyl ion [UO2]2+, [UO2(H2O)5]2+ and [UO2Cl4]2-, have been calculated using density functional methods. The calculated structures of the complexes are in good agreement with available experimental parameters. For the mixed-metal hexametalates, for which no crystallographic data is available, the calculations predict a small tetragonal compression of the clusters with only minor structural changes compared to the parent molybdate and tungstate. The metal oxygen bonding in these anions has been probed using Mayer-Mulliken, bond energy and atoms in molecule analyses (AIM). These methods provide a consistent description of the bonding in polyoxometalates. The terminal bonds between transition metal or uranium and oxygen atoms have large sigma and pi components with the pi contributions exceeding the sigma bonding. The transition metals utilize their d orbitals almost exclusively to bond to oxygen whilst uranium uses both its 5f and 6d orbitals. Oxygen atom charges increase and covalency indexes decrease with coordination number, with a marked separation of these terms according to the oxygen atom type. The total valency and AIM energies of the oxygen atoms are predicted to be almost constant for all types of oxygen site. The constancy of the bonding power of the oxygen atoms appears to be an important factor in determining the gross structures and details of the bonding in polyoxometalates. The Mayer Mulliken approach provides direct characterization of the bonding power of atoms and the extent of the interaction between pairs of atoms that is consistent with the results of the considerably more computationally demanding bond energy and AIM approaches. PMID:14527219

  11. Dentine and enamel bonding agents.

    PubMed

    Bowen, R L; Tung, M S; Blosser, R L; Asmussen, E

    1987-09-01

    Previous studies have shown that sequential use of aqueous FO (ferric oxalate containing a small concentration of HNO3), acetone solutions of NPG (N-phenylglycine), and PMDM (the reaction product of pyromellitic dianhydride and 2-hydroxyethylmethacrylate) yields strong adhesive bonding of composite resins to both dentine and enamel. The purpose of this study was to determine if aluminum ions could be substituted for ferric ions and if the procedure could be simplified. Aqueous solutions containing aluminum oxalate and aluminum nitrate, followed in sequence by acetone solutions of NPG and PMDM, gave strong tensile adhesive bond strengths between a composite and extracted human teeth. Comparable values have been obtained with FO, NPG and PMDM. Aluminum oxalate solutions containing no nitrate gave lower bond strengths, as was the case with FO. Aqueous solutions of acidified aluminum oxalate can dissolve NPG, thereby allowing a simplification of the procedure. Tested for comparison, commercially available dentine bonding agents gave lower average bond strengths on dentine than did some of the experimental materials. PMID:3316044

  12. Welding, Bonding and Fastening, 1984

    NASA Technical Reports Server (NTRS)

    Buckley, J. D. (Editor); Stein, B. A. (Editor)

    1985-01-01

    A compilation of papers presented in a joint NASA, American Society for Metals, The George Washington University, American Welding Soceity, and Society of Manufacturing Engineers conference on Welding, Bonding, and Fastening at Langley Research Center, Hampton, VA, on October 23 to 25, 1984 is given. Papers were presented on technology developed in current research programs relevant to welding, bonding, and fastening of structural materials required in fabricating structures and mechanical systems used in the aerospace, hydrospace, and automotive industries. Topics covered in the conference included equipment, hardware and materials used when welding, brazing, and soldering, mechanical fastening, explosive welding, use of unique selected joining techniques, adhesives bonding, and nondestructive evaluation. A concept of the factory of the future was presented, followed by advanced welding techniques, automated equipment for welding, welding in a cryogenic atmosphere, blind fastening, stress corrosion resistant fasteners, fastening equipment, explosive welding of different configurations and materials, solid-state bonding, electron beam welding, new adhesives, effects of cryogenics on adhesives, and new techniques and equipment for adhesive bonding.

  13. Transient liquid phase ceramic bonding

    DOEpatents

    Glaeser, Andreas M.

    1994-01-01

    Ceramics are joined to themselves or to metals using a transient liquid phase method employing three layers, one of which is a refractory metal, ceramic or alloy. The refractory layer is placed between two metal layers, each of which has a lower melting point than the refractory layer. The three layers are pressed between the two articles to be bonded to form an assembly. The assembly is heated to a bonding temperature at which the refractory layer remains solid, but the two metal layers melt to form a liquid. The refractory layer reacts with the surrounding liquid and a single solid bonding layer is eventually formed. The layers may be designed to react completely with each other and form refractory intermetallic bonding layers. Impurities incorporated into the refractory metal may react with the metal layers to form refractory compounds. Another method for joining ceramic articles employs a ceramic interlayer sandwiched between two metal layers. In alternative embodiments, the metal layers may include sublayers. A method is also provided for joining two ceramic articles using a single interlayer. An alternate bonding method provides a refractory-metal oxide interlayer placed adjacent to a strong oxide former. Aluminum or aluminum alloys are joined together using metal interlayers.

  14. Immediate bonding to bleached enamel.

    PubMed

    Nour El-din, Amal K; Miller, Barbara H; Griggs, Jason A; Wakefield, Charles

    2006-01-01

    This research sought to determine the shear bond strength, degree of resin infiltration and failure mode when organic solvent-based adhesives (acetone or ethanol) were used in immediate bonding to enamel bleached with 10% carbamide peroxide or 38% hydrogen peroxide systems. Seventy-two non-carious bovine incisors were randomly assigned to three groups of 24 specimens each-control group (deionized water), 38% hydrogen peroxide bleach group and 10% carbamide peroxide bleach group. Each group was further subdivided into two subgroups of 12 specimens each according to the adhesive system used to bond the resin composite to enamel surfaces. The two adhesive systems used were Single Bond, an ethanol-based adhesive, and One Step, an acetone-based adhesive. The shear bond strengths of 38% hydrogen peroxide and 10% carbamide peroxide were significantly lower compared to the non-bleached controls. Fractography revealed an adhesive failure mode in all specimens. Qualitative comparisons of resin tags present in the bleached and unbleached specimens using scanning electron microscopy (SEM) revealed few, thin and fragmented resin tags when 38% hydrogen peroxide and 10% carbamide peroxide were used. PMID:16536201

  15. The behavior of bonded doubler splices for composite sandwich panels

    NASA Technical Reports Server (NTRS)

    Zeller, T. A.; Weisahaar, T. A.

    1980-01-01

    The results of an investigation into the behavior of adhesively bonded doubler splices of two composite material sandwich panels are presented. The splices are studied from three approaches: analytical; numerical (finite elements); and experimental. Several parameters that characterize the splice are developed to determine their influence upon joint strength. These parameters are: doubler overlap length; core stiffness; laminate bending stiffness; the size of the gap between the spliced sandwich panels; and room and elevated temperatures. Similarities and contrasts between these splices and the physically similar single and double lap joints are discussed. The results of this investigation suggest several possible approaches to improving the strength of the sandwich splices.

  16. 21 CFR 1005.23 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Bonds. 1005.23 Section 1005.23 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) RADIOLOGICAL HEALTH IMPORTATION OF ELECTRONIC PRODUCTS Bonding and Compliance Procedures § 1005.23 Bonds. The bond required...

  17. 21 CFR 1005.23 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Bonds. 1005.23 Section 1005.23 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) RADIOLOGICAL HEALTH IMPORTATION OF ELECTRONIC PRODUCTS Bonding and Compliance Procedures § 1005.23 Bonds. The bond required under section 360(b) of the Act shall...

  18. 21 CFR 1005.23 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Bonds. 1005.23 Section 1005.23 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) RADIOLOGICAL HEALTH IMPORTATION OF ELECTRONIC PRODUCTS Bonding and Compliance Procedures § 1005.23 Bonds. The bond required...

  19. 21 CFR 1005.23 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Bonds. 1005.23 Section 1005.23 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) RADIOLOGICAL HEALTH IMPORTATION OF ELECTRONIC PRODUCTS Bonding and Compliance Procedures § 1005.23 Bonds. The bond required...

  20. 21 CFR 1005.23 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Bonds. 1005.23 Section 1005.23 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) RADIOLOGICAL HEALTH IMPORTATION OF ELECTRONIC PRODUCTS Bonding and Compliance Procedures § 1005.23 Bonds. The bond required...

  1. 27 CFR 19.516 - Bond account.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... maximum penal sum, he shall maintain an account of his bond and he shall charge the bond with the amount... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bond account. 19.516... Determination and Payment of Tax § 19.516 Bond account. Where the proprietor has furnished a withdrawal or...

  2. Oregon School Bond Manual. Sixth Edition.

    ERIC Educational Resources Information Center

    Oregon State Dept. of Education, Salem. Office of School District Services.

    Given that purchasers of Oregon school bonds rely on recommendations of accredited bond attorneys, this document is designed to assist school districts in complying with state statutes regulating the issuance of school bond issues in order that attorney opinions may be favorable. Six initial steps toward a bond sale and Oregon laws regarding bonds…

  3. 46 CFR Sec. 2 - Amount of bond.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 8 2010-10-01 2010-10-01 false Amount of bond. Sec. 2 Section 2 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION A-NATIONAL SHIPPING AUTHORITY BONDING OF SHIP'S PERSONNEL Sec. 2 Amount of bond. The amount of the bond must be governed by the amount of monies advanced or value of...

  4. 46 CFR Sec. 2 - Amount of bond.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 8 2011-10-01 2011-10-01 false Amount of bond. Sec. 2 Section 2 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION A-NATIONAL SHIPPING AUTHORITY BONDING OF SHIP'S PERSONNEL Sec. 2 Amount of bond. The amount of the bond must be governed by the amount of monies advanced or value of...

  5. 46 CFR Sec. 4 - Posting of bond.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 8 2011-10-01 2011-10-01 false Posting of bond. Sec. 4 Section 4 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION A-NATIONAL SHIPPING AUTHORITY BONDING OF SHIP'S PERSONNEL Sec. 4 Posting of bond. The General Agent shall retain an executed copy of each such bond in its principal...

  6. 46 CFR Sec. 4 - Posting of bond.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 8 2010-10-01 2010-10-01 false Posting of bond. Sec. 4 Section 4 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION A-NATIONAL SHIPPING AUTHORITY BONDING OF SHIP'S PERSONNEL Sec. 4 Posting of bond. The General Agent shall retain an executed copy of each such bond in its principal...

  7. 43 CFR 3474.1 - Bonding requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Bonding requirements. 3474.1 Section 3474....1 Bonding requirements. (a) Before a lease may be issued, one of the following forms of lease bond... a form approved by the Director. (c) The bonding obligation for a new lease may be met by...

  8. 27 CFR 24.146 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    .... (c) Wine vinegar plant bond. The proprietor of a wine vinegar plant who withdraws wine from a bonded wine premises without payment of tax for use in the manufacture of vinegar shall file a bond on TTB F 5510.2, Bond Covering Removal to and Use of Wine at Vinegar Plant, to ensure the payment of the tax...

  9. 27 CFR 24.146 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    .... (c) Wine vinegar plant bond. The proprietor of a wine vinegar plant who withdraws wine from a bonded wine premises without payment of tax for use in the manufacture of vinegar shall file a bond on TTB F 5510.2, Bond Covering Removal to and Use of Wine at Vinegar Plant, to ensure the payment of the tax...

  10. 27 CFR 24.146 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... (c) Wine vinegar plant bond. The proprietor of a wine vinegar plant who withdraws wine from a bonded wine premises without payment of tax for use in the manufacture of vinegar shall file a bond on TTB F 5510.2, Bond Covering Removal to and Use of Wine at Vinegar Plant, to ensure the payment of the tax...

  11. 27 CFR 24.146 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    .... (c) Wine vinegar plant bond. The proprietor of a wine vinegar plant who withdraws wine from a bonded wine premises without payment of tax for use in the manufacture of vinegar shall file a bond on TTB F 5510.2, Bond Covering Removal to and Use of Wine at Vinegar Plant, to ensure the payment of the tax...

  12. 27 CFR 24.146 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    .... (c) Wine vinegar plant bond. The proprietor of a wine vinegar plant who withdraws wine from a bonded wine premises without payment of tax for use in the manufacture of vinegar shall file a bond on TTB F 5510.2, Bond Covering Removal to and Use of Wine at Vinegar Plant, to ensure the payment of the tax...

  13. 36 CFR 228.51 - Bonding.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 2 2013-07-01 2013-07-01 false Bonding. 228.51 Section 228.51 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE MINERALS Disposal of Mineral Materials General Provisions § 228.51 Bonding. (a) Bond requirements. Before operations may begin under any contract or permit, a bond...

  14. Pet Bonding and Pet Bereavement among Adolescents.

    ERIC Educational Resources Information Center

    Brown, Brenda H.; And Others

    1996-01-01

    Studied adolescent-pet bonding and bereavement following pet loss (n=55). Hypothesized that highly-bonded adolescents experience more intense grief when a pet dies than do those less bonded; degree of bonding is greater for girls than for boys; and intensity of bereavement is greater for girls than for boys. Results supported the hypotheses. (RB)

  15. How School District Bonds Are Rated.

    ERIC Educational Resources Information Center

    Hitchcock, David

    1992-01-01

    Bond ratings are an assessment by an independent rating agency of the credit worthiness of a bond issuer, such as a school district, on repayment of a particular bond issue. Describes the rating procedures Standard and Poor's Municipal Finance Department uses to assign bond ratings. (MLF)

  16. 43 CFR 3104.1 - Bond obligations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Bond obligations. 3104.1 Section 3104.1..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) OIL AND GAS LEASING Bonds § 3104.1 Bond obligations. (a..., operating rights owner (sublessee), or operator shall submit a surety or a personal bond, conditioned...

  17. 43 CFR 3104.1 - Bond obligations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Bond obligations. 3104.1 Section 3104.1..., DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) OIL AND GAS LEASING Bonds § 3104.1 Bond obligations. (a..., operating rights owner (sublessee), or operator shall submit a surety or a personal bond, conditioned...

  18. 27 CFR 25.96 - Superseding bond.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Superseding bond. 25.96 Section 25.96 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT... principal submits a new bond to supersede a bond or bonds in effect, the appropriate TTB officer,...

  19. Ceric ammonium nitrate (CAN) catalyzed modification of ketones via two C-C bond cleavages with the retention of the oxo-group.

    PubMed

    Feng, Peng; Sun, Xiang; Su, Yijin; Li, Xinyao; Zhang, Li He; Shi, Xiaodong; Jiao, Ning

    2014-06-20

    A simple ceric ammonium nitrate (CAN) catalyzed functionalization of ketones through double C-C bond cleavage strategy has been disclosed. This reaction provides a mild, practical method toward carbamoyl azides, which are versatile intermediates and building blocks in organic synthesis. Based on relevant mechanistic studies, a unique and plausible C-C bond and N-O bond cleavage process is proposed, where the oxyamination intermediate plays an important role in this reaction. PMID:24906031

  20. Three methods to measure RH bond energies

    SciTech Connect

    Berkowitz, J.; Ellison, G.B.; Gutman, D.

    1993-03-21

    In this paper the authors compare and contrast three powerful methods for experimentally measuring bond energies in polyatomic molecules. The methods are: radical kinetics; gas phase acidity cycles; and photoionization mass spectroscopy. The knowledge of the values of bond energies are a basic piece of information to a chemist. Chemical reactions involve the making and breaking of chemical bonds. It has been shown that comparable bonds in polyatomic molecules, compared to the same bonds in radicals, can be significantly different. These bond energies can be measured in terms of bond dissociation energies.

  1. Catch bonds: physical models and biological functions.

    PubMed

    Zhu, Cheng; McEver, Rodger P

    2005-09-01

    Force can shorten the lifetimes of receptor-ligand bonds by accelerating their dissociation. Perhaps paradoxical at first glance, bond lifetimes can also be prolonged by force. This counterintuitive behavior was named catch bonds, which is in contrast to the ordinary slip bonds that describe the intuitive behavior of lifetimes being shortened by force. Fifteen years after their theoretical proposal, catch bonds have finally been observed. In this article we review recently published data that have demonstrated catch bonds in the selectin system and suggested catch bonds in other systems, the theoretical models for their explanations, and their function as a mechanism for flow-enhanced adhesion. PMID:16708472

  2. Rhodium-catalyzed C-C coupling reactions via double C-H activation.

    PubMed

    Li, Shuai-Shuai; Qin, Liu; Dong, Lin

    2016-05-18

    Various rhodium-catalyzed double C-H activations are reviewed. These powerful strategies have been developed to construct C-C bonds, which might be widely embedded in complex aza-fused heterocycles, polycyclic skeletons and heterocyclic scaffolds. In particular, rhodium(iii) catalysis shows good selectivity and reactivity to functionalize the C-H bond, generating reactive organometallic intermediates in most of the coupling reactions. Generally, intermolecular, intramolecular and multi-component coupling reactions via double C-H activations with or without heteroatom-assisted chelation are discussed in this review. PMID:27099126

  3. Ultrasonic Bonding of Solar-Cell Leads

    NASA Technical Reports Server (NTRS)

    Frasch, W.

    1984-01-01

    Rolling ultrasonic spot-bonding method successfully joins aluminum interconnect fingers to silicon solar cells with copper metalization. Technique combines best features of ultrasonic rotary seam welding and ultrasonic spot bonding: allows fast bond cycles and high indexing speeds without use of solder or flux. Achieves reliable bonds at production rates without damage to solar cells. Bonding system of interest for all solar-cell assemblies and other assemblies using flat leads (rather than round wires).

  4. Double Degrees: Double the Trouble or Twice the Return?

    ERIC Educational Resources Information Center

    Russell, A. Wendy; Dolnicar, Sara; Ayoub, Marina

    2008-01-01

    Double degrees (also called joint or combined degrees)--programs of study combining two bachelor degrees--are increasingly popular in Australian universities, particularly among women. A case study using qualitative and quantitative surveys of current and past double degree students is presented. The study indicates that double degrees benefit…

  5. To Bond or Not to Bond? That Is the Question

    ERIC Educational Resources Information Center

    Balzer, Wayne E.

    2015-01-01

    This case, inspired by a real school district scenario, was developed for use in a graduate-level course in school finance. James Spencer had just been selected as the new superintendent of a low-income, 400-student, rural school district in need of many capital improvements. The previous superintendent had refused to hold a bond election because…

  6. Probing the Hydrogen Bond Strength at Single Bond Limit

    NASA Astrophysics Data System (ADS)

    Guo, Jing; Lü, Jing-Tao; Chen, Ji; Peng, Jinbo; Meng, Xiangzhi; Wang, Zhichang; Li, Xin-Zheng; Wang, Enge; Jiang, Ying

    2015-03-01

    Many extraordinary physical, chemical and biological properties of water are determined by hydrogen-bonding interaction between the water molecules. So far, the routine way to determine the hydrogen-bonding strength of water is probing the frequency shift of O-H stretching mode using various spectroscopic techniques, which all suffer from the difficulty of spectral assignment and the broadening of vibrational signals due to the lack of spatial resolution. In this talk, we show the ability to probe the hydrogen-bonding strength of interfacial water at single bond limit using resonantly enhanced inelastic electron tunneling spectroscopy (IETS) with a scanning tunneling microscope (STM). The conventional IET signals of water molecules are extremely weak and far beyond the experimental detection limit due to the negligible molecular density of states (DOS) around the Fermi level. This difficulty can be surmounted by turning on the tip-water coupling, which shifts and broadens the frontier molecular orbitals of water to the proximity of Fermi level, resulting in a resonantly enhanced IET process. International Center for Quantum Materials, School of Physics, Peking University.

  7. Catch-bond behavior of bacteria binding by slip bonds.

    PubMed

    Björnham, Oscar; Axner, Ove

    2010-09-01

    It is shown that multipili-adhering bacteria expressing helix-like pili binding by slip bonds can show catch-bond behavior. When exposed to an external force, such bacteria can mediate adhesion to their hosts by either of two limiting means: sequential or simultaneous pili force exposure (referring to when the pili mediate force in a sequential or simultaneous manner, respectively). As the force is increased, the pili can transition from sequential to simultaneous pili force exposure. Since the latter mode of adhesion gives rise to a significantly longer bacterial adhesion lifetime than the former, this results in a prolongation of the lifetime, which shows up as a catch-bond behavior. The properties and conditions of this effect were theoretically investigated and assessed in some detail for dual-pili-adhering bacteria, by both analytical means and simulations. The results indicate that the adhesion lifetime of such bacteria can be prolonged by more than an order of magnitude. This implies that the adhesion properties of multibinding systems cannot be directly conveyed to the individual adhesion-receptor bonds. PMID:20816044

  8. Hydrogen Bonds in Polymer Folding

    NASA Astrophysics Data System (ADS)

    Borg, Jesper; Jensen, Mogens H.; Sneppen, Kim; Tiana, Guido

    2001-02-01

    We studied the thermodynamics of a homopolymeric chain with both van der Waals and directed hydrogen bond interaction. The effect of hydrogen bonds is to reduce dramatically the entropy of low-lying states and to give rise to long-range order and to conformations displaying secondary structures. For compact polymers a transition is found between helix-rich states and low-entropy sheet-dominated states. The consequences of this transition for protein folding and, in particular, for the problem of prions are discussed.

  9. Anodic bonding using a hybrid electrode with a two-step bonding process

    NASA Astrophysics Data System (ADS)

    Wei, Luo; Jing, Xie; Yang, Zhang; Chaobo, Li; Yang, Xia

    2012-06-01

    A two-step bonding process using a novel hybrid electrode is presented. The effects of different electrodes on bonding time, bond strength and the bonded interface are analyzed. The anodic bonding is studied using a domestic bonding system, which carries out a detailed analysis of the integrity of the bonded interface and the bond strength measurement. With the aid of the hybrid electrode, a bubble-free anodic bonding process could be accomplished within 15-20 min, with a shear strength in excess of 10 MPa. These results show that the proposed method has a high degree of application value, including in most wafer-level MEMS packaging.

  10. Fluxless flip chip bonding processes and aerial fluxless bonding technology

    NASA Astrophysics Data System (ADS)

    Kim, Dongwook

    New fluxless flip chip processes of Sn-rich non-eutectic Au-Sn solder bumps were developed using vacuum deposition and electroplating technique. It is believed that this is the first report that non-eutectic Au-Sn flip chip solder bonding is achieved without the use of flux. In order to make 200mum diameter and 10mum thick Au-Sn solder bump 0.03mum of Cr, 10mum of Sn and 0.3mum of Au were vacuum deposited on the Si wafer through the high carbon steal stencil mask. Nearly void-free solder bumps with small grains of AuSn4 intermetallic compound were achieved. The re-melting temperature of solder bumps was measured to be 220°C. In the second part, first, the fluxless bonding process was performed in hydrogen environment with electroplated 4 mm x 4mm Au-Sn multi-layer chips if electroplating technique is compatible with our process. High quality and nearly void free solder joint was successfully achieved with this new process. After proving compatibility of the process, tall electroplated Sn/Au bumps (50 mum) were produced by photolithography method using Su-8 photoresist. The bumps in the chip were flip chip bonded to the borosilicate glass wafer coated with Cr (0.03 mum) and Au (0.05 mum) pads without using any flux. Fluxless and lead-free bonding technology in air ambient based on non eutectic 5 at. % Au-95 at. % Sn and eutectic 57 at. %Sn-43 at. % Bi with Au capping layer have been developed and studied. To understand the fluxless bonding principles in air ambient, phase formation mechanism of Au-Sn intermetallics embedded in Bi matrix has been postulated. The Au-Sn intermetallic-capping layer covers most outer surface of the samples and inhibits formation of oxide layer due to the minimizing exposure of (beta-Sn) phase to the air. In conclusion, new-lead free and fluxless bonding processes for flip chip packages were developed. In this work, Sn-rich Au-Sn flip chip solder bumps using vacuum deposition and electroplating process were successfully produced. It is

  11. Reliable and repeatable bonding technology for high temperature automotive power modules for electrified vehicles

    NASA Astrophysics Data System (ADS)

    Yoon, Sang Won; Glover, Michael D.; Mantooth, H. Alan; Shiozaki, Koji

    2013-01-01

    This paper presents the feasibility of highly reliable and repeatable copper-tin transient liquid phase (Cu-Sn TLP) bonding as applied to die attachment in high temperature operational power modules. Electrified vehicles are attracting particular interest as eco-friendly vehicles, but their power modules are challenged because of increasing power densities which lead to high temperatures. Such high temperature operation addresses the importance of advanced bonding technology that is highly reliable (for high temperature operation) and repeatable (for fabrication of advanced structures). Cu-Sn TLP bonding is employed herein because of its high remelting temperature and desirable thermal and electrical conductivities. The bonding starts with a stack of Cu-Sn-Cu metal layers that eventually transforms to Cu-Sn alloys. As the alloys have melting temperatures (Cu3Sn: > 600 °C, Cu6Sn5: > 400 °C) significantly higher than the process temperature, the process can be repeated without damaging previously bonded layers. A Cu-Sn TLP bonding process was developed using thin Sn metal sheets inserted between copper layers on silicon die and direct bonded copper substrates, emulating the process used to construct automotive power modules. Bond quality is characterized using (1) proof-of-concept fabrication, (2) material identification using scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis, and (3) optical analysis using optical microscopy and scanning acoustic microscope. The feasibility of multiple-sided Cu-Sn TLP bonding is demonstrated by the absence of bondline damage in multiple test samples fabricated with double- or four-sided bonding using the TLP bonding process.

  12. Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

    NASA Astrophysics Data System (ADS)

    Xu, Chang; Cheng, Longjiu; Yang, Jinlong

    2014-09-01

    It is well known that double-ring boron clusters have got the special double aromaticity with delocalized π orbitals in two directions (tangential and radial), which are potential ligands centered by a transition metal. In this article, the transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8) are theoretically investigated by density functional theory calculations. These endohedral compounds have also got double aromaticity in both tangential and radial directions. Interestingly, the tangential delocalized π orbitals of boron ligands following the Huckle's (4n + 2) rule do not interact with the central metal, while the radial π orbitals of boron ligands are bonded with the central mental to form spd-π endohedral bonding. The spd-π endohedral bonding follows the 18e-principle in Ni@B14 and Fe@B16. However, due to the flat shape of the compounds, 14e (Cr@B14) and 16e (Ni@B12) can also be electronically very stable where the energy levels of the spd-π orbitals delocalized in z-direction rise up. This intriguing bonding model makes sense in further study of the boron chemistry.

  13. 27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... distilled spirits plant and adjacent bonded wine cellar. 19.162 Section 19.162 Alcohol, Tobacco Products and... bond for distilled spirits plant and adjacent bonded wine cellar. (a) One bond satisfying two requirements. A proprietor who operates a bonded wine cellar that is adjacent to the proprietor's...

  14. Tests on Double Layer Metalization

    NASA Technical Reports Server (NTRS)

    Woo, D. S.

    1983-01-01

    28 page report describes experiments in fabrication of integrated circuits with double-layer metalization. Double-layer metalization requires much less silicon "real estate" and allows more flexibility in placement of circuit elements than does single-layer metalization.

  15. Measuring the Double Helix

    SciTech Connect

    Mathew-Fenn, R.S.; Das, R.; Harbury, P.A.B.

    2009-05-26

    DNA is thought to behave as a stiff elastic rod with respect to the ubiquitous mechanical deformations inherent to its biology. To test this model at short DNA lengths, we measured the mean and variance of end-to-end length for a series of DNA double helices in solution, using small-angle x-ray scattering interference between gold nanocrystal labels. In the absence of applied tension, DNA is at least one order of magnitude softer than measured by single-molecule stretching experiments. Further, the data rule out the conventional elastic rod model. The variance in end-to-end length follows a quadratic dependence on the number of base pairs rather than the expected linear dependence, indicating that DNA stretching is cooperative over more than two turns of the DNA double helix. Our observations support the idea of long-range allosteric communication through DNA structure.

  16. Double meningocele. Case report.

    PubMed

    Durmaz, R; Arslantaş, A; Ozön, Y H; Tel, E

    2000-01-01

    The coexistence of two distinct meningoceles of the spine is a very unusual event. We report a three-day-old boy with double meningoceles at the thoracic and lumbar levels. The connection between the stalk of the thoracic meningocele and the spinal cord, as seen on magnetic resonance imaging, showed a neurological involvement in this lesion. Our case is only the third without association of congenital anomalies or neurofibromatosis to be reported to date. PMID:11196754

  17. Homologous Pairing between Long DNA Double Helices

    NASA Astrophysics Data System (ADS)

    Mazur, Alexey K.

    2016-04-01

    Molecular recognition between two double stranded (ds) DNA with homologous sequences may not seem compatible with the B-DNA structure because the sequence information is hidden when it is used for joining the two strands. Nevertheless, it has to be invoked to account for various biological data. Using quantum chemistry, molecular mechanics, and hints from recent genetics experiments, I show here that direct recognition between homologous dsDNA is possible through the formation of short quadruplexes due to direct complementary hydrogen bonding of major-groove surfaces in parallel alignment. The constraints imposed by the predicted structures of the recognition units determine the mechanism of complexation between long dsDNA. This mechanism and concomitant predictions agree with the available experimental data and shed light upon the sequence effects and the possible involvement of topoisomerase II in the recognition.

  18. Homologous Pairing between Long DNA Double Helices.

    PubMed

    Mazur, Alexey K

    2016-04-15

    Molecular recognition between two double stranded (ds) DNA with homologous sequences may not seem compatible with the B-DNA structure because the sequence information is hidden when it is used for joining the two strands. Nevertheless, it has to be invoked to account for various biological data. Using quantum chemistry, molecular mechanics, and hints from recent genetics experiments, I show here that direct recognition between homologous dsDNA is possible through the formation of short quadruplexes due to direct complementary hydrogen bonding of major-groove surfaces in parallel alignment. The constraints imposed by the predicted structures of the recognition units determine the mechanism of complexation between long dsDNA. This mechanism and concomitant predictions agree with the available experimental data and shed light upon the sequence effects and the possible involvement of topoisomerase II in the recognition. PMID:27127987

  19. The double massa intermedia

    PubMed Central

    Baydin, Serhat; Gungor, Abuzer; Baran, Oguz; Tanriover, Necmettin; Rhoton, Albert L.

    2016-01-01

    Background: To describe the rare finding of a double massa intermedia (MI). Typically, the MI (interthalamic adhesion) is a single bridge of gray matter connecting the medial surfaces of the thalami. Methods: Twelve formalin- and alcohol-fixed human third ventricles were examined from superior to inferior by fiber dissection technique under ×6 to ×40 magnifications and with the endoscope. Results: In all hemispheres, the anterior and posterior commissure were defined. The MI, which bridges the medial surfaces of the thalami, was defined in all hemispheres. In one hemisphere, there was a second bridge between the thalami, located posteroinferior to the common MI. Endoscopic view confirmed that there was a second MI in this specimen. The MI usually traverses the third ventricle posterior to the foramen of Monro and connects the paired thalami. The MI is an important landmark during endoscopic and microscopic surgeries of the third ventricle. Although a double MI is very rare, surgeons should be aware of the possibility in their surgical planning. Conclusion: The surgeon should be aware of the possibility of a double MI to avoid confusion during third ventricle surgery. PMID:27127695

  20. Double face sealing device

    NASA Technical Reports Server (NTRS)

    Weddendorf, Bruce (Inventor)

    1991-01-01

    A double face sealing device is disclosed for mounting between two surfaces to provide an air-tight and fluid-tight seal between a closure member bearing one of the surfaces and a structure or housing bearing the other surface which extends around the opening or hatchway to be closed. The double face sealing device includes a plurality of sections or segments mounted to one of the surfaces, each having a main body portion, a pair of outwardly extending and diverging, cantilever, spring arms, and a pair of inwardly extending and diverging, cantilever, spring arms, an elastomeric cover on the distal, free ends of the outwardly extending and diverging spring arms, and an elastomeric cover on the distal, free, ends of the outwardly extending and diverging spring arms, and an elastomeric cover on the distal, free ends of the inwardly extending and diverging spring arms. The double face sealing device has application or use in all environments requiring a seal, but is particularly useful to seal openings or hatchways between compartments of spacecraft or aircraft.

  1. Trimeric and Tetrameric Electron-Deficient Porphyrin Tapes.

    PubMed

    Mori, Hirotaka; Kim, Taeyeon; Kim, Dongho; Osuka, Atsuhiro

    2016-05-01

    New hybrid porphyrin tapes comprising meso-3,5-di-tert-butylphenyl-substituted Zn(II) -porphyrins (D) and meso-pentafluorophenyl-substituted Zn(II) -porphyrins (A) were synthesized via cross-condensation of meso-formyl porphyrins 1, 5, and 9 with oligopyrromethanes 2 and 6 as key steps. These hybrid tapes exhibit improved solubilities and enhanced chemical stability as compared with original Dn porphyrin tapes, and all display remarkably coplanar structures favorable for π-conjugation. The absorption spectrum of ADDA displays Q-like bands at 1400 and 1657 nm with a vibronic structure characteristic of porphyrinoids. The cyclic voltammograms exhibited positively shifted oxidation and reduction waves in the order of DDD

  2. Viscoelastic analysis of bonded connections

    NASA Astrophysics Data System (ADS)

    Carpenter, William C.

    1991-05-01

    Analysis of bonded configurations is made difficult because of the thin adhesive layer and the stress singularities which exist at the edges of bonded configurations at the bimaterial interfaces. This paper is concerned with the use of lap joint theories with regard to viscoelastic analysis of adhesively bonded configurations. Viscoelastic analyses of adhesively bonded joints were performed using the Laplace transform technique. The inverse transforms were obtained numerically. The results have become the benchmark against which other numerical results are compared. In this analysis, control parameters are set to exactly duplicate the assumptions of the earlier work. The analysis is advanced with time using the Runge-Kutta integration formula in a direct integration procedure. The direct integration procedure has the advantage that it is computationally simple, has minimal storage requirements, and requires very little programming effort to transform an elastic analysis algorithm into a viscoelastic analysis algorithm. The results obtained with the finite element analysis algorithm described are effectively identical to those of the earlier work.

  3. Bonded polyimide fuel cell package

    DOEpatents

    Morse, Jeffrey D.; Jankowski, Alan; Graff, Robert T.; Bettencourt, Kerry

    2010-06-08

    Described herein are processes for fabricating microfluidic fuel cell systems with embedded components in which micron-scale features are formed by bonding layers of DuPont Kapton.TM. polyimide laminate. A microfluidic fuel cell system fabricated using this process is also described.

  4. Enhanced rigid-bond restraints

    SciTech Connect

    Thorn, Andrea; Dittrich, Birger; Sheldrick, George M.

    2012-07-01

    An extension is proposed to the rigid-bond description of atomic thermal motion in crystals. The rigid-bond model [Hirshfeld (1976 ▶). Acta Cryst. A32, 239–244] states that the mean-square displacements of two atoms are equal in the direction of the bond joining them. This criterion is widely used for verification (as intended by Hirshfeld) and also as a restraint in structure refinement as suggested by Rollett [Crystallographic Computing (1970 ▶), edited by F. R. Ahmed et al., pp. 167–181. Copenhagen: Munksgaard]. By reformulating this condition, so that the relative motion of the two atoms is required to be perpendicular to the bond, the number of restraints that can be applied per anisotropic atom is increased from about one to about three. Application of this condition to 1,3-distances in addition to the 1,2-distances means that on average just over six restraints can be applied to the six anisotropic displacement parameters of each atom. This concept is tested against very high resolution data of a small peptide and employed as a restraint for protein refinement at more modest resolution (e.g. 1.7 Å)

  5. Electronegativity and the Bond Triangle

    ERIC Educational Resources Information Center

    Meek, Terry L.; Garner, Leah D.

    2005-01-01

    The usefulness of the bond triangle for categorizing compounds of the main-group elements may be extended by the use of weighted average electronegativities to allow distinction between compounds of the same elements with different stoichiometries. In such cases a higher valency for the central atom leads to greater covalent character and the…

  6. Visualizing Bent Bonds in Cyclopropane

    ERIC Educational Resources Information Center

    Bertolini, Thomas M.

    2004-01-01

    A two-minute overhead demonstration using a molecular model kit is employed for illustrating the unique binding of cyclopropane. It is reported that most model kits, much like an sp (super 3) hybridized carbon atom, resist forming 60-degree bond angles.

  7. Non-bonded ultrasonic transducer

    DOEpatents

    Eoff, J.M.

    1984-07-06

    A mechanically assembled non-bonded ultrasonic transducer includes a substrate, a piezoelectric film, a wetting agent, a thin metal electrode, and a lens held in intimate contact by a mechanical clamp. No epoxy or glue is used in the assembly of this device.

  8. Bonding Elastomers To Metal Substrates

    NASA Technical Reports Server (NTRS)

    Dickerson, George E.; Kelley, Henry L.

    1990-01-01

    Improved, economical method for bonding elastomers to metals prevents failures caused by debonding. In new technique, vulcanization and curing occur simultaneously in specially designed mold that acts as form for desired shape of elastomer and as container that positions and supports metal parts. Increases interface adhesion between metal, adhesive, and elastomer.

  9. Mother-To-Infant 'Bonding'.

    ERIC Educational Resources Information Center

    Herbert, M.; And Others

    1982-01-01

    Critically reviews the concept of "bonding," exploring its empirical basis and the implications that follow from its application in practice. Among the conclusions reached are that there is a tendency to oversimplify attachment phenomena and that the notion of a sensitive period for attachment has no direct empirical support. (RH)

  10. Characterization of mode I and mixed-mode failure of adhesive bonds between composite adherends

    NASA Technical Reports Server (NTRS)

    Mall, S.; Johnson, W. S.

    1986-01-01

    A combined experimental and analytical investigation of an adhesively bonded composite joint was conducted to characterize both the static and fatigue beyond growth mechanism under mode 1 and mixed-mode 1 and 2 loadings. Two bonded systems were studied: graphite/epoxy adherends bonded with EC 3445 and FM-300 adhesives. For each bonded system, two specimen types were tested: a double-cantilever-beam specimen for mode 1 loading and a cracked-lapshear specimen for mixed-mode 1 and 2 loading. In all specimens tested, failure occurred in the form of debond growth. Debonding always occurred in a cohesive manner with EC 3445 adhesive. The FM-300 adhesive debonded in a cohesive manner under mixed-mode 1 and 2 loading, but in a cohesive, adhesive, or combined cohesive and adhesive manner under mode 1 loading. Total strain-energy release rate appeared to be the driving parameter for debond growth under static and fatigue loadings.

  11. Characterization of mode 1 and mixed-mode failure of adhesive bonds between composite adherends

    NASA Technical Reports Server (NTRS)

    Mall, S.; Johnson, W. S.

    1985-01-01

    A combined experimental and analytical investigation of an adhesively bonded composite joint was conducted to characterize both the static and fatigue beyond growth mechanism under mode 1 and mixed-mode 1 and 2 loadings. Two bonded systems were studied: graphite/epoxy adherends bonded with EC 3445 and FM-300 adhesives. For each bonded system, two specimen types were tested: a double-cantilever-beam specimen for mode 1 loading and a cracked-lapshear specimen for mixed-mode 1 and 2 loading. In all specimens tested, failure occurred in the form of debond growth. Debonding always occurred in a cohesive manner with EC 3445 adhesive. The FM-300 adhesive debonded in a cohesive manner under mixed-mode 1 and 2 loading, but in a cohesive, adhesive, or combined cohesive and adhesive manner under mode 1 loading. Total strain-energy release rate appeared to be the driving parameter for debond growth under static and fatigue loadings.

  12. Effect of non-bonded interactions on failure morphology of a defective graphene sheet

    NASA Astrophysics Data System (ADS)

    Degefe, Muse; Parashar, Avinash

    2016-04-01

    Molecular dynamics based atomistic modeling was performed to predict and quantify the effect of non-bonded interactions on the failure morphology of vacancy-affected sheets of graphene. A defective sheet of graphene containing vacancy defects was simulated in conjunction with the non-bonded interactions experienced due to the presence of a pristine sheet of graphene. In this study, the author revealed the mechanical properties and failure morphology of bilayer graphene sheets under the influence of single, double and multi-vacancy defects. It was concluded on the basis of atomistic simulations that non-bonded interactions as well as the stiffness of the pristine graphene sheet has significant impact on the failure morphology of the accompanied defective sheet of graphene. Non-bonded interactions in conjunction with defects can be further explored for modifying the brittle nature of graphene to ductile.

  13. Ribosomal crystallography: peptide bond formation and its inhibition.

    PubMed

    Bashan, Anat; Zarivach, Raz; Schluenzen, Frank; Agmon, Ilana; Harms, Joerg; Auerbach, Tamar; Baram, David; Berisio, Rita; Bartels, Heike; Hansen, Harly A S; Fucini, Paola; Wilson, Daniel; Peretz, Moshe; Kessler, Maggie; Yonath, Ada

    2003-09-01

    Ribosomes, the universal cellular organelles catalyzing the translation of genetic code into proteins, are protein/RNA assemblies, of a molecular weight 2.5 mega Daltons or higher. They are built of two subunits that associate for performing protein biosynthesis. The large subunit creates the peptide bond and provides the path for emerging proteins. The small has key roles in initiating the process and controlling its fidelity. Crystallographic studies on complexes of the small and the large eubacterial ribosomal subunits with substrate analogs, antibiotics, and inhibitors confirmed that the ribosomal RNA governs most of its activities, and indicated that the main catalytic contribution of the ribosome is the precise positioning and alignment of its substrates, the tRNA molecules. A symmetry-related region of a significant size, containing about two hundred nucleotides, was revealed in all known structures of the large ribosomal subunit, despite the asymmetric nature of the ribosome. The symmetry rotation axis, identified in the middle of the peptide-bond formation site, coincides with the bond connecting the tRNA double-helical features with its single-stranded 3' end, which is the moiety carrying the amino acids. This thus implies sovereign movements of tRNA features and suggests that tRNA translocation involves a rotatory motion within the ribosomal active site. This motion is guided and anchored by ribosomal nucleotides belonging to the active site walls, and results in geometry suitable for peptide-bond formation with no significant rearrangements. The sole geometrical requirement for this proposed mechanism is that the initial P-site tRNA adopts the flipped orientation. The rotatory motion is the major component of unified machinery for peptide-bond formation, translocation, and nascent protein progression, since its spiral nature ensures the entrance of the nascent peptide into the ribosomal exit tunnel. This tunnel, assumed to be a passive path for the

  14. Nondestructive Determination of Bond Strength

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Although many nondestructive techniques have been applied to detect disbonds in adhesive joints, no absolutely reliable nondestructive method has been developed to detect poor adhesion and evaluate the strength of bonded joints prior to the present work which used nonlinear ultrasonic methods to investigate adhesive bond cure conditions. Previously, a variety of linear and nonlinear ultrasonic methods with water coupling had been used to study aluminum-adhesive-aluminum laminates, prepared under different adhesive curing conditions, for possible bond strength determination. Therefore, in the course of this research effort, a variety of finite-amplitude experimental methods which could possibly differentiate various cure conditions were investigated, including normal and oblique incidence approaches based on nonlinear harmonic generation as well as several non-collinear two-wave interaction approaches. Test samples were mechanically scanned in various ways with respect to the focus of a transmitting transducer operated at several variable excitation frequencies and excitation levels. Even when powerful sample-related resonances were exploited by means of a frequency scanning approach, it was very difficult to isolate the nonlinear characteristics of adhesive bonds. However, a multi-frequency multi-power approach was quite successful and reliable. Ultrasonic tone burst signals at increasing power levels, over a wide frequency range, were transmitted through each bond specimen to determine its excitation dependent nonlinear harmonic resonance behavior. Relative amplitude changes were observed particularly in the higher harmonic spectral data and analyzed using a local displacement and strain analysis in the linear approximation. Two analysis approaches of the excitation-dependent data at specific resonances were found to be quite promising. One of these approaches may represent a very robust algorithm for classifying an adhesive bond as being properly cured or not

  15. An Investigation of the Interrelationships Between Linear and NonLinear Polarizabilities and Bond Length Alternation on Connugated Organic Molecules

    NASA Technical Reports Server (NTRS)

    Gorman, C. B.; Marder, S. R.

    1993-01-01

    A computational method was devised to explore the relationship between charge separation, geometry, molecular dipole moment, polarizability, and hyperpolarizabilities in comjugated organic molecules. It is shown that bond length alternation (the average difference in length between single and double bonds in the molecule) is a key structurally observable parameter that can be correlated with hyperpolarizabilities and is thus relevant to the optimizaton of molecules and materials.

  16. Asymmetric Synthesis of Overcrowded Alkenes by Transfer of Axial Single Bond Chirality to Axial Double Bond Chirality.

    PubMed

    Geertsema; Meetsma; Feringa

    1999-09-01

    Optically active overcrowded alkenes were synthesized by employing bis-beta-naphthol as a chiral template during an intramolecular coupling reaction. The major isomer 2 has a unique helical structure with twisted and folded structural moieties. Removal of the chiral template afforded overcrowded thioxanthylidene 3 with 96 % ee, which indicates that no racemization or isomerization of the enantiomers took place. PMID:10508366

  17. (11)C[double bond, length as m-dash]O bonds made easily for positron emission tomography radiopharmaceuticals.

    PubMed

    Rotstein, Benjamin H; Liang, Steven H; Placzek, Michael S; Hooker, Jacob M; Gee, Antony D; Dollé, Frédéric; Wilson, Alan A; Vasdev, Neil

    2016-08-22

    The positron-emitting radionuclide carbon-11 ((11)C, t1/2 = 20.3 min) possesses the unique potential for radiolabeling of any biological, naturally occurring, or synthetic organic molecule for in vivo positron emission tomography (PET) imaging. Carbon-11 is most often incorporated into small molecules by methylation of alcohol, thiol, amine or carboxylic acid precursors using [(11)C]methyl iodide or [(11)C]methyl triflate (generated from [(11)C]carbon dioxide or [(11)C]methane). Consequently, small molecules that lack an easily substituted (11)C-methyl group are often considered to have non-obvious strategies for radiolabeling and require a more customized approach. [(11)C]Carbon dioxide itself, [(11)C]carbon monoxide, [(11)C]cyanide, and [(11)C]phosgene represent alternative reactants to enable (11)C-carbonylation. Methodologies developed for preparation of (11)C-carbonyl groups have had a tremendous impact on the development of novel PET tracers and provided key tools for clinical research. (11)C-Carbonyl radiopharmaceuticals based on labeled carboxylic acids, amides, carbamates and ureas now account for a substantial number of important imaging agents that have seen translation to higher species and clinical research of previously inaccessible targets, which is a testament to the creativity, utility and practicality of the underlying radiochemistry. PMID:27276357

  18. Adhesive wafer bonding for MEMS applications

    NASA Astrophysics Data System (ADS)

    Dragoi, Viorel; Glinsner, Thomas; Mittendorfer, Gerald; Wieder, Bernhard; Lindner, Paul

    2003-04-01

    Low temperature wafer bonding is a powerful technique for MEMS/MOEMS devices fabrication and packaging. Among the low temperature processes adhesive bonding focuses a high technological interest. Adhesive wafer bonding is a bonding approach using an intermediate layer for bonding (e.g. glass, polymers, resists, polyimides). The main advantages of this method are: surface planarization, encapsulation of structures on the wafer surface, particle compensation and decrease of annealing temperature after bonding. This paper presents results on adhesive bonding using spin-on glass and Benzocyclobutene (BCB) from Dow Chemicals. The advantages of using adhesive bonding for MEMS applications will be illustrated be presenting a technology of fabricating GaAs-on-Si substrates (up to 150 mm diameter) and results on BCB bonding of Si wafers (200 mm diameter).

  19. Colloidal Double Quantum Dots

    PubMed Central

    2016-01-01

    Conspectus Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole–dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single

  20. Colloidal Double Quantum Dots.

    PubMed

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon

  1. Describing the chemical bonding in C70 and C70O3 - A quantum chemical topology study

    NASA Astrophysics Data System (ADS)

    Bil, Andrzej; Latajka, Zdzisław; Hutter, Jürg; Morrison, Carole A.

    2014-03-01

    Cc-Cc and Ca-Cb bonds in C70 have dominant characteristics of double bonds, whereas the remaining six other types of bonds are single bonds with contributions from π-electron density. 'Single' bonds can act as active sites in chemical reactions which would typically require a multiple bond, such as addition of an ozone molecule, due to the fact that all adjacent bonds can serve as an efficient source of π-electron density. Thus any alteration in the electron density distribution following functionalization has far-reaching impact. We note that formation of the most stable ozonide isomer causes the smallest total perturbation in the electron density of the parent fullerene and C-C bond evolution correlates well with the shape of the minimum energy path for the ozone ring opening reaction on the fullerene surface. Finally, we observe that the O-O bond in C70O3 is protocovalent, and as such resembles the O-O bond in H2O2.

  2. On the nature of chemical bonding in the all-metal aromatic [Sb3Au3Sb3](3-) sandwich complex.

    PubMed

    You, Xue-Rui; Tian, Wen-Juan; Li, Da-Zhi; Wang, Ying-Jin; Li, Rui; Feng, Lin-Yan; Zhai, Hua-Jin

    2016-05-21

    In a recent communication, an all-metal aromatic sandwich [Sb3Au3Sb3](3-) was synthesized and characterized. We report herein a density-functional theory (DFT) study on the chemical bonding of this unique cluster, which makes use of a number of computational tools, including the canonical molecular orbital (CMO), adaptive natural density partitioning (AdNDP), Wiberg bond index, and orbital composition analyses. The 24-electron, triangular prismatic sandwich is intrinsically electron-deficient, being held together via six Sb-Sb, three Au-Au, and six Sb-Au links. A standard, qualitative bonding analysis suggests that all CMOs are primarily located on the three Sb3/Au3/Sb3 layers, three Au 6s based CMOs are fully occupied, and the three extra charges are equally shared by the two cyclo-Sb3 ligands. This bonding picture is referred to as the zeroth order model, in which the cluster can be formally formulated as [Sb3(1.5+)Au3(3-)Sb3(1.5+)](3-) or [Sb3(0)Au3(3-)Sb3(0)]. However, the system is far more complex and covalent than the above picture. Seventeen CMOs out of 33 in total involve remarkable Sb → Au electron donation and Sb ← Au back-donation, which are characteristic of covalent bonding and effectively redistribute electrons from the Sb3 and Au3 layers to the interlayer edges. This effect collectively leads to three Sb-Au-Sb three-center two-electron (3c-2e) σ bonds as revealed in the AdNDP analyses, despite the fact that not a single such bond can be identified from the CMOs. Orbital composition analyses for the 17 CMOs allow a quantitative understanding of how electron donation and back-donation redistribute the charges within the system from the formal Sb3(0)/Au3(3-) charge states in the zeroth order model to the effective Sb3(1.5-)/Au3(0) charge states, the latter being revealed from the natural bond orbital analysis. PMID:27124821

  3. Halogen bonds in biological molecules

    PubMed Central

    Auffinger, Pascal; Hays, Franklin A.; Westhof, Eric; Ho, P. Shing

    2004-01-01

    Short oxygen–halogen interactions have been known in organic chemistry since the 1950s and recently have been exploited in the design of supramolecular assemblies. The present survey of protein and nucleic acid structures reveals similar halogen bonds as potentially stabilizing inter- and intramolecular interactions that can affect ligand binding and molecular folding. A halogen bond in biomolecules can be defined as a short CX···OY interaction (CX is a carbon-bonded chlorine, bromine, or iodine, and OY is a carbonyl, hydroxyl, charged carboxylate, or phosphate group), where the X···O distance is less than or equal to the sums of the respective van der Waals radii (3.27 Å for Cl···O, 3.37Å for Br···O, and 3.50 Å for I···O) and can conform to the geometry seen in small molecules, with the CX···O angle ≈165° (consistent with a strong directional polarization of the halogen) and the X···OY angle ≈120°. Alternative geometries can be imposed by the more complex environment found in biomolecules, depending on which of the two types of donor systems are involved in the interaction: (i) the lone pair electrons of oxygen (and, to a lesser extent, nitrogen and sulfur) atoms or (ii) the delocalized π -electrons of peptide bonds or carboxylate or amide groups. Thus, the specific geometry and diversity of the interacting partners of halogen bonds offer new and versatile tools for the design of ligands as drugs and materials in nanotechnology. PMID:15557000

  4. Halogen bonds in biological molecules.

    PubMed

    Auffinger, Pascal; Hays, Franklin A; Westhof, Eric; Ho, P Shing

    2004-11-30

    Short oxygen-halogen interactions have been known in organic chemistry since the 1950s and recently have been exploited in the design of supramolecular assemblies. The present survey of protein and nucleic acid structures reveals similar halogen bonds as potentially stabilizing inter- and intramolecular interactions that can affect ligand binding and molecular folding. A halogen bond in biomolecules can be defined as a short C-X...O-Y interaction (C-X is a carbon-bonded chlorine, bromine, or iodine, and O-Y is a carbonyl, hydroxyl, charged carboxylate, or phosphate group), where the X...O distance is less than or equal to the sums of the respective van der Waals radii (3.27 A for Cl...O, 3.37 A for Br...O, and 3.50 A for I...O) and can conform to the geometry seen in small molecules, with the C-X...O angle approximately 165 degrees (consistent with a strong directional polarization of the halogen) and the X...O-Y angle approximately 120 degrees . Alternative geometries can be imposed by the more complex environment found in biomolecules, depending on which of the two types of donor systems are involved in the interaction: (i) the lone pair electrons of oxygen (and, to a lesser extent, nitrogen and sulfur) atoms or (ii) the delocalized pi -electrons of peptide bonds or carboxylate or amide groups. Thus, the specific geometry and diversity of the interacting partners of halogen bonds offer new and versatile tools for the design of ligands as drugs and materials in nanotechnology. PMID:15557000

  5. Configuring bonds between first-row transition metals.

    PubMed

    Eisenhart, Reed J; Clouston, Laura J; Lu, Connie C

    2015-11-17

    Alfred Werner, who pioneered the field of coordination chemistry, envisioned coordination complexes as a single, transition metal atom at the epicenter of a vast ligand space. The idea that the locus of a coordination complex could be shared by multiple metals held together with covalent bonds would eventually lead to the discovery of the quadruple and quintuple bond, which have no analogues outside of the transition metal block. Metal-metal bonding can be classified into homometallic and heterometallic groups. Although the former is dominant, the latter is arguably more intriguing because of the inherently larger chemical space in which metal-metal bonding can be explored. In 2013, Lu and Thomas independently reported the isolation of heterometallic multiple bonds with exclusively first-row transition metals. Structural and theoretical data supported triply bonded Fe-Cr and Fe-V cores. This Account describes our continued efforts to configure bonds between first-row transition metals from titanium to copper. Double-decker ligands, or binucleating platforms that brace two transition metals in proximity, have enabled the modular synthesis of diverse metal-metal complexes. The resulting complexes are also ideal for investigating the effects of an "ancillary" metal on the properties and reactivities of an "active" metal center. A total of 38 bimetallic complexes have been compiled comprising 18 unique metal-metal pairings. Twenty-one of these bimetallics are strictly isostructural, allowing for a systematic comparison of metal-metal bonding. The nature of the chemical bond between first-row metals is remarkably variable and depends on two primary factors: the total d-electron count, and the metals' relative d-orbital energies. Showcasing the range of covalent bonding are a quintuply bonded (d-d)(10) Mn-Cr heterobimetallic and the singly bonded late-late pairings, e.g., Fe-Co, which adopt unusually high spin states. A long-term goal is to rationally tailor the

  6. Power module packaging with double sided planar interconnection and heat exchangers

    DOEpatents

    Liang, Zhenxian; Marlino, Laura D.; Ning, Puqi; Wang, Fei

    2015-05-26

    A double sided cooled power module package having a single phase leg topology includes two IGBT and two diode semiconductor dies. Each IGBT die is spaced apart from a diode semiconductor die, forming a switch unit. Two switch units are placed in a planar face-up and face-down configuration. A pair of DBC or other insulated metallic substrates is affixed to each side of the planar phase leg semiconductor dies to form a sandwich structure. Attachment layers are disposed on outer surfaces of the substrates and two heat exchangers are affixed to the substrates by rigid bond layers. The heat exchangers, made of copper or aluminum, have passages for carrying coolant. The power package is manufactured in a two-step assembly and heating process where direct bonds are formed for all bond layers by soldering, sintering, solid diffusion bonding or transient liquid diffusion bonding, with a specially designed jig and fixture.

  7. Adhesive-bonded scarf and stepped-lap joints

    NASA Technical Reports Server (NTRS)

    Hart-Smith, L. J.

    1973-01-01

    Continuum mechanics solutions are derived for the static load-carrying capacity of scarf and stepped-lap adhesive-bonded joints. The analyses account for adhesive plasticity and adherend stiffness imbalance and thermal mismatch. The scarf joint solutions include a simple algebraic formula which serves as a close lower bound, within a small fraction of a per cent of the true answer for most practical geometries and materials. Digital computer programs were developed and, for the stepped-lap joints, the critical adherend and adhesive stresses are computed for each step. The scarf joint solutions exhibit grossly different behavior from that for double-lap joints for long overlaps inasmuch as that the potential bond shear strength continues to increase with indefinitely long overlaps on the scarf joints. The stepped-lap joint solutions exhibit some characteristics of both the scarf and double-lap joints. The stepped-lap computer program handles arbitrary (different) step lengths and thickness and the solutions obtained have clarified potentially weak design details and the remedies. The program has been used effectively to optimize the joint proportions.

  8. Chemical Bonding Technology: Direct Investigation of Interfacial Bonds

    NASA Technical Reports Server (NTRS)

    Koenig, J. L.; Boerio, F. J.; Plueddemann, E. P.; Miller, J.; Willis, P. B.; Cuddihy, E. F.

    1986-01-01

    This is the third Flat-Plate Solar Array (FSA) Project document reporting on chemical bonding technology for terrestrial photovoltaic (PV) modules. The impetus for this work originated in the late 1970s when PV modules employing silicone encapsulation materials were undergoing delamination during outdoor exposure. At that time, manufacturers were not employing adhesion promoters and, hence, module interfaces in common with the silicone materials were only in physical contact and therefore easily prone to separation if, for example, water were to penetrate to the interfaces. Delamination with silicone materials virtually vanished when adhesion promoters, recommended by silicone manufacturers, were used. The activities related to the direct investigation of chemically bonded interfaces are described.

  9. Reactivity in the periphery of functionalised multiple bonds of heavier group 14 elements.

    PubMed

    Präsang, Carsten; Scheschkewitz, David

    2016-02-21

    Heavier group 14 multiple bonds have intrigued chemists since more than a century. The synthesis of stable compounds with double and triple bonds with silicon, germanium, tin and lead had considerable impact on modern ideas of chemical bonding. These developments were made possible by the use of bulky substituents that provide kinetic and thermodynamic protection. Since about a decade the compatibility of heavier multiple bonds with various functional groups has moved into focus. This review covers multiply bonded group 14 species with at least one additional reactive site. The vinylic functionalities of groups 1 and 17, resulting in nucleophilic and electrophilic disila vinyl groups, respectively, are the most prevalent and well-studied. They have been employed repeatedly for the transfer of heavier multiple bonds to yield low-valent group 14 compounds with novel structural motifs. Vinylic functionalities of groups 2 to 16 and a few σ-bonded transition metal complexes are experimentally known, but their reactivity has been studied to a lesser extent. Donor-coordinated multiple bonds are a relatively new field of research, but the large degree of unsaturation as isomers of alkynes (as well as residual functionality in some cases) offers considerable possibility for further manipulation, e.g. for the incorporation into more extended systems. Heavier allyl halides constitute the major part of heavier multiple bonds with a functional group in allylic position and some examples of successful transformations are given. At present, remote functionalities are basically limited to para-phenylene functionalised disilenes. The reported use of the latter for further derivatisation might encourage investigations in this direction. In summary, the study of peripherally functionalised multiple bonds with heavier group 14 elements is already well beyond its infancy and may be an instrumental factor in awakening the potential of group 14 chemistry for applications in polymers and

  10. Catch bond interaction between cell-surface sulfatase Sulf1 and glycosaminoglycans.

    PubMed

    Harder, Alexander; Möller, Ann-Kristin; Milz, Fabian; Neuhaus, Phillipp; Walhorn, Volker; Dierks, Thomas; Anselmetti, Dario

    2015-04-01

    In biological adhesion, the biophysical mechanism of specific biomolecular interaction can be divided in slip and catch bonds, respectively. Conceptually, slip bonds exhibit a reduced bond lifetime under increased external force and catch bonds, in contrast, exhibit an increased lifetime (for a certain force interval). Since 2003, a handful of biological systems have been identified to display catch bond properties. Upon investigating the specific interaction between the unique hydrophilic domain (HD) of the human cell-surface sulfatase Sulf1 against its physiological glycosaminoglycan (GAG) target heparan sulfate (HS) by single molecule force spectroscopy (SMFS), we found clear evidence of catch bond behavior in this system. The HD, ∼320 amino acids long with dominant positive charge, and its interaction with sulfated GAG-polymers were quantitatively investigated using atomic force microscopy (AFM) based force clamp spectroscopy (FCS) and dynamic force spectroscopy (DFS). In FCS experiments, we found that the catch bond character of HD against GAGs could be attributed to the GAG 6-O-sulfation site whereas only slip bond interaction can be observed in a GAG system where this site is explicitly lacking. We interpreted the binding data within the theoretical framework of a two state two path model, where two slip bonds are coupled forming a double-well interaction potential with an energy difference of ΔE ≈ 9 kBT and a compliance length of Δx ≈ 3.2 nm. Additional DFS experiments support this assumption and allow identification of these two coupled slip-bond states that behave consistently within the Kramers-Bell-Evans model of force-mediated dissociation. PMID:25863062

  11. Complexes between hypohalous acids and phosphine derivatives. Pnicogen bond versus halogen bond versus hydrogen bond

    NASA Astrophysics Data System (ADS)

    Li, Qingzhong; Zhu, Hongjie; Zhuo, Hongying; Yang, Xin; Li, Wenzuo; Cheng, Jianbo

    2014-11-01

    The complexes of HOBr:PH2Y (Y = H, F, Cl, Br, CH3, NH2, OH, and NO2), HOCl:PH2F, and HOI:PH2F have been investigated with ab initio calculations at the MP2/aug-cc-pVTZ level. Four types of structures (1, 2, 3a, and 3b) were observed for these complexes. 1 is stabilized by an O⋯P pnicogen bond, 2 by a P⋯X halogen bond, 3a by a H⋯P hydrogen bond and a P⋯X pnicogen bond, and 3b by H⋯P and H⋯Br hydrogen bonds. Their relative stability is related to the halogen X of HOX and the substituent Y of PH2Y. These structures can compete with interaction energy of -10.22 ∼ -29.40 kJ/mol. The Hsbnd O stretch vibration shows a small red shift in 1, a small irregular shift in 2, but a prominent red shift in 3a and 3b. The Xsbnd O stretch vibration exhibits a smaller red shift in 1, a larger red shift in 2, but an insignificant blue shift in 3a and 3b. The Psbnd Y stretch vibration displays a red shift in 1 but a blue shift in 2, 3a, and 3b. The formation mechanism, stability, and properties of these structures have been analyzed with molecular electrostatic potentials, orbital interactions, and non-covalent interaction index.

  12. Double pituitary adenomas.

    PubMed

    Iacovazzo, D; Bianchi, A; Lugli, F; Milardi, D; Giampietro, A; Lucci-Cordisco, E; Doglietto, F; Lauriola, L; De Marinis, L

    2013-04-01

    Double pituitary adenomas represent up to 2.6 % of pituitary adenomas in large surgical series and up to 3.3 % of patients with Cushing's disease have been found to have double or multiple pituitary adenomas. We report the case of a 60-year-old male patient whose medical history began in 2002 with erectile dysfunction; hyperprolactinemia was found and MRI showed a 6-mm area of delayed enhancement in the lateral portion of the right pituitary lobe. Treatment with cabergoline was started with normalization of prolactin levels; the following MRI, performed in 2005 and 2008, showed shrinkage of the pituitary lesion. In 2005, the patient began to manifest weight gain, hypertension, and facial plethora, but no further evaluations were done. In January 2010, the patient came to our attention and underwent multiple tests that suggested Cushing's disease. A new MRI was negative. Bilateral inferior petrosal sinus sampling showed significant pituitary-to-peripheral ratio and, in May 2010, the patient underwent exploratory pituitary surgery with evidence of a 1-2-mm white-coloured midline area compatible with pituitary adenoma that was surgically removed. Post-operatively, the patient's clinical conditions improved with onset of secondary hypoadrenalism. The histologic examination confirmed a pituitary adenoma (immunostaining was found to be positive for ACTH and negative for prolactin). We report the case of an ACTH-producing microadenoma metachronous to a prolactin secreting microadenoma although not confirmed histologically, shrunk by medical treatment. A review of data in the literature regarding double or multiple pituitary adenomas has also been done. PMID:23325364

  13. The Double Star mission

    NASA Astrophysics Data System (ADS)

    Liu, Z. X.; Escoubet, C. P.; Pu, Z.; Laakso, H.; Shi, J. K.; Shen, C.; Hapgood, M.

    2005-11-01

    The Double Star Programme (DSP) was first proposed by China in March, 1997 at the Fragrant Hill Workshop on Space Science, Beijing, organized by the Chinese Academy of Science. It is the first mission in collaboration between China and ESA. The mission is made of two spacecraft to investigate the magnetospheric global processes and their response to the interplanetary disturbances in conjunction with the Cluster mission. The first spacecraft, TC-1 (Tan Ce means "Explorer"), was launched on 29 December 2003, and the second one, TC-2, on 25 July 2004 on board two Chinese Long March 2C rockets. TC-1 was injected in an equatorial orbit of 570x79000 km altitude with a 28° inclination and TC-2 in a polar orbit of 560x38000 km altitude. The orbits have been designed to complement the Cluster mission by maximizing the time when both Cluster and Double Star are in the same scientific regions. The two missions allow simultaneous observations of the Earth magnetosphere from six points in space. To facilitate the comparison of data, half of the Double Star payload is made of spare or duplicates of the Cluster instruments; the other half is made of Chinese instruments. The science operations are coordinated by the Chinese DSP Scientific Operations Centre (DSOC) in Beijing and the European Payload Operations Service (EPOS) at RAL, UK. The spacecraft and ground segment operations are performed by the DSP Operations and Management Centre (DOMC) and DSOC in China, using three ground station, in Beijing, Shanghai and Villafranca.

  14. Study of bump bonding technology

    SciTech Connect

    Selcuk Cihangir et al.

    2003-10-17

    Pixel detectors proposed for the new generation of hadron collider experiments will use bump-bonding technology based on either indium or Pb/Sn solder to connect the front-end readout chips to the silicon pixel sensors. We have previously reported large-scale tests of the yield using both indium and Pb/Sn solder bump [1]. The conclusion is that both seem to be viable for pixel detectors. We have also carried out studies of various effects (e.g. storage over long period, effect of heating and cooling, and radiation) on both types of bump bonds using daisy-chained parts on a small scale [2], [3]. Overall, these tests showed little changes in the integrity of the bump connections. Nevertheless, questions still remain on the long-term reliability of the bumps due to thermal cycle effects, attachment to a substrate with a different coefficient of thermal expansion (CTE), and radiation.

  15. Opioids and social bonding: naltrexone reduces feelings of social connection.

    PubMed

    Inagaki, Tristen K; Ray, Lara A; Irwin, Michael R; Way, Baldwin M; Eisenberger, Naomi I

    2016-05-01

    Close social bonds are critical to a happy and fulfilled life and yet little is known, in humans, about the neurochemical mechanisms that keep individuals feeling close and connected to one another. According to the brain opioid theory of social attachment, opioids may underlie the contented feelings associated with social connection and may be critical to continued bonding. However, the role of opioids in feelings of connection toward close others has only begun to be examined in humans. In a double-blind, placebo-controlled, crossover study of naltrexone (an opioid antagonist), 31 volunteers took naltrexone for 4 days and placebo for 4 days (separated by a 10-day washout period). Participants came to the laboratory once on the last day of taking each drug to complete a task designed to elicit feelings of social connection. Participants also completed daily reports of feelings of social connection while on naltrexone and placebo. In line with hypotheses, and for the first time in humans, results demonstrated that naltrexone (vs placebo) reduced feelings of connection both in the laboratory and in daily reports. These results highlight the importance of opioids for social bonding with close others, lending support to the brain opioid theory of social attachment. PMID:26796966

  16. An investigation of the interrelationships between linear and nonlinear polarizabilities and bond-length alternation in conjugated organic molecules.

    PubMed Central

    Gorman, C B; Marder, S R

    1993-01-01

    A computational method was devised to explore the relationship of charge separation, geometry, molecular dipole moment (mu), polarizability (alpha), and hyperpolariz-abilities (beta, gamma) in conjugated organic molecules. We show that bond-length alternation (the average difference in length between single and double bonds in the molecule) is a key structurally observable parameter that can be correlated with hyperpolarizabilities and is thus relevant to the optimization of molecules and materials. By using this method, the relationship of bond-length alternation, mu, alpha, beta, and gamma for linear conjugated molecules is illustrated, and those molecules with maximized alpha, beta, and gamma are described. PMID:11607441

  17. Catalytic diamination of olefins via N-N bond activation.

    PubMed

    Zhu, Yingguang; Cornwall, Richard G; Du, Haifeng; Zhao, Baoguo; Shi, Yian

    2014-12-16

    CONSPECTUS: Vicinal diamines are important structural motifs present in various biologically and chemically significant molecules. Direct diamination of olefins provides an effective approach to this class of compounds. Unlike well-established oxidation processes such as epoxidation, dihydroxylation, and aminohydroxylation, direct diamination of olefins had remained a long-standing challenge and had been less well developed. In this Account, we summarize our recent studies on Pd(0)- and Cu(I)-catalyzed diaminations of olefins using di-tert-butyldiaziridinone and its related analogues as nitrogen sources via N-N bond activation. A wide variety of imidazolidinones, cyclic sulfamides, indolines, imidazolinones, and cyclic guanidines can be obtained from conjugated dienes and terminal olefins. For conjugated dienes, the diamination proceeds regioselectively at the internal double bond with the Pd(0) catalyst. Mechanistic studies show that the diamination likely involves a four-membered Pd(II) species resulting from the insertion of Pd(0) into the N-N bond of di-tert-butyldiaziridinone. Interestingly, the Cu(I)-catalyzed process occurs regioselectively at either the terminal or internal double bond depending on the reaction conditions via two mechanistically distinct pathways. The Cu(I) catalyst cleaves the N-N bond of di-tert-butyldiaziridinone to form a Cu(II) nitrogen radical and a four-membered Cu(III) species, which are likely in rapid equilibrium. The Cu(II) nitrogen radical and the four-membered Cu(III) species lead to the terminal and internal diamination, respectively. Terminal olefins are effectively C-H diaminated at the allylic and homoallylic carbons with Pd(0) as catalyst and di-tert-butyldiaziridinone as nitrogen source, likely involving a diene intermediate generated in situ from the terminal olefin via formation of a π-allyl Pd complex and subsequent β-hydride elimination. When di-tert-butylthiadiaziridine 1,1-dioxide is used as nitrogen source

  18. Catalytic Diamination of Olefins via N–N Bond Activation

    PubMed Central

    2015-01-01

    Conspectus Vicinal diamines are important structural motifs present in various biologically and chemically significant molecules. Direct diamination of olefins provides an effective approach to this class of compounds. Unlike well-established oxidation processes such as epoxidation, dihydroxylation, and aminohydroxylation, direct diamination of olefins had remained a long-standing challenge and had been less well developed. In this Account, we summarize our recent studies on Pd(0)- and Cu(I)-catalyzed diaminations of olefins using di-tert-butyldiaziridinone and its related analogues as nitrogen sources via N–N bond activation. A wide variety of imidazolidinones, cyclic sulfamides, indolines, imidazolinones, and cyclic guanidines can be obtained from conjugated dienes and terminal olefins. For conjugated dienes, the diamination proceeds regioselectively at the internal double bond with the Pd(0) catalyst. Mechanistic studies show that the diamination likely involves a four-membered Pd(II) species resulting from the insertion of Pd(0) into the N–N bond of di-tert-butyldiaziridinone. Interestingly, the Cu(I)-catalyzed process occurs regioselectively at either the terminal or internal double bond depending on the reaction conditions via two mechanistically distinct pathways. The Cu(I) catalyst cleaves the N–N bond of di-tert-butyldiaziridinone to form a Cu(II) nitrogen radical and a four-membered Cu(III) species, which are likely in rapid equilibrium. The Cu(II) nitrogen radical and the four-membered Cu(III) species lead to the terminal and internal diamination, respectively. Terminal olefins are effectively C–H diaminated at the allylic and homoallylic carbons with Pd(0) as catalyst and di-tert-butyldiaziridinone as nitrogen source, likely involving a diene intermediate generated in situ from the terminal olefin via formation of a π-allyl Pd complex and subsequent β-hydride elimination. When di-tert-butylthiadiaziridine 1,1-dioxide is used as nitrogen source

  19. Quality control of microelectronic wire bonds

    NASA Technical Reports Server (NTRS)

    Thiel, R. A.; Schmidt, G. D.

    1975-01-01

    Report evaluates ultrasonic bonding of small-diameter aluminum wire joined to ceramic substrates metalized with thin-film and thick-film gold. Quick testing technique for nondestructive location of poor wire bonds is also presented.

  20. 7 CFR 1788.12 - Contractors' bonds.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AGRICULTURE (CONTINUED) RUS FIDELITY AND INSURANCE REQUIREMENTS FOR ELECTRIC AND TELECOMMUNICATIONS BORROWERS Insurance for Contractors, Engineers, and Architects, Electric Borrowers § 1788.12 Contractors' bonds. Electric borrowers shall require contractors to obtain contractors' bonds when required by part...

  1. 7 CFR 1788.12 - Contractors' bonds.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AGRICULTURE (CONTINUED) RUS FIDELITY AND INSURANCE REQUIREMENTS FOR ELECTRIC AND TELECOMMUNICATIONS BORROWERS Insurance for Contractors, Engineers, and Architects, Electric Borrowers § 1788.12 Contractors' bonds. Electric borrowers shall require contractors to obtain contractors' bonds when required by part...

  2. 7 CFR 1788.12 - Contractors' bonds.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AGRICULTURE (CONTINUED) RUS FIDELITY AND INSURANCE REQUIREMENTS FOR ELECTRIC AND TELECOMMUNICATIONS BORROWERS Insurance for Contractors, Engineers, and Architects, Electric Borrowers § 1788.12 Contractors' bonds. Electric borrowers shall require contractors to obtain contractors' bonds when required by part...

  3. 7 CFR 1788.12 - Contractors' bonds.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AGRICULTURE (CONTINUED) RUS FIDELITY AND INSURANCE REQUIREMENTS FOR ELECTRIC AND TELECOMMUNICATIONS BORROWERS Insurance for Contractors, Engineers, and Architects, Electric Borrowers § 1788.12 Contractors' bonds. Electric borrowers shall require contractors to obtain contractors' bonds when required by part...

  4. 7 CFR 1788.12 - Contractors' bonds.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AGRICULTURE (CONTINUED) RUS FIDELITY AND INSURANCE REQUIREMENTS FOR ELECTRIC AND TELECOMMUNICATIONS BORROWERS Insurance for Contractors, Engineers, and Architects, Electric Borrowers § 1788.12 Contractors' bonds. Electric borrowers shall require contractors to obtain contractors' bonds when required by part...

  5. Diffusion bonding of mismatch dental alloys.

    PubMed

    Liu, Honghua; Ni, Jiahua; Wu, Luhai; He, Guo

    2010-04-01

    The diffusion bonding of Ti-6Al-4V and Co-Cr-Mo dental alloys has been investigated in terms of the atoms diffusion, the microstructure evolution, and the bonding strength. The bonding performance reveals asymmetry diffusion profiles for both the Co and Cr in Ti-6Al-4V and the Ti in Co-Cr-Mo alloy. Their diffusion coefficients (Arrhenius relations) have been established based on the experiments. Co and Cr diffusion into Ti-6Al-4V leads to alpha --> beta transformation and the intermetallics-formation. Maximum bonding strength occurs at about 840 degrees C. The bonding joint fails under the shear stress in the Ti-6Al-4V side near the bonding interface in brittle manner. The intermetallics in the diffusion layer together with the unbonded areas and other flaws in the bonding interface are responsible for the shear brittle fracture, which also weaken the bonding strength. PMID:19957358

  6. Ultra precision and reliable bonding method

    NASA Technical Reports Server (NTRS)

    Gwo, Dz-Hung (Inventor)

    2001-01-01

    The bonding of two materials through hydroxide-catalyzed hydration/dehydration is achieved at room temperature by applying hydroxide ions to at least one of the two bonding surfaces and by placing the surfaces sufficiently close to each other to form a chemical bond between them. The surfaces may be placed sufficiently close to each other by simply placing one surface on top of the other. A silicate material may also be used as a filling material to help fill gaps between the surfaces caused by surface figure mismatches. A powder of a silica-based or silica-containing material may also be used as an additional filling material. The hydroxide-catalyzed bonding method forms bonds which are not only as precise and transparent as optical contact bonds, but also as strong and reliable as high-temperature frit bonds. The hydroxide-catalyzed bonding method is also simple and inexpensive.

  7. G. N. Lewis and the Chemical Bond.

    ERIC Educational Resources Information Center

    Pauling, Linus

    1984-01-01

    Discusses the contributions of G. N. Lewis to chemistry, focusing on his formulation of the basic principle of the chemical bond--the idea that the chemical bond consists of a pair of electrons held jointly by two atoms. (JN)

  8. Clarifying Chemical Bonding. Overcoming Our Misconceptions.

    ERIC Educational Resources Information Center

    Hapkiewicz, Annis

    1991-01-01

    Demonstrations to help students change their misconceptions about chemical bond breaking are presented. Students' misconceptions about chemical bonds in both biological and chemical systems are discussed. A calculation for the release of energy from respiration is presented. (KR)

  9. 30 CFR 282.40 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... three areas: (1) The Gulf of Mexico and the area offshore the Atlantic Ocean; (2) The area offshore the... Alaska. (g) A separate bond shall be required for each area. An operator's bond may be submitted for...

  10. Analysis of "Kiss" Bonds Between Composite Laminates

    NASA Astrophysics Data System (ADS)

    Poveromo, Scott L.; Earthman, James C.

    2014-06-01

    One of the leading challenges to designing lightweight, cost-effective bonded structures is to detect low shear strength "kiss" bonds where no other defects such as voids and cracks exist. To develop a nondestructive testing method that is sensitive to kiss bonds, standards need to be fabricated with known strength values. In the current work, we attempt to create kiss bonds in between carbon fiber composite laminates that have been bonded with epoxy film adhesive and epoxy paste adhesive. Based on ultrasonic testing, when creating true kiss bonds using film adhesives, a complete disbond could not be avoided because of thermally induced stresses during the high-temperature cure. However, further work demonstrated that kiss bonds can be formed using room-temperature curable epoxy paste adhesives by creating an amine blush on the epoxy surface or applying a release agent on the bonding surfaces.

  11. Eutectic bonding of sapphire to sapphire

    NASA Technical Reports Server (NTRS)

    Deluca, J. J.

    1973-01-01

    Eutectic mixture of aluminum oxide and zirconium oxide provides new bonding technique for sapphires and rubies. Technique effectively reduces possibility of contamination. Bonding material is aluminum oxide and zirconium oxide mixture that matches coefficient of thermal expansion of sapphire.

  12. Tuning reactivity and selectivity in hydrogen atom transfer from aliphatic C-H bonds to alkoxyl radicals: role of structural and medium effects.

    PubMed

    Salamone, Michela; Bietti, Massimo

    2015-11-17

    magnitude. Medium effects on HAT from aliphatic C-H bonds to CumO(•) have been also investigated. With basic substrates, from large to very large decreases in kH have been measured with increasing solvent hydrogen bond donor (HBD) ability or after addition of protic acids or alkali and alkaline earth metal ions, with kinetic effects that exceed 2 orders of magnitude in the reactions of tertiary alkylamines and alkanamides. Solvent hydrogen bonding, protonation, and metal ion binding increase the electron deficiency and the strength of the C-H bonds of these substrates deactivating these bonds toward HAT, with the extent of this deactivation being modulated by varying the nature of the substrate, solvent, protic acid, and metal ion. These results indicate that through these interactions careful control over the HAT reactivity of basic substrates toward CumO(•) and other electrophilic radicals can be achieved, suggesting moreover that these effects can be exploited in an orthogonal fashion for selective C-H bond functionalization of substrates bearing different basic functionalities. PMID:26545103

  13. Approaching improved adhesive bonding repeatability

    NASA Astrophysics Data System (ADS)

    Schlette, Christian; Müller, Tobias; Roβmann, Jürgen; Brecher, Christian

    2016-03-01

    Today, the precision of micro-optics assembly is mostly limited by the accuracy of the bonding process ― and in the case of adhesive bonding by the prediction and compensation of adhesive shrinkage during curing. In this contribution, we present a novel approach to address adhesive bonding based on hybrid control system theory. In hybrid control, dynamic systems are described as "plants" which produce discrete and/or continuous outputs from given discrete and/or continuous inputs, thus yielding a hybrid state space description of the system. The task of hybrid controllers is to observe the plant and to generate a discrete and/or continuous input sequence that guides or holds the plant in a desired target state region while avoiding invalid or unwanted intermediate states. Our approach is based on a series of experiments carried out in order to analyze, define and decouple the dependencies of adhesive shrinkage on multiple parameters, such as application geometries, fixture forces and UV intensities. As some of the dependencies describe continuous effects (e.g. shrinkage from UV intensity) and other dependencies describe discrete state transitions (e.g. fixture removal during curing), the resulting model of the overall bonding process is a hybrid dynamic system in the general case. For this plant model, we then propose a concept of sampling-based parameter search as a basis to design suitable hybrid controllers, which have the potential to optimize process control for a selection of assembly steps, thus improving the repeatability of related production steps like beam-shaping optics or mounting of turning mirrors for fiber coupling.

  14. Controlled double emulsification utilizing 3D PDMS microchannels

    NASA Astrophysics Data System (ADS)

    Chang, Fu-Che; Su, Yu-Chuan

    2008-06-01

    This paper presents a PDMS emulsification device that is capable of generating water-in-oil-in-water double emulsions in a controlled manner. Specially designed 3D microchannels are utilized to steer the independently driven water- and oil-phase flows (especially to restrict the attachment of the middle oil-phase flow on the channel surfaces), and to break the continuous flows into monodisperse double emulsions. In addition to channel geometries and fluid flow rates, surfactants and osmotic agents are employed to facilitate the breakup process and stabilize the resulting emulsion structures. In the prototype demonstration, two-level SU-8 molds were fabricated to duplicate PDMS microstructures, which were surface treated and bonded irreversibly to form 3D microchannels. Throughout the emulsification trials, dripping was intentionally induced to generate monodisperse double emulsions with single or multiple aqueous droplets inside each oil drop. It is found that the overall and core sizes of the resulting double emulsions could be adjusted independently, mainly by varying the outer and inner fluid flow rates, respectively. As such, the presented double emulsification device could potentially realize the controllability on emulsion structure and size distribution, which is desired for a variety of biological and pharmaceutical applications.

  15. 26 CFR 1.142-1 - Exempt facility bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... bonds. (a) Overview. Interest on a private activity bond is not excludable from gross income under section 103(a) unless the bond is a qualified bond. Under section 141(e)(1)(A), an exempt facility bond issued under section 142 may be a qualified bond. Under section 142(a), an exempt facility bond is...

  16. 26 CFR 1.142-1 - Exempt facility bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... bonds. (a) Overview. Interest on a private activity bond is not excludable from gross income under section 103(a) unless the bond is a qualified bond. Under section 141(e)(1)(A), an exempt facility bond issued under section 142 may be a qualified bond. Under section 142(a), an exempt facility bond is...

  17. Bond Percolation on Multiplex Networks

    NASA Astrophysics Data System (ADS)

    Hackett, A.; Cellai, D.; Gómez, S.; Arenas, A.; Gleeson, J. P.

    2016-04-01

    We present an analytical approach for bond percolation on multiplex networks and use it to determine the expected size of the giant connected component and the value of the critical bond occupation probability in these networks. We advocate the relevance of these tools to the modeling of multilayer robustness and contribute to the debate on whether any benefit is to be yielded from studying a full multiplex structure as opposed to its monoplex projection, especially in the seemingly irrelevant case of a bond occupation probability that does not depend on the layer. Although we find that in many cases the predictions of our theory for multiplex networks coincide with previously derived results for monoplex networks, we also uncover the remarkable result that for a certain class of multiplex networks, well described by our theory, new critical phenomena occur as multiple percolation phase transitions are present. We provide an instance of this phenomenon in a multiplex network constructed from London rail and European air transportation data sets.

  18. The Double Chooz Experiment

    NASA Astrophysics Data System (ADS)

    Pfahler, Patrick; Double Chooz Collaboration

    2012-07-01

    Double Chooz is a reactor bar nue-disappearance experiment situated at the commercial nuclear power plant of Chooz in northern France. The experiment aims for the revelation of the last unknown mixing angle Θ13 as a part of the neutrino mixing matrix or the improvement of the upper limit for sin2(2Θ13), which is currently < 0.14 (90% CL). A newly developed gadolinium-loaded liquid scintillator as target allows the detection of electron-anti-neutrinos (bar nue) using the inverse beta decay and its distinct decay pattern (bar nue + p → e+ +n). Double Chooz uses two identical detectors at different distances in order to reduce systematic uncertainties. This will allow, after a data taking phase of 4 years, an improvement on sin2(2Θ13) down to < 0.03 (90% CL). The first (far) detector has successfully been installed and filled, and takes data since April of 2011. A preliminary analysis of first 120 days revealed about 4000 Neutrino-candidates and a stable detector-setup with low backgrounds. The commissioning of the second (near) detector is expected for the beginning of 2013 and will provide maximum sensitivity for the experiment.

  19. On a model of calculating bond strength

    NASA Technical Reports Server (NTRS)

    Yue, A. S.; Yang, T. T.; Lin, T. S.

    1976-01-01

    Diffusion bonding is a fabricating process to join the fibers and a matrix together forming a composite. The efficiency of the bonding process depends on temperature, time, and pressure. Based on a simplified pair potential model, an expression for the bond-energy at the fiber-matrix interface is formulated in terms of the above-mentioned three parameters. From this expression and the mean atomic distance, the bond-strength between the fibers and the matrix can be calculated.

  20. Diffusion bonding of Stratapax for drill bits

    SciTech Connect

    Middleton, J.N.; Finger, J.T.

    1983-01-01

    A process has been developed for the diffusion bonding of General Electric's Stratapax drill blanks to support studs for cutter assemblies in drill bits. The diffusion bonding process is described and bond strength test data are provided for a variety of materials. The extensive process details, provided in the Appendices, should be sufficient to enable others to successfully build diffusion-bonded drill bit cutter assemblies.