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Sample records for electron-deficient double bonds

  1. Chemical bonding in electron-deficient boron oxide clusters: core boronyl groups, dual 3c-4e hypervalent bonds, and rhombic 4c-4e bonds.

    PubMed

    Chen, Qiang; Lu, Haigang; Zhai, Hua-Jin; Li, Si-Dian

    2014-04-28

    We explore the structural and bonding properties of the electron-deficient boron oxide clusters, using a series of B3On(-/0/+) (n = 2-4) clusters as examples. Global-minimum structures of these boron oxide clusters are identified via unbiased Coalescence Kick and Basin Hopping searches, which show a remarkable size and charge-state dependence. An array of new bonding elements are revealed: core boronyl groups, dual 3c-4e hypervalent bonds (ω-bonds), and rhombic 4c-4e bonds (o-bonds). In favorable cases, oxygen can exhaust all its 2s/2p electrons to facilitate the formation of B-O bonds. The current findings should help understand the bonding nature of low-dimensional boron oxide nanomaterials and bulk boron oxides.

  2. Nickel-Catalyzed Insertion of Alkynes and Electron-Deficient Olefins into Unactivated sp(3) C-H Bonds.

    PubMed

    Maity, Soham; Agasti, Soumitra; Earsad, Arif Mahammad; Hazra, Avijit; Maiti, Debabrata

    2015-08-03

    Insertion of unsaturated systems such as alkynes and olefins into unactivated sp(3) C-H bonds remains an unexplored problem. We herein address this issue by successfully incorporating a wide variety of functionalized alkynes and electron-deficient olefins into the unactivated sp(3) C-H bond of pivalic acid derivatives with excellent syn- and linear- selectivity. A strongly chelating 8-aminoquinoline directing group proved beneficial for these insertion reactions, while an air-stable and inexpensive Ni(II) salt has been employed as the active catalyst.

  3. Electron-deficient ruthenium and osmium complexes: From 14-electron species to C-F bond cleavage reactions

    NASA Astrophysics Data System (ADS)

    Huang, Dejian

    1999-12-01

    Stepwise removal of the fluoride from RuRF(CO)L2 gives [RuR(CO)L 2]BAr'4 (L = PtBu 2Me, R = H, CH3, Ph, Ar' = 3,5- bis(trifluoromethyl)phenyl). This 14-electron cation has a saw-horse shape with two bulky L trans and CO and R cis. The two vacant sites are in fact occupied weakly by C-H bonds from the phosphines. [RuH(CO)L2] + has a strong Lewis acidic but weakened π- basic Ru center as it is illustrated by its reactivity pattern towards olefins and alkynes. While organic fluorocarbon is notorious for its inertness due to the strong C-F bond, the α-C-F bond of a transition metal fluorocarbyl complex is activated. The chemistry in Chapter 3 illustrates this argument. Attempts to replace fluoride of MHF(CO)L2 with CF3 using Me 3SiCF3 do not give MH(CF3)(CO)L2, instead, M[HF(CF2)(CO)L2 is isolated. Fast equilibrium exists between RuHF(CF2)(CO)L2 and RuH(CF3)(CO)L 2 but not for OsHF(CF2)(CO)L2, which is converted to OsF2(CFH)(CO)L2 upon heating. In contrast, isomerization of RuHF(CF2)(CO)L2 gives RUF(CF2H)(CO)L 2.

  4. Scope and Mechanisms of Frustrated Lewis Pair Catalyzed Hydrogenation Reactions of Electron-Deficient C=C Double Bonds.

    PubMed

    Morozova, Varvara; Mayer, Peter; Berionni, Guillaume

    2015-11-23

    Several phosphonium and ammonium triarylborohydrides, which are intermediates in hydrogenation reactions catalyzed by frustrated Lewis pairs, were synthesized in high yield under mild conditions from triaryl boranes, ammonium or phosphonium halides, and triethylsilane. The kinetics and mechanisms of the reactions of these hydridoborate salts with benzhydrylium ions, iminium ions, quinone methides, and Michael acceptors were investigated, and their nucleophilicity was determined and compared with that of other hydride donors.

  5. 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…

  6. Theoretical characterization of the sulfilimine bond: Double or single?

    NASA Astrophysics Data System (ADS)

    Pichierri, Fabio

    2010-03-01

    Using quantum mechanical calculations in combination with AIM and NBO analyses, we investigate the properties of the sulfilimine bond, which has been recently detected in collagen IV [Vanacore et al., Science 325 (2009) 1230]. Contrary to the general belief that this is a double bond, -N dbnd S<, our analysis of the wavefunction of a model compound indicates it being a coordinate covalent (dative) single bond, -N ← S<, with a strong polarization towards nitrogen.

  7. A History of the Double-Bond Rule

    NASA Astrophysics Data System (ADS)

    Hoogenboom, Bernard E.

    1998-05-01

    The tautomeric polar systems recognized by Laar in 1886 contain an active atom that appeared to migrate from its original position. The tautomeric systems are of a general structural form and can be represented as X=Y-Z-A. Later workers recognized the same bond weakening effect in a variety of organic structures in which atom A is halogen, hydrogen, carbon, or nitrogen. Hermann Staudinger recognized the weakness of that bond, an allyl bond, in hydrocarbons and exploited the behavior for the preparation of isoprene from terpene hydrocarbons. In 1922 he formulated a generality, a rule, regarding the allyl bond reactivity He noted that natural rubber also decomposed to form isoprene and therefore concluded that natural rubber is an unsaturated hydrocarbon, that isoprene units in natural rubber represent weakly held allyl substituents, and that natural rubber is a macromolecular combination of isoprene units. From his different experience as an industrial chemist, Otto Schmidt recognized the same bond weakening effect in hydrocarbons and in 1932 postulated the "Double-Bond Rule," stating that the presence of a double bond in a hydrocarbon has an alternating strengthening and weakening effect on single bonds throughout the molecule, diminishing with distance from the double bond. Schmidt not only understood the practical benefit of this rule, but he also offered an explanation for the Rule on theoretical grounds. Novel in its time, his theoretical explanation did not find popular acceptance, despite his considerable efforts to promote it in the literature. His concept of the Rule was supplanted by the new theory of resonance devised by Pauling and Wheland and by the implied notion of the stabilization of products by delocalization effects.

  8. Understanding Rotation about a C=C Double Bond

    NASA Astrophysics Data System (ADS)

    Barrows, Susan E.; Eberlein, Thomas H.

    2005-09-01

    In this article, twisting about the C=C double bond and the consequential pyramidalization of sp 2 carbon atoms in alkenes were examined in a molecular modeling study using trans -2-butene as a model system. According to our trans -2-butene model and other similar work, most of the strength of a π bond is retained upon twisting, even for remarkably large C C=C C dihedral angles (up to 90°). The phenomenon of sp 2 carbon atom pyramidalization and preservation of π bond strength upon twisting a C=C double bond is well established in the literature, but is rarely discussed in introductory textbooks. This absence is noteworthy because profound manifestations of this effect do occur in compounds that are covered in an introductory organic chemistry curriculum. We present a simple method of introducing the concept of a flexible C=C π bond into beginning organic chemistry courses. We report the energetic demands of partial twisting about the C=C bond in 2-butene as calculated using DFT, LMP2, and MCSCF methods. Finally, using the results of these calculations, we assessed the degree of strain introduced by the twisted nature of the C=C bond in trans cycloalkenes.

  9. Free radical addition of butanethiol to vegetable oil double bonds.

    PubMed

    Bantchev, Grigor B; Kenar, James A; Biresaw, Girma; Han, Moon Gyu

    2009-02-25

    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 characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Further product characterization and analysis was conducted using GC and GC-MS on the fatty acid methyl esters obtained by the transesterification of the SMVO products. Investigation of the effect of reaction conditions showed that high yield and high conversion of double bonds into thiol were favored at low reaction temperatures and high butanethiol/vegetable oil ratios. Canola and corn oils gave similar double-bond conversions and yields of the desired SMVO product even though they have big differences in the relative numbers of single and multiple double bonds in their structures. Under best reaction conditions, up to 97% of double-bond conversion and 61% isolated yields of the purified SMVO products were attained.

  10. [Determination of double bonds in olive and sunflower oils by ozonize method].

    PubMed

    Evteeva, N M

    2007-01-01

    Kinetics of spending double bonds of tocotherol and accumulation of peroxides during oxidation of olive and sunflower oils were investigated. Date on spending double bonds during oxidation of commercial oils were measured for the first time.

  11. Facile and Promising Method for Michael Addition of Indole and Pyrrole to Electron-Deficient trans-β-Nitroolefins Catalyzed by a Hydrogen Bond Donor Catalyst Feist's Acid and Preliminary Study of Antimicrobial Activity

    PubMed Central

    Al Majid, Abdullah M. A.; Islam, Mohammad Shahidul; Barakat, Assem; Al-Agamy, Mohamed H. M.; Naushad, Mu.

    2014-01-01

    The importance of cooperative hydrogen-bonding effects has been demonstrated using novel 3-methylenecyclopropane-1,2-dicarboxylic acid (Feist's acid (FA)) as hydrogen bond donor catalysts for the addition of indole and pyrrole to trans-β-nitrostyrene derivatives. Because of the hydrogen bond donor (HBD) ability, Feist's acid (FA) has been introduced as a new class of hydrogen bond donor catalysts for the activation of nitroolefin towards nucleophilic substitution reaction. It has effectively catalyzed the Michael addition of indoles and pyrrole to β-nitroolefins under optimum reaction condition to furnish the corresponding Michael adducts in good to excellent yields (up to 98%). The method is general, atom-economical, convenient, and eco-friendly and could provide excellent yields and regioselectivities. Some newly synthesized compounds were for examined in vitro antimicrobial activity and their preliminary results are reported. PMID:24574906

  12. Facile and promising method for michael addition of indole and pyrrole to electron-deficient trans-β-nitroolefins catalyzed by a hydrogen bond donor catalyst Feist's acid and preliminary study of antimicrobial activity.

    PubMed

    Al Majid, Abdullah M A; Islam, Mohammad Shahidul; Barakat, Assem; Al-Agamy, Mohamed H M; Naushad, Mu

    2014-01-01

    The importance of cooperative hydrogen-bonding effects has been demonstrated using novel 3-methylenecyclopropane-1,2-dicarboxylic acid (Feist's acid (FA)) as hydrogen bond donor catalysts for the addition of indole and pyrrole to trans-β-nitrostyrene derivatives. Because of the hydrogen bond donor (HBD) ability, Feist's acid (FA) has been introduced as a new class of hydrogen bond donor catalysts for the activation of nitroolefin towards nucleophilic substitution reaction. It has effectively catalyzed the Michael addition of indoles and pyrrole to β-nitroolefins under optimum reaction condition to furnish the corresponding Michael adducts in good to excellent yields (up to 98%). The method is general, atom-economical, convenient, and eco-friendly and could provide excellent yields and regioselectivities. Some newly synthesized compounds were for examined in vitro antimicrobial activity and their preliminary results are reported.

  13. 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.

  14. Bonding and redox properties of [Os(3)(CO)(9)(tmbp)(L)] (tmbp=4,4',5,5'-tetramethyl-2,2'-biphosphinine; L=CO, PPh(3)) clusters with an unprecedented electron-deficient metallic core and doubly bridging biphosphinine dianion.

    PubMed

    Bakker, Maarten J; Vergeer, Frank W; Hartl, Frantisek; Rosa, Patrick; Ricard, Louis; Le Floch, Pascal; Calhorda, Maria J

    2002-04-02

    Herein we describe in detail the bonding properties and electrochemical behavior of the first known triosmium carbonyl clusters with a coordinated redox-active ligand 4,4',5,5'-tetramethyl-2,2'-biphosphinine (tmbp), the phosphorus derivative of 2,2'-bipyridine. The clusters investigated were [Os(3)(CO)(10)(tmbp)] (1) and its derivative [Os(3)(CO)(9)(PPh(3))(tmbp)] (2). The crystal structures of both clusters are compared with those of relevant compounds; they served as the basis for density functional theory (DFT and time-dependent DFT) calculations. The experimental and theoretical data reveal an unexpected and unprecedented bridging coordination mode of tmbp, with each P atom bridging two metal atoms. The tmbp ligand is formally reduced by transfer of two electrons from the triangular cluster core that consequently lacks one of the metal-metal bonds. Both 1 and 2 therefore represent 50e(-) clusters with a coordinated 8e(-) donor, [tmbp](2-). The HOMO and LUMO of 1 and 2 possess a predominant contribution from different pi*(tmbp) orbitals, implying that the lowest energy excited state possesses a significant intraligand character. This is in agreement with the photostability of these clusters. DFT calculations also predict the experimentally observed structure of 1 to be the most stable one in a series of several plausible structural isomers. Stepwise two-electron electrochemical reduction of 1 and 2 results in dissociation of CO and PPh(3), respectively, and formation of the [Os(3)(CO)(9)(tmbp)](2-) ion. The initially produced radical anions of the parent clusters, in which the odd electron is predominantly localized on the tmbp ligand, are sufficiently stable at low temperatures and can be observed with IR spectroelectrochemistry. The electron-deficiency of the cluster core in 1 permits facile electrocatalytic substitution of a CO ligand by tertiary phosphane and phosphite donors.

  15. Radiation Crosslinking of Polyurethane Enhanced by Introducing Terminal Double-Bonds

    NASA Astrophysics Data System (ADS)

    Zhou, Cheng-Fei; Liu, Yang; Jiu, Yong-Bin; Cao, Wei; Zhai, Tong; Wang, Lian-Cai

    2016-05-01

    In this article, the enhanced radiation crosslinking of polyurethane via double-bond capping method were discussed in detail. Meanwhile, the Enhanced radiation crosslinking of polyurethane based on polyimide as hard segment were emphasized. In addition, the preparation of radiation crosslinking foam by introducing terminal double-bond were introduced.

  16. 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…

  17. 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.

  18. Two-center two-electron covalent bonds with deficient bonding densities.

    PubMed

    Yang, Yang

    2012-10-18

    Electron-deficient covalent bonds are a type of covalent bonds without electron accumulation at their bonding regions. Compared with normal covalent bonds, they are quite sensitive to chemical environments. Electron-deficient and normal covalent bonds are not isolated from each other. An electron-deficient bond may change to a normal one upon the change of substituting groups. Neither bond elongation nor atom electronegativity is directly related to the electron deficiency in an electron-deficient bond. Atoms in molecules (AIM) analyses suggest that electron-deficient bonds are characterized by positive Laplacians and small ρ(BCP) values. The positive Laplacian is caused by insignificant electron accumulation perpendicular to the bond path. On the basis of electron localization function (ELF) descriptors, electron-deficient bonds have small basin populations, low η values and high relative fluctuations. There may be one or two bond basins for an electron-deficient bond. In addition, such a bond may correlate with two more valence basins close to the two participating atoms. Electron-deficient bonds are usually weak and long. This is consistent with the low s characters in their natural bond orbitals (NBOs).

  19. 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.

  20. Pinpointing double bonds in lipids by Paternò-Büchi reactions and mass spectrometry.

    PubMed

    Ma, Xiaoxiao; Xia, Yu

    2014-03-03

    The positions of double bonds in lipids play critical roles in their biochemical and biophysical properties. In this study, by coupling Paternò-Büchi (P-B) reaction with tandem mass spectrometry, we developed a novel method that can achieve confident, fast, and sensitive determination of double bond locations within various types of lipids. The P-B reaction is facilitated by UV irradiation of a nanoelectrospray plume entraining lipids and acetone. Tandem mass spectrometry of the on-line reaction products via collision activation leads to the rupture of oxetane rings and the formation of diagnostic ions specific to the double bond location.

  1. Borohydride-mediated radical addition reactions of organic iodides to electron-deficient alkenes.

    PubMed

    Kawamoto, Takuji; Uehara, Shohei; Hirao, Hidefumi; Fukuyama, Takahide; Matsubara, Hiroshi; Ryu, Ilhyong

    2014-05-02

    Cyanoborohydrides are efficient reagents in the reductive addition reactions of alkyl iodides and electron-deficient olefins. In contrast to using tin reagents, the reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine or carbon-chlorine bond. The reaction system was successfully applied to three-component reactions, including radical carbonylation. The rate constant for the hydrogen abstraction of a primary alkyl radical from tetrabutylammonium cyanoborohydride was estimated to be <1 × 10(4) M(-1) s(-1) at 25 °C by a kinetic competition method. This value is 3 orders of magnitude smaller than that of tributyltin hydride.

  2. A novel palladium-catalyzed hydroalkoxylation of alkenes with a migration of double bond.

    PubMed

    Tan, Jiajing; Zhang, Zuhui; Wang, Zhiyong

    2008-04-21

    A novel palladium-catalyzed addition of alcohols to olefins was developed, in which a migration of double bond was involved. By this new method, a variety of allylic ethers were prepared with moderate to high yields under mild conditions.

  3. Double hydrogen bond mediating self-assembly structure of cyanides on metal surface

    NASA Astrophysics Data System (ADS)

    Wang, Zhongping; Xiang, Feifei; Lu, Yan; Wei, Sheng; Li, Chao; Liu, Xiaoqing; Liu, Lacheng; Wang, Li

    2016-10-01

    Cyanides with different numbers of -C≡N, 1,2,4,5-Tetracyanobenzene (TCNB) and 2,3-Dicyanonaphthalene (2,3-DCN) deposited on Ag(111) and Ag(110) surfaces, have been investigated by room temperature scanning tunneling microscopy (RTSTM), respectively. High resolution STM images show double hydrogen bond is the main driving force to form variety of self-assembly structures, indicating the double hydrogen bond affects the electron distribution of cyanides and leads to a more stable structure with lower energy. In addition, the difference between Ag(111) and Ag(110) surfaces in their lattice structure induces a bigger assembly structural change of 2,3-DCN than that of 1,2,4,5-TCNB, which confirms the fact that the opposite double hydrogen bond formation formed by 1,2,4,5-TCNB is more stable than the neighboring double hydrogen bond formation formed by molecule 2,3-DCN.

  4. α-Halogenoacetanilides as hydrogen-bonding organocatalysts that activate carbonyl bonds: fluorine versus chlorine and bromine.

    PubMed

    Koeller, Sylvain; Thomas, Coralie; Peruch, Fréderic; Deffieux, Alain; Massip, Stéphane; Léger, Jean-Michel; Desvergne, Jean-Pierre; Milet, Anne; Bibal, Brigitte

    2014-03-03

    α-Halogenoacetanilides (X=F, Cl, Br) were examined as H-bonding organocatalysts designed for the double activation of CO bonds through NH and CH donor groups. Depending on the halide substituents, the double H-bond involved a nonconventional CH⋅⋅⋅O interaction with either a HCXn (n=1-2, X=Cl, Br) or a HCAr bond (X=F), as shown in the solid-state crystal structures and by molecular modeling. In addition, the catalytic properties of α-halogenoacetanilides were evaluated in the ring-opening polymerization of lactide, in the presence of a tertiary amine as cocatalyst. The α-dichloro- and α-dibromoacetanilides containing electron-deficient aromatic groups afforded the most attractive double H-bonding properties towards CO bonds, with a NH⋅⋅⋅O⋅⋅⋅HCX2 interaction.

  5. 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.

  6. The Double-Bond Configuration of Corynanthean Alkaloids and Its Impact on Monoterpenoid Indole Alkaloid Biosynthesis.

    PubMed

    Eckermann, Ruben; Gaich, Tanja

    2016-04-11

    Experimental evidence is provided for the coherence of the double-bond geometry and the occurrence of "secondary cyclizations" in the biosynthesis of monoterpenoid indole alkaloids. Biosynthetically, akuammiline, C-mavacurine, and Strychnos alkaloids are proposed to be derived from the corynanthean alkaloid geissoschizine, a key intermediate in the biosynthetic pathway of these monoterpenoid indole alkaloids. This process occurs by so-called "secondary cyclizations" from geissoschizine or its derivatives. Although corynanthean alkaloids like geissoschizine incorporate E or Z double bonds located at C19-C20, the alkaloids downstream in the biosynthesis exclusively exhibit the E double bond. This study shows that secondary cyclizations preferentially occur with the E isomer of geissoschizine or its derivatives. This is attributed to the flexibility of the quinolizidine system of the corynanthean alkaloids, which can adopt a cis or trans conformation. For the secondary cyclization to take place, the cis-quinolizidine conformation is required. Experimental evidence supports the hypothesis that the E double bond of geissoschizine induces the cis conformation, whereas the Z double bond induces the trans conformation, which prohibits secondary cyclization of the Z compounds.

  7. Carbon-carbon double-bond reductases in nature.

    PubMed

    Huang, Minmin; Hu, Haihong; Ma, Li; Zhou, Quan; Yu, Lushan; Zeng, Su

    2014-08-01

    Reduction of C = C bonds by reductases, found in a variety of microorganisms (e.g. yeasts, bacteria, and lower fungi), animals, and plants has applications in the production of metabolites that include pharmacologically active drugs and other chemicals. Therefore, the reductase enzymes that mediate this transformation have become important therapeutic targets and biotechnological tools. These reductases are broad-spectrum, in that, they can act on isolation/conjugation C = C-bond compounds, α,β-unsaturated carbonyl compounds, carboxylic acids, acid derivatives, and nitro compounds. In addition, several mutations in the reductase gene have been identified, some associated with diseases. Several of these reductases have been cloned and/or purified, and studies to further characterize them and determine their structure in order to identify potential industrial biocatalysts are still in progress. In this study, crucial reductases for bioreduction of C = C bonds have been reviewed with emphasis on their principal substrates and effective inhibitors, their distribution, genetic polymorphisms, and implications in human disease and treatment.

  8. Double-bond-containing polyallene-based triblock copolymers via phenoxyallene and (meth)acrylate.

    PubMed

    Ding, Aishun; Lu, Guolin; Guo, Hao; Huang, Xiaoyu

    2017-03-02

    A series of ABA triblock copolymers, consisting of double-bond-containing poly(phenoxyallene) (PPOA), poly(methyl methacrylate) (PMMA), or poly(butyl acrylate) (PBA) segments, were synthesized by sequential free radical polymerization and atom transfer radical polymerization (ATRP). A new bifunctional initiator bearing azo and halogen-containing ATRP initiating groups was first prepared followed by initiating conventional free radical homopolymerization of phenoxyallene with cumulated double bond to give a PPOA-based macroinitiator with ATRP initiating groups at both ends. Next, PMMA-b-PPOA-b-PMMA and PBA-b-PPOA-b-PBA triblock copolymers were synthesized by ATRP of methyl methacrylate and n-butyl acrylate initiated by the PPOA-based macroinitiator through the site transformation strategy. These double-bond-containing triblock copolymers are stable under UV irradiation and free radical circumstances.

  9. Double-bond-containing polyallene-based triblock copolymers via phenoxyallene and (meth)acrylate

    NASA Astrophysics Data System (ADS)

    Ding, Aishun; Lu, Guolin; Guo, Hao; Huang, Xiaoyu

    2017-03-01

    A series of ABA triblock copolymers, consisting of double-bond-containing poly(phenoxyallene) (PPOA), poly(methyl methacrylate) (PMMA), or poly(butyl acrylate) (PBA) segments, were synthesized by sequential free radical polymerization and atom transfer radical polymerization (ATRP). A new bifunctional initiator bearing azo and halogen-containing ATRP initiating groups was first prepared followed by initiating conventional free radical homopolymerization of phenoxyallene with cumulated double bond to give a PPOA-based macroinitiator with ATRP initiating groups at both ends. Next, PMMA-b-PPOA-b-PMMA and PBA-b-PPOA-b-PBA triblock copolymers were synthesized by ATRP of methyl methacrylate and n-butyl acrylate initiated by the PPOA-based macroinitiator through the site transformation strategy. These double-bond-containing triblock copolymers are stable under UV irradiation and free radical circumstances.

  10. Double-bond-containing polyallene-based triblock copolymers via phenoxyallene and (meth)acrylate

    PubMed Central

    Ding, Aishun; Lu, Guolin; Guo, Hao; Huang, Xiaoyu

    2017-01-01

    A series of ABA triblock copolymers, consisting of double-bond-containing poly(phenoxyallene) (PPOA), poly(methyl methacrylate) (PMMA), or poly(butyl acrylate) (PBA) segments, were synthesized by sequential free radical polymerization and atom transfer radical polymerization (ATRP). A new bifunctional initiator bearing azo and halogen-containing ATRP initiating groups was first prepared followed by initiating conventional free radical homopolymerization of phenoxyallene with cumulated double bond to give a PPOA-based macroinitiator with ATRP initiating groups at both ends. Next, PMMA-b-PPOA-b-PMMA and PBA-b-PPOA-b-PBA triblock copolymers were synthesized by ATRP of methyl methacrylate and n-butyl acrylate initiated by the PPOA-based macroinitiator through the site transformation strategy. These double-bond-containing triblock copolymers are stable under UV irradiation and free radical circumstances. PMID:28252049

  11. Access to B=S and B=Se double bonds via sulfur and selenium insertion into a B-H bond and hydrogen migration.

    PubMed

    Wang, Hao; Zhang, Jianying; Hu, Hongfan; Cui, Chunming

    2010-08-18

    Stable compounds with a boron-chalcogen (S or Se) valence double bond have been prepared via sequences involving insertion of the chalcogen into a B-H bond and subsequent hydrogen migration. X-ray diffraction studies and density functional theory calculations on the resulting compounds provide convincing evidence for the boron-chalcogen multiple bonding.

  12. On the existence of Si-C double bonded graphene-like layers

    NASA Astrophysics Data System (ADS)

    Huda, Muhammad N.; Yan, Yanfa; Al-Jassim, Mowafak M.

    2009-09-01

    Upon analyzing an earlier experimental study by density-functional theory we have shown that graphene-like SiC layers can exist. We found that, for a particular stacking sequence, Si dbnd C double bond was responsible for the much larger interlayer distances observed in synthesized multi-walled SiC nanotubes. The Si/C ratios in SiC layers determine the extent of interlayer distances and bonding nature. It has been also shown that for some intermediate ratios of Si:C and/or with other stacking sequences, a collapse of SiC layers to tetrahedrally bonded system is possible. We have argued that these synthesized Si dbnd C double-bonded multi-wall silicon-carbide nanotubes may provide a pathway for future realization of SiC graphene-like materials.

  13. 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.

  14. Double bonding system for deeply impacted tooth--a technic clinic.

    PubMed

    Singh, Gyan P; Tandon, Pradeep; Shastri, Dipti; Verma, Sneh Lata; Verma, Sneh Lata; Verma, Umesh P

    2013-01-01

    Close eruption technique is preferred in deep, buried, intraosseous and labially impacted teeth to provide healthy and fuinctional attached gingiva but in this technique failure of bonded attachment usually means, repeat exposure of the impacted tooth. This article describes an innovative method for bonding two attachments (Double Bonding System) in combination instead of one. It provides the safe and determinate system for ortho-eruption, avoid the trauma of patient from re-exposure and enhance the comfort as well the confidence of the operator.

  15. Reduction of carbon-carbon double bonds using organocatalytically generated diimide.

    PubMed

    Smit, Christian; Fraaije, Marco W; Minnaard, Adriaan J

    2008-12-05

    An efficient method has been developed for the reduction of carbon-carbon double bonds with diimide, catalytically generated in situ from hydrazine hydrate. The employed catalyst is prepared in one step from riboflavin (vitamin B(2)). Reactions are carried out in air and are a valuable alternative when metal-catalyzed hydrogenations are problematic.

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

    PubMed

    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, D1/D2, 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 D2 = D1 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.

  17. Using ambient ozone for assignment of double bond position in unsaturated lipids.

    PubMed

    Ellis, Shane R; Hughes, Jessica R; Mitchell, Todd W; in het Panhuis, Marc; Blanksby, Stephen J

    2012-03-07

    Unsaturated lipids deposited onto a range of materials are observed to react with the low concentrations of ozone present in normal laboratory air. Parent lipids and ozonolysis cleavage products are both detected directly from surfaces by desorption electrospray ionisation mass spectrometry (DESI-MS) with the resulting mass spectra providing clear evidence of the double bond position within these molecules. This serendipitous process has been coupled with thin-layer chromatography (TLC) to provide a simple but powerful approach for the detailed structural elucidation of lipids present in complex biological extracts. Lipid extracts from human lens were deposited onto normal phase TLC plates and then developed to separate components according to lipid class. Exposure of the developed plates to laboratory air for ca. 1 h prior to DESI-MS analysis gave rise to ozonolysis products allowing for the unambiguous identification of double bond positions in even low abundant, unsaturated lipids. In particular, the co-localization of intact unsaturated lactosylceramides (LacCer) with products from their oxidative cleavage provide the first evidence for the presence of three isomeric LacCer (d18:0/24:1) species in the ocular lens lipidome, i.e., variants with double bonds at the n-9, n-7 and n-5 positions.

  18. Hydrogen Bonding in 4-AMINOPHENYL Ethanol: a Combined Ir-Uv Double Resonance and Microwave Study

    NASA Astrophysics Data System (ADS)

    Bray, Caitlin; Rivera, Cara Rae; Arsenault, E. A.; Obenchain, Daniel A.; Novick, Stewart E.; Knee, Joseph L.

    2015-06-01

    Both amine and hydroxyl functional groups are present in 4-aminophenyl ethanol (4-AE), and each functional group can form hydrogen bonds with carboxylic acids, such as formic acid and acetic acid. Predicting the structures of such complexes involving 4-AE is rather complex, given the many possible conformations and their similar (and method and basis-dependent) energies. In particular, the carboxyl group, -COOH, can act as both as a hydrogen bond donor or acceptor, or both at once. In this study we report the formic acid - 4-AE hydrogen bonded complex. An infrared-ultraviolet double resonance spectrometer is used to examine the shifts in IR frequencies of 4-AE from the monomer to the complex. Fourier transform microwave spectroscopy is used to determine structures of the species. Results from both experiments are compared to DFT and ab initio results. Time permitting, results of the water complex with 4-AE will also be presented.

  19. 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

  20. Rhodium-catalyzed enantioselective cyclopropanation of electron deficient alkenes

    PubMed Central

    Wang, Hengbin; Guptill, David M.; Alvarez, Adrian Varela

    2013-01-01

    The rhodium-catalyzed reaction of electron-deficient alkenes with substituted aryldiazoacetates and vinyldiazoacetates results in highly stereoselective cyclopropanations. With adamantylglycine derived catalyst Rh2(S-TCPTAD)4, high asymmetric induction (up to 98% ee) can be obtained with a range of substrates. Computational studies suggest that the reaction is facilitated by weak interaction between the carbenoid and the substrate carbonyl but subsequently proceeds via different pathways depending on the nature of the carbonyl.. Acrylates and acrylamides result in the formation of cyclopropanation products while the use of unsaturated aldehydes and ketones results in the formation of epoxides. PMID:24049630

  1. Single Molecule Study of Force-Induced Rotation of Carbon-Carbon Double Bonds in Polymers.

    PubMed

    Huang, Wenmao; Zhu, Zhenshu; Wen, Jing; Wang, Xin; Qin, Meng; Cao, Yi; Ma, Haibo; Wang, Wei

    2017-01-24

    Carbon-carbon double bonds (C═C) are ubiquitous in natural and synthetic polymers. In bulk studies, due to limited ways to control applied force, they are thought to be mechanically inert and not to contribute to the extensibility of polymers. Here, we report a single molecule force spectroscopy study on a polymer containing C═C bonds using atomic force microscope. Surprisingly, we found that it is possible to directly observe the cis-to-trans isomerization of C═C bonds at the time scale of ∼1 ms at room temperature by applying a tensile force ∼1.7 nN. The reaction proceeds through a diradical intermediate state, as confirmed by both a free radical quenching experiment and quantum chemical modeling. The force-free activation length to convert the cis C═C bonds to the transition state is ∼0.5 Å, indicating that the reaction rate is accelerated by ∼10(9) times at the transition force. On the basis of the density functional theory optimized structure, we propose that because the pulling direction is not parallel to C═C double bonds in the polymer, stretching the polymer not only provides tension to lower the transition barrier but also provides torsion to facilitate the rotation of cis C═C bonds. This explains the apparently low transition force for such thermally "forbidden" reactions and offers an additional explanation of the "lever-arm effect" of polymer backbones on the activation force for many mechanophores. This work demonstrates the importance of precisely controlling the force direction at the nanoscale to the force-activated reactions and may have many implications on the design of stress-responsive materials.

  2. Friedel-Crafts Coupling of Electron-Deficient Benzoylacetones Tuned by Remote Electronic Effects.

    PubMed

    Luo, Hongmei; Pan, Ling; Xu, Xianxiu; Liu, Qun

    2015-08-21

    Acid-catalyzed electrophilic aromatic substitution for C-C bond formation, commonly referred to as the Friedel-Crafts reaction in recognition of its discoverers, has been one of the most useful reactions in organic chemistry for over a century. However, the Friedel-Crafts reaction cannot occur on a benzene ring having a strongly electron withdrawing group, such as an acyl group, which deactivates the aromatic ring toward electrophilic substitutions and remains a major challenge. Herein, the synthesis of naphthoquinones and 1,3-indandiones, bearing two acyl groups at positions ortho to each other on a benzene ring, are demonstrated by means of copper-catalyzed intramolecular aerobic oxidative acylation of benzoylacetone derivative precursors. This unusual Friedel-Crafts reaction reveals a new activation mode for the in situ polarity reverse of an electron-deficient aromatic ring to a reactive, electron-rich ring tuned by remote electronic effects.

  3. Atmospheric chemistry of Z- and E-CF3CH[double bond, length as m-dash]CHCF3.

    PubMed

    Østerstrøm, Freja F; Andersen, Simone Thirstrup; Sølling, Theis I; Nielsen, Ole John; Sulbaek Andersen, Mads P

    2016-12-21

    The atmospheric fates of Z- and E-CF3CH[double bond, length as m-dash]CHCF3 have been studied, investigating the kinetics and the products of the reactions of the two compounds with Cl atoms, OH radicals, OD radicals, and O3. FTIR smog chamber experiments measured: k(Cl + Z-CF3CH[double bond, length as m-dash]CHCF3) = (2.59 ± 0.47) × 10(-11), k(Cl + E-CF3CH[double bond, length as m-dash]CHCF3) = (1.36 ± 0.27) × 10(-11), k(OH + Z-CF3CH[double bond, length as m-dash]CHCF3) = (4.21 ± 0.62) × 10(-13), k(OH + E-CF3CH[double bond, length as m-dash]CHCF3) = (1.72 ± 0.42) × 10(-13), k(OD + Z-CF3CH[double bond, length as m-dash]CHCF3) = (6.94 ± 1.25) × 10(-13), k(OD + E-CF3CH[double bond, length as m-dash]CHCF3) = (5.61 ± 0.98) × 10(-13), k(O3 + Z-CF3CH[double bond, length as m-dash]CHCF3) = (6.25 ± 0.70) × 10(-22), and k(O3 + E-CF3CH[double bond, length as m-dash]CHCF3) = (4.14 ± 0.42) × 10(-22) cm(3) molecule(-1) s(-1) in 700 Torr of air/N2/O2 diluents at 296 ± 2 K. E-CF3CH[double bond, length as m-dash]CHCF3 reacts with Cl atoms to give CF3CHClC(O)CF3 in a yield indistinguishable from 100%. Z-CF3CH[double bond, length as m-dash]CHCF3 reacts with Cl atoms to give (95 ± 10)% CF3CHClC(O)CF3 and (7 ± 1)% E-CF3CH[double bond, length as m-dash]CHCF3. CF3CHClC(O)CF3 reacts with Cl atoms to give the secondary product CF3C(O)Cl in a yield indistinguishable from 100%, with the observed co-products C(O)F2 and CF3O3CF3. The main atmospheric fate for Z- and E-CF3CH[double bond, length as m-dash]CHCF3 is reaction with OH radicals. The atmospheric lifetimes of Z- and E-CF3CH[double bond, length as m-dash]CHCF3 are estimated as 27 and 67 days, respectively. IR absorption cross sections are reported and the global warming potentials (GWPs) of Z- and E-CF3CH[double bond, length as m-dash]CHCF3 for the 100 year time horizon are calculated to be GWP100 = 2 and 7, respectively. This study provides a comprehensive description of the atmospheric fate and impact of Z- and E

  4. 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

    2016-08-04

    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.

  5. A fusion of the closed-shell coupled cluster singles and doubles method and valence-bond theory for bond breaking.

    PubMed

    Small, David W; Head-Gordon, Martin

    2012-09-21

    Closed-shell coupled cluster singles and doubles (CCSD) is among the most important of electronic-structure methods. However, it fails qualitatively when applied to molecular systems with more than two strongly correlated electrons, such as those with stretched or broken covalent bonds. We show that it is possible to modify the doubles amplitudes to obtain a closed-shell CCSD method that retains the computational cost and desirable features of standard closed-shell CCSD, e.g., correct spin symmetry, size extensivity, orbital invariance, etc., but produces greatly improved energies upon bond dissociation of multiple electron pairs; indeed, under certain conditions the dissociation energies are exact.

  6. Restorative resins: hardness and strength vs. quantity of remaining double bonds.

    PubMed

    Asmussen, E

    1982-12-01

    It has been hypothesized that the Wallace indentation hardness of smooth surface resins is a factor of prime importance for the abrasion by food of Class 1 restorations. In the present work factors affecting the hardness of polymers were investigated. In addition the tensile strength of composite resins was measured and related to the catalytic system of the polymer. It was found that for a given composition of the monomer the Wallace hardness number increased with increasing content of inhibitor, decreased with increasing content of peroxide, and was unaffected by changes in the content of amine. The hardness was well correlated with the quantity of double bonds remaining in the polymer. BISGMA-based polymers showed no variation in hardness when the originating monomer varied with respect to content of a bi- or a trifunctional diluting monomer. Light-polymerized polymers were relatively hard as compared to chemically cured materials of adequate setting time. The tensile strength of composite resins was predominantly determined by the monomer content of peroxide and increased herewith. The tensile strength was well correlated with the quantity of remaining double bonds in the constituting polymer.

  7. The direct determination of double bond positions in lipid mixtures by liquid chromatography/in-line ozonolysis/mass spectrometry.

    PubMed

    Sun, Chenxing; Zhao, Yuan-Yuan; Curtis, Jonathan M

    2013-01-31

    The direct determination of double bond positions in unsaturated lipids using in-line ozonolysis-mass spectrometry (O(3)-MS) is described. In this experiment, ozone penetrates through the semi-permeable Teflon AF-2400 tubing containing a flow of a solution of fatty acid methyl esters (FAME). Unsaturated FAME are thus oxidized by the ozone and cleaved at the double bond positions. The ozonolysis products then flow directly into the atmospheric pressure photoionization (APPI) source of a mass spectrometer for analysis. Aldehyde products retaining the methyl ester group are indicative of the double bond positions in unsaturated FAME. For the first time, O(3)-MS is able to couple directly to high performance liquid chromatography (HPLC), making the double bond localization in lipid mixtures possible. The application of LC/O(3)-MS has been demonstrated for a fat sample from bovine adipose tissue. A total of 9 unsaturated FAME including 6 positional isomers were identified unambiguously, without comparison to standards. The in-line ozonolysis reaction apparatus is applicable to most mass spectrometers without instrumental modification; it is also directly compatible with various LC columns. The LC/O(3)-MS method described here is thus a practical, versatile and easy to use new approach to the direct determination of double bond positions in lipids, even in complex mixtures.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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 Sr2FeMoO6 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 eg and t2g electrons from Fe and Mo atoms. Those peaks were tagged as bonding or antibonding around the Fermi level at both, valence and conduction bands.

  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. Importance of the sphingosine base double-bond geometry for the structural and thermodynamic properties of sphingomyelin bilayers.

    PubMed

    Janosi, Lorant; Gorfe, Alemayehu

    2010-11-03

    The precise role of the sphingosine base trans double bond for the unique properties of sphingomyelins (SMs), one of the main lipid components in raftlike structures of biological membranes, has not been fully explored. Several reports comparing the hydration, lipid packing, and hydrogen-bonding behaviors of SM and glycerophospholipid bilayers found remarkable differences overall. However, the atomic interactions linking the double-bond geometry with these thermodynamic and structural changes remained elusive. A recent report on ceramides, which differ from SMs only by their hydroxyl headgroup, has shown that replacing the trans double bond of the sphingosine base by cis weakens the hydrogen-bonding potential of these lipids and thereby alters their biological activity. Based on data from extensive (a total 0.75 μs) atomistic molecular dynamics simulations of bilayers composed of all-trans, all-cis, and a trans/cis (4:1 ratio) racemic mixture of sphingomyelin lipids, here we show that the trans configuration allows for the formation of significantly more hydrogen bonds than the cis. The extra hydrogen bonds enabled tighter packing of lipids in the all-trans and trans/cis bilayers, thus reducing the average area per lipid while increasing the chain order and the bilayer thickness. Moreover, fewer water molecules access the lipid-water interface of the all-trans bilayer than of the all-cis bilayer. These results provide the atomic basis for the importance of the natural sphingomyelin trans double-bond conformation for the formation of ordered membrane domains.

  12. Nuclear magnetic resonance and molecular modeling study of exocyclic carbon-carbon double bond polarization in benzylidene barbiturates

    NASA Astrophysics Data System (ADS)

    Figueroa-Villar, J. Daniel; Vieira, Andreia A.

    2013-02-01

    Benzylidene barbiturates are important materials for the synthesis of heterocyclic compounds with potential for the development of new drugs. The reactivity of benzylidene barbiturates is mainly controlled by their exocyclic carbon-carbon double bond. In this work, the exocyclic double bond polarization was estimated experimentally by NMR and correlated with the Hammett σ values of the aromatic ring substituents and the molecular modeling calculated atomic charge difference. It is demonstrated that carbon chemical shift differences and NBO charge differences can be used to predict their reactivity.

  13. Thermodynamic analysis of chain-melting transition temperatures for monounsaturated phospholipid membranes: dependence on cis-monoenoic double bond position.

    PubMed Central

    Marsh, D

    1999-01-01

    Unsaturated phospholipid is the membrane component that is essential to the dynamic environment needed for biomembrane function. The dependence of the chain-melting transition temperature, T(t), of phospholipid bilayer membranes on the position, n(u), of the cis double bond in the glycerophospholipid sn-2 chain can be described by an expression of the form T(t) = T(t)(c)(1 + h'(c)|n(u) - n(c)|)/(1 + s'(c)|n(u) - n(c)|), where n(c) is the chain position of the double bond corresponding to the minimum transition temperature, T(t)(c), for constant diacyl lipid chain lengths. This implies that the incremental transition enthalpy (and entropy) contributed by the sn-2 chain is greater for whichever of the chain segments, above or below the double-bond position, is the longer. The critical position, n(c), of the double bond is offset from the center of the sn-2 chain by an approximately constant amount, deltan(c) approximately 1. 5 C-atom units. The dependence of the parameters T(t)(c), h'(c), and s'(c) on sn-1 and sn-2 chain lengths can be interpreted consistently when allowance is made for the chain packing mismatch between the sn-1 and sn-2 chains. The length of the sn-2 chain is reduced by approximately 0.8 C-atom units by the cis double bond, in addition to a shortening by approximately 1.3 C-atom units by the bent configuration at the C-2 position. Based on this analysis, a general thermodynamic expression is proposed for the dependence of the chain-melting transition temperature on the position of the cis double bond and on the sn-1 and sn-2 chain lengths. The above treatment is restricted mostly to double-bond positions close to the center of the sn-2 chain. For double bonds positioned closer to the carboxyl or terminal methyl ends of the sn-2 chain, the effects on transition enthalpy can be considerably larger. They may be interpreted by the same formalism, but with different characteristic parameters, h'(c) and s'(c), such that the shorter of the chain segments

  14. Ozone-induced dissociation: elucidation of double bond position within mass-selected lipid ions.

    PubMed

    Thomas, Michael C; Mitchell, Todd W; Harman, David G; Deeley, Jane M; Nealon, Jessica R; Blanksby, Stephen J

    2008-01-01

    Ions formed from lipids during electrospray ionization of crude lipid extracts have been mass-selected within a quadrupole linear ion trap mass spectrometer and allowed to react with ozone vapor. Gas-phase ion-molecule reactions between unsaturated lipid ions and ozone are found to yield two primary product ions for each carbon-carbon double bond within the molecule. The mass-to-charge ratios of these chemically induced fragments are diagnostic of the position of unsaturation within the precursor ion. This novel analytical technique, dubbed ozone-induced dissociation (OzID), can be applied both in series and in parallel with conventional collision-induced dissociation (CID) to provide near-complete structural assignment of unknown lipids within complex mixtures without prior fractionation or derivatization. In this study, OzID is applied to a suite of complex lipid extracts from sources including human lens, bovine kidney, and commercial olive oil, thus demonstrating the technique to be applicable to a broad range of lipid classes including both neutral and acidic glycerophospholipids, sphingomyelins, and triacylglycerols. Gas-phase ozonolysis reactions are also observed with different types of precursor ions including [M+H]+, [M+Li]+, [M+Na]+, and [M-H]-: in each case yielding fragmentation data that allow double bond position to be unambiguously assigned. Within the human lens lipid extract, three sphingomyelin regioisomers, namely SM(d18:0/15Z-24:1), SM(d18:0/17Z-24:1), and SM(d18:0/19Z-24:1), and a novel phosphatidylethanolamine alkyl ether, GPEtn(11Z-18:1e/9Z-18:1), are identified using a combination of CID and OzID. These discoveries demonstrate that lipid identification based on CID alone belies the natural structural diversity in lipid biochemistry and illustrate the potential of OzID as a complementary approach within automated, high-throughput lipid analysis protocols.

  15. Conjugated Double Bonds in Lipid Bilayers: A Molecular Dynamic Simulation Study

    PubMed Central

    Zhao, Guijun; Subbaiah, P. V.; Chiu, See-Wing; Jakobsson, Eric; Scott, H. L.

    2011-01-01

    Conjugated linoleic acids (CLA) are found naturally in dairy products. Two isomers of CLA, that differ only in the location of cis and trans double bonds, are found to have distinct and different biological effects. The cis 9 trans 11 (C9T11) isomer is attributed to have the anti-carcinogenic effects, while the trans 10 cis 12 (T10C12) isomer is believed to be responsible for the anti-obesity effects. Since dietary CLA are incorporated into membrane phospholipids, we have used Molecular Dynamics (MD) simulations to investigate the comparative effects of the two isomers on lipid bilayer structure. Specifically, simulations of phosphatidylcholine lipid bilayers in which the sn-2 chains contained one of the two isomers of CLA were performed. Force field parameters for the torsional potential of double bonds were obtained from ab initio calculations. From the MD trajectories we calculated and compared structural properties of the two lipid bilayers, including areas per molecule, density profiles, thickness of bilayers, tilt angle of tail chains, order parameters profiles, radial distribution function (RDF) and lateral pressure profiles. The main differences found between bilayers of the two CLA isomers, are (1) the order parameter profile for C9T11 has a dip in the middle of sn-2 chain while the profile for T10C12 has a deeper dip close to terminal of sn-2 chain, and (2) the lateral pressure profiles show differences between the two isomers. Our simulation results reveal localized physical structural differences between bilayers of the two CLA isomers that may contribute to different biological effects through differential interactions with membrane proteins or cholesterol. PMID:21320475

  16. Biocatalytic Asymmetric Alkene Reduction: Crystal Structure and Characterization of a Double Bond Reductase from Nicotiana tabacum

    PubMed Central

    2013-01-01

    The application of biocatalysis for the asymmetric reduction of activated C=C is a powerful tool for the manufacture of high-value chemical commodities. The biocatalytic potential of “-ene” reductases from the Old Yellow Enzyme (OYE) family of oxidoreductases is well-known; however, the specificity of these enzymes toward mainly small molecule substrates has highlighted the need to discover “-ene” reductases from different enzymatic classes to broaden industrial applicability. Here, we describe the characterization of a flavin-free double bond reductase from Nicotiana tabacum (NtDBR), which belongs to the leukotriene B4 dehydrogenase (LTD) subfamily of the zinc-independent, medium chain dehydrogenase/reductase superfamily of enzymes. Using steady-state kinetics and biotransformation reactions, we have demonstrated the regio- and stereospecificity of NtDBR against a variety of α,β-unsaturated activated alkenes. In addition to catalyzing the reduction of typical LTD substrates and several classical OYE-like substrates, NtDBR also exhibited complementary activity by reducing non-OYE substrates (i.e., reducing the exocyclic C=C double bond of (R)-pulegone) and in some cases showing an opposite stereopreference in comparison with the OYE family member pentaerythritol tetranitrate (PETN) reductase. This serves to augment classical OYE “-ene” reductase activity and, coupled with its aerobic stability, emphasizes the potential industrial value of NtDBR. Furthermore, we also report the X-ray crystal structures of the holo-, binary NADP(H)-bound, and ternary [NADP+ and 4-hydroxy-3-methoxycinnamaldehyde (9a)-bound] NtDBR complexes. These will underpin structure-driven site-saturated mutagenesis studies aimed at enhancing the reactivity, stereochemistry, and specificity of this enzyme. PMID:27547488

  17. Influence of chain length and double bond on the aqueous behavior of choline carboxylate soaps.

    PubMed

    Rengstl, Doris; Diat, Olivier; Klein, Regina; Kunz, Werner

    2013-02-26

    In preceding studies, we demonstrated that choline carboxylates ChC(m) with alkyl chain lengths of m = 12 - 18 are highly water-soluble (for m = 12, soluble up to 93 wt % soap and 0 °C). In addition, choline soaps are featured by an extraordinary lyotropic phase behavior. With decreasing water concentration, the following phases were found: micellar phase (L(1)), discontinuous cubic phase (I(1)' and I(1)"), hexagonal phase (H(1)), bicontinuous cubic phase (V(1)), and lamellar phase (L(α)). The present work is also focused on the lyotropic phase behavior of choline soaps but with shorter alkyl chains or different alkyl chain properties. We have investigated the aqueous phase behavior of choline soaps with C(8) and C(10) chain-lengths (choline octanoate and choline decanoate) and with a C(18) chain-length with a cis-double bond (choline oleate). We found that choline decanoate follows the lyotropic phase behavior of the longer-chain homologues mentioned above. Choline octanoate in water shows no discontinuous cubic phases, but an extended, isotropic micellar solution phase. In addition, choline octanoate is at the limit between a surfactant and a hydrotrope. The double bond in choline oleate leads also to a better solubility in water and a decrease of the solubilization temperature. It also influences the Gaussian curvature of the aggregates which results in a loss of discontinuous cubic phases in the binary phase diagram. The different lyotropic mesophases were identified by the penetration scan technique with polarizing light microscope and visual observations. To clarify the structural behavior small (SAXS) and wide (WAXS) angle X-ray scattering were performed. To further characterize the extended, isotropic micellar solution phase in the binary phase diagram of choline octanoate viscosity and conductivity measurements were also carried out.

  18. 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.

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

    DOE PAGES

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

    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

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

    PubMed

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

    2015-09-21

    [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.

  1. A new fluorogenic sensing platform for salicylic acid derivatives based on π-π and NH-π interactions between electron-deficient and electron-rich aromatics.

    PubMed

    Pandith, Anup; Hazra, Giridhari; Kim, Hong-Seok

    2017-02-03

    A novel simple fluorescent probe was designed for the recognition of electron-rich salicylic acid derivatives (SAs). The imidazole-appended aminomethyl perylene probe 1 selectively differentiated between electron-rich amino-SAs and electron-deficient nitro-SAs in EtOH, exhibiting the highest selectivity and sensitivity toward 5-aminosalicylic acid (5-ASA) and showing strong 1:1 binding (Ka=1.37×10(7)M(-1)). This high selectivity and sensitivity resulted from the synergistic multiple hydrogen bonding interactions of secondary amine and imidazole units and π-π interactions between electron-rich and electron-deficient rings, along with the unusual NH-π interactions between 5-ASA and the perylene moiety of 1. The limit of detection (LOD) for 5-ASA in EtOH was 0.012ppb.

  2. 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)

  3. The unexpected mechanism of carbonyl hydrosilylation catalyzed by (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)).

    PubMed

    Shirobokov, Oleg G; Gorelsky, Serge I; Simionescu, Razvan; Kuzmina, Lyudmila G; Nikonov, Georgii I

    2010-11-07

    Complex (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)) (2, Ar = 2,6-diisopropylphenyl) catalyzes the hydrosilylation of carbonyls by an unexpected associative mechanism. Complex 2 also reacts with PhSiH(3) by a σ-bond metathesis mechanism to give the silyl derivative (Cp)(ArN[double bond, length as m-dash])Mo(SiH(2)Ph)(PMe(3)).

  4. THE PROTOTYPE ALUMINUM - CARBON SINGLE, DOUBLE, AND TRIPLE BONDS: Al - CH3, Al = CH2, AND Al. = CH

    SciTech Connect

    Fox, Douglas J.; Ray, Douglas; Rubesin, Philip C.; Schaefer III, Henry F.

    1980-06-01

    Nonempirical quantum mechanical methods have been used to investigate the A{ell}CH{sub 3}, A{ell}CH{sub 2}, and A{ell}CH molecules, which may be considered to represent the simplest aluminum-carbon single, double, and triple bonds. Equilibrium geometries and vibrational frequencies were determined at the self-consistent-field level of theory using double zeta basis set: A{ell}(11s7p/6s4p), C(9s5p/4s2p), H(4s/2s). The {sup 1}A{sub 1} ground state of A{ell}CH{sub 3} has a reasonably conventional A{ell}-C single bond of length 2.013 {angstrom}, compared to 1.96 {angstrom} in the known molecule A{ell}(CH{sub 3}){sub 3}. The CH equilibrium distance is 1.093 {angstrom} and the A{ell}-C-H angle 111.9{sup o}. The structures of three electron states each of A{ell}CH{sub 2} and A{ell}CH were similarly predicted, The interesting result is that the ground state of A{ell}CH{sub 2} does not contain an A{ell}-C double bond, and the ground state of A{ell}CH is not characterized by an A{ell}{triple_bond}C bond. The multiply-bonded electronic states do exist but they lie 21 kcal (A{ell}CH{sub 2}) and 86 kcal (A{ell}CH) above the respective ground states. The dissociation energies of the three ground electronic states are predicted to be 68 kcal (A{ell}CH{sub 3}), 77 kcal (A{ell}CH{sub 2}), and 88 kcal (A{ell}CH), Vibrational frequencies are also predicted for the three molecules, and their electronic structures are discussed with reference to Mulliken populations and dipole moments.

  5. Fabrication of extremely thermal-stable GaN template on Mo substrate using double bonding and step annealing process

    NASA Astrophysics Data System (ADS)

    Qing, Wang; Yang, Liu; Yongjian, Sun; Yuzhen, Tong; Guoyi, Zhang

    2016-08-01

    A new layer transfer technique which comprised double bonding and a step annealing process was utilized to transfer the GaN epilayer from a sapphire substrate to a Mo substrate. Combined with the application of the thermal-stable bonding medium, the resulting two-inch-diameter GaN template showed extremely good stability under high temperature and low stress state. Moreover, no cracks and winkles were observed. The transferred GaN template was suitable for homogeneous epitaxial, thus could be used for the direct fabrication of vertical LED chips as well as power electron devices. It has been confirmed that the double bonding and step annealing technique together with the thermal-stable bonding layer could significantly improve the bonding strength and stress relief, finally enhancing the thermal stability of the transferred GaN template. Project supported by the Guangdong Innovative Research Team Program (No. 2009010044), the China Postdoctoral Science Foundation (No. 2014M562233), the National Natural Science Foundation of Guangdong, China (No. 2015A030312011), and the Opened Fund of the State Key Laboratory on Integrated Optoelectronics (No. IOSKL2014KF17).

  6. 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 .

  7. 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.

  8. 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.

  9. Selective oxidation of the double bonds in the 4-phenyl-1,2,4-triazoline-3,5-dione diels-alder adduct of ergosterol acetate.

    PubMed

    Piatak, D M; Swenson, R P

    1984-01-01

    Methods for oxidations at the 6(7)- and 22(23)-double bonds in the phenyltriazoline adduct of ergosterol acetate (I) are described. KMnO4 and OsO4 were found to react with the 6(7)-double bond to yield the 6,7-glycol and osmate ester, respectively. Other reagents (I2/AgOAc, H2O2, m-chloroperbenzoic acid, HCO3H) formed either isomeric epoxides or glycols with the 22(23)-double bond, with the latter two reagents giving their products in quite high yields.

  10. 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.

  11. 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.

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

    PubMed

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

    2015-08-01

    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 MS(3) (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.

  13. 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

  14. Dirhodium carboxylates catalyzed enantioselective coupling reactions of α-diazophosphonates, anilines, and electron-deficient aldehydes.

    PubMed

    Zhou, Cong-Ying; Wang, Jing-Cui; Wei, Jinhu; Xu, Zhen-Jiang; Guo, Zhen; Low, Kam-Hung; Che, Chi-Ming

    2012-11-05

    Chiral dirhodium carboxylate complexes ([Rh(2)(S-PTAD)(4)] or [Rh(2)(S-PTTL)(4)]) efficiently catalyze asymmetric three-component coupling reactions of α-diazophosphonates, anilines, and electron-deficient aldehydes to give α-amino-β-hydroxyphosphonates. The high level of enantiocontrol provides evidence for the intermediacy of metal-bound ammonium ylide in the product-forming step.

  15. 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.

  16. Double bond localization in minor homoallylic fatty acid methyl esters using acetonitrile chemical ionization tandem mass spectrometry.

    PubMed

    Michaud, Anthony L; Diau, Guan-Yeu; Abril, Reuben; Brenna, J Thomas

    2002-08-15

    Double bond position in natural fatty acids is critical to biochemical properties, however, common instrument-based methods cannot locate double bonds in fatty acid methyl esters (FAME), the predominant analysis form of fatty acids. A recently described mass spectrometry (MS) method for locating double bonds in FAME is reported here for the analysis of minor (<1%) components of real FAME mixtures derived from three natural sources; golden algae (Schizochytrium sp.), primate brain white matter, and transgenic mouse liver. Acetonitrile chemical ionization tandem MS was used to determine double bond positions in 39 FAME, most at concentrations well below 1% of all fatty acid methyl esters. FAME identified in golden algae are 14:1n-6, 14:3n-3, 16:1n-7, 16:2n-6, 16:3n-6, 16:3n-3, 16:4n-3, 18:2n-7, 18:3n-7, 18:3n-8, 18:4n-3, 18:4n-5, 20:3n-7, 20:4n-3, 20:4n-5, 20:4n-7, 20:5n-3, and 22:4n-9. Additional FAME identified in primate brain white matter are 20:1n-7, 20:1n-9, 20:2n-7, 20:2n-9, 22:1n-7, 22:1n-9, 22:1n-13, 22:2n-6, 22:2n-7, 22:2n-9, 22:3n-6, 22:3n-7, 22:3n-9, 22:4n-6, 24:1n-7, 24:1n-9, and 24:4n-6. Additional FAME identified in mouse liver are 26:5n-6, 26:6n-3, 28:5n-6, and 28:6n-3. The primate brain 22:3n-7 and algae 18:4n-5 are novel fatty acids. These results demonstrate the usefulness of the technique for analysis of real samples. Tables are presented to aid in interpretation of acetonitrile CIMS/MS spectra.

  17. ELECTRON DONOR ACCEPTOR DESCRIPTORS OF THE SINGLE AND DOUBLE BONDED SUBSTITUENT AND HETEROATOM INCORPORATION EFFECTS. A REVIEW.

    PubMed

    Mazurek, Andrzej

    2016-01-01

    The properties of the series of Electron Donor-Acceptor (EDA) descriptors of classical substituent effect (sEDA(I), pEDA(I)), double bonded substituent effect (sEDA(=), pEDA(=)), heteroatom incorporation effect in monocyclic systems (sEDA(II), pEDA(II)), and in ring-junction position (sEDA(III), pEDA(III)), are reviewed. The descriptors show the amount of electrons donated to or withdrawn from the σ-(sEDA) or π(pEDA) valence orbitals by the substituent or incorporant. The new descriptors are expected to enrich the potency of QSAR analyses in drug design and materials chemistry.

  18. Car-Parrinello Molecular Dynamics Simulations of Infrared Spectra of Crystalline Vitamin C with Analysis of Double Minimum Proton Potentials for Medium-Strong Hydrogen Bonds.

    PubMed

    Brela, Mateusz Z; Wójcik, Marek J; Boczar, Marek; Witek, Łukasz; Yasuda, Mitsuru; Ozaki, Yukihiro

    2015-06-25

    We studied proton dynamics of a hydrogen bonds of the crystalline l-ascorbic acid. Our approach was based on the Car-Parrinello molecular dynamics. The focal point of our study was simulation of the infrared spectra of l-ascorbic acid associated with the O-H stretching modes that are very sensitive to the strength of hydrogen bonding. In the l-ascorbic acid there are four kinds of hydrogen bonds. We calculated their spectra by using anharmonic approximation and the time course of the dipole moment function as obtained from the Car-Parrinello simulation. The quantization of the nuclear motion of the protons was made to perform detailed analysis of strength and properties of hydrogen bonds. We presented double minimum proton potentials with small value of barriers for medium-strong hydrogen bonds. We have also shown the difference character of medium-strong hydrogen bonds compared to weaker hydrogen bonds in the l-ascorbic acid.

  19. 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.

  20. Double bond stereochemistry influences the susceptibility of short-chain isoprenoids and polyprenols to decomposition by thermo-oxidation.

    PubMed

    Molińska, Ewa; Klimczak, Urszula; Komaszyło, Joanna; Derewiaka, Dorota; Obiedziński, Mieczysław; Kania, Magdalena; Danikiewicz, Witold; Swiezewska, Ewa

    2015-04-01

    Isoprenoid alcohols are common constituents of living cells. They are usually assigned a role in the adaptation of the cell to environmental stimuli, and this process might give rise to their oxidation by reactive oxygen species. Moreover, cellular isoprenoids may also undergo various chemical modifications resulting from the physico-chemical treatment of the tissues, e.g., heating during food processing. Susceptibility of isoprenoid alcohols to heat treatment has not been studied in detail so far. In this study, isoprenoid alcohols differing in the number of isoprene units and geometry of the double bonds, β-citronellol, geraniol, nerol, farnesol, solanesol and Pren-9, were subjected to thermo-oxidation at 80 °C. Thermo-oxidation resulted in the decomposition of the tested short-chain isoprenoids as well as medium-chain polyprenols with simultaneous formation of oxidized derivatives, such as hydroperoxides, monoepoxides, diepoxides and aldehydes, and possible formation of oligomeric derivatives. Oxidation products were monitored by GC-FID, GC-MS, ESI-MS and spectrophotometric methods. Interestingly, nerol, a short-chain isoprenoid with a double bond in the cis (Z) configuration, was more oxidatively stable than its trans (E) isomer, geraniol. However, the opposite effect was observed for medium-chain polyprenols, since Pren-9 (di-trans-poly-cis-prenol) was more susceptible to thermo-oxidation than its all-trans isomer, solanesol. Taken together, these results experimentally confirm that both short- and long-chain polyisoprenoid alcohols are prone to thermo-oxidation.

  1. 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.

  2. 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

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

    PubMed

    Kilpatrick, Alexander F R; Green, Jennifer C; Cloke, F Geoffrey N

    2015-10-26

    The reactivity of the bis(pentalene)dititanium double-sandwich compound Ti2Pn(†)2 (1) (Pn(†) = 1,4-{Si(i)Pr3}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:η(2),η(2) 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 η(8) fashion to each of the formally Ti(III) 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-Ti(III) species to yield di-Ti(II) and di-Ti(IV) 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

  4. 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

  5. A density functional theory for association of fluid molecules with a functionalized surface: fluid-wall single and double bonding

    NASA Astrophysics Data System (ADS)

    Haghmoradi, Amin; Wang, Le; Chapman, Walter G.

    2017-02-01

    In this manuscript we extend Wertheim’s two-density formalism beyond its first order to model a system of fluid molecules with a single association site close to a planar hard wall with association sites on its surface in a density functional theory framework. The association sites of the fluid molecules are small enough that they can form only one bond, while the wall association sites are large enough to bond with more than one fluid molecule. The effects of temperature and of bulk fluid and wall site densities on the fluid density profile, extent of association, and competition between single and double bonding of fluid segments at the wall sites versus distance from the wall are presented. The theory predictions are compared with new Monte Carlo simulation results and they are in good agreement. The theory captures the surface coverage over wide ranges of temperature and bulk density by introducing the effect of steric hindrance in fluid association at a wall site.

  6. Electrostatic and Charge-Induced Methane Activation by a Concerted Double C-H Bond Insertion.

    PubMed

    Geng, Caiyun; Li, Jilai; Weiske, Thomas; Schlangen, Maria; Shaik, Sason; Schwarz, Helmut

    2017-02-01

    A mechanistically unique, simultaneous activation of two C-H bonds of methane has been identified during the course of its reaction with the cationic copper carbide, [Cu-C](+). Detailed high-level quantum chemical calculations support the experimental findings obtained in the highly diluted gas phase using FT-ICR mass spectrometry. The behavior of [Cu-C](+)/CH4 contrasts that of [Au-C](+)/CH4, for which a stepwise bond-activation scenario prevails. An explanation for the distinct mechanistic differences of the two coinage metal complexes is given. It is demonstrated that the coupling of [Cu-C](+) with methane to form ethylene and Cu(+) is modeled very well by the reaction of a carbon atom with methane mediated by an oriented external electric field of a positive point charge.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. Stability of Criegee intermediates formed by ozonolysis of different double bonds.

    PubMed

    Kalinowski, Jaroslaw; Heinonen, Petri; Kilpeläinen, Ilkka; Räsänen, Markku; Gerber, R Benny

    2015-03-19

    The formation of Criegee intermediates by ozonolysis of different species containing C═N and C═P bonds is studied computationally. Electronic structure calculations are carried out for the energetics of ozonolysis, and the lifetime of the Criegee intermediate formed is computed by transition state theory. All calculations are carried out for formation of CH2OO, the simplest Criegee intermediate. Extremely large differences are found for the lifetime of CH2OO depending on the specific C═N, C═P, and C═C precursor, due to the great variations in the exoergicity of the ozonolysis. The largest lifetimes of CH2OO are found to be up to a millisecond range for a Schiff base precursor, being orders of magnitude greater than for C═C and C═P precursors at the same conditions. The results provide insights into the role of the precursor in determining the stability of the Criegee species formed and suggest an approach for preparing Criegee intermediates of relatively long lifetimes.

  12. Copper-catalyzed double C-S bonds formation via different paths: synthesis of benzothiazoles from N-benzyl-2-iodoaniline and potassium sulfide.

    PubMed

    Zhang, Xiaoyun; Zeng, Weilan; Yang, Yuan; Huang, Hui; Liang, Yun

    2014-02-07

    A new, highly efficient procedure for the synthesis of benzothiazoles from easily available N-benzyl-2-iodoaniline and potassium sulfide has been developed. The results show copper-catalyzed double C-S bond formation via a traditional cross-coupling reaction and an oxidative cross-coupling reaction.

  13. 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.

  14. 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

  15. 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).

  16. 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.

  17. A novel vitamin D analog with two double bonds in its side chain. A potent inducer of osteoblastic cell differentiation.

    PubMed

    Mahonen, A; Jääskeläinen, T; Mäenpää, P H

    1996-04-12

    EB 1089 (1 alpha,25-dihydroxy-22,24-diene-24,26,27-trihomovitamin D3) is a novel, synthetic analog of calcitriol, characterized by two extra double bonds in its side chain. It is less potent than calcitriol in its calcemic action, but is an order of magnitude more potent in its antiproliferative action. The aim of this study was to determine the ability of EB 1089 to induce the well-known biological effects of calcitriol in MG-63 human osteosarcoma cells (i.e. by inhibiting cell proliferation and by induction of differentiation). Both calcitriol and EB 1089 significantly decreased cell growth after 2 days in culture. At 5 days, however, Eb 1089 was more potent than the natural hormone in inhibiting the proliferation of MG-63 cells. Potent effects of EB 1089 on cell differentiation were also seen in the stimulation of alkaline phosphatase activity, cellular vitamin D receptor mRNA levels, and medium osteocalcin synthesis. EB 1089 was clearly more effective than calcitriol in stimulating alkaline phosphatase activity and osteocalcin synthesis. In gel shift assays, the binding of vitamin D receptor to the composite AP-1 plus vitamin-D responsive promoter region of the human osteocalcin gene after EB 1089 treatment was stronger and longer-lasting than after calcitriol treatment.

  18. Novel Odd-Chain Fatty Acids with a Terminal Double Bond in Ovaries of the Limpet Cellana toreuma.

    PubMed

    Kawashima, Hideki; Ohnishi, Masao

    2017-04-01

    Our previous study characterized highly diverse dienoic fatty acids (FA), in particular an uncommon non-methylene-interrupted (NMI) FA, in the ovaries of the Japanese limpet Cellana toreuma belonging to the archaeogastropods, but many minor chemically unidentified FA remain. In this study, among previously unidentified FA (less than 0.1% of total FA), four novel NMI FA with a terminal double bond [7,18-nonadecadienoic (19:2Δ7,18), 11,18-nonadecadienoic (19:2Δ11,18), 7,20-heneicosadienoic (21:2Δ7,20), and 11,20-heneicosadienoic (21:2Δ11,20) acids] were found, along with known 14-pentadecenoic (15:1Δ14), 16-heptadecenoic (17:1Δ16), and 9,18-nonadecadienoic (19:2Δ9,18) acids, based on capillary GC-MS of their methyl esters, 3-pyridylcarbinol derivatives, and argentation thin-layer chromatography. From our findings, possible biosynthetic pathways for the novel FA are discussed.

  19. Aborted double bicycle-pedal isomerization with hydrogen bond breaking is the primary event of bacteriorhodopsin proton pumping.

    PubMed

    Altoè, Piero; Cembran, Alessandro; Olivucci, Massimo; Garavelli, Marco

    2010-11-23

    Quantum mechanics/molecular mechanics calculations based on ab initio multiconfigurational second order perturbation theory are employed to construct a computer model of Bacteriorhodopsin that reproduces the observed static and transient electronic spectra, the dipole moment changes, and the energy stored in the photocycle intermediate K. The computed reaction coordinate indicates that the isomerization of the retinal chromophore occurs via a complex motion accounting for three distinct regimes: (i) production of the excited state intermediate I, (ii) evolution of I toward a conical intersection between the excited state and the ground state, and (iii) formation of K. We show that, during stage ii, a space-saving mechanism dominated by an asynchronous double bicycle-pedal deformation of the C10═C11─C12═C13─C14═N moiety of the chromophore dominates the isomerization. On this same stage a N─H/water hydrogen bond is weakened and initiates a breaking process that is completed during stage iii.

  20. 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.

  1. Rationally designed calix[4]arene-pyrrolotetrathiafulvalene receptors for electron-deficient neutral guests.

    PubMed

    Düker, Matthias H; Schäfer, Hannes; Zeller, Matthias; Azov, Vladimir A

    2013-05-17

    Four upper rim bis-monopyrrolotetrathiafulvalene-calix[4]arene conjugates 2a,b and 3a,b have been efficiently synthesized using a modular construction approach. The new compounds feature a molecular tweezer architecture with a quasi-parallel arrangement of redox-active tetrathiafulvalene (TTF) arms, which serve as the guest binding centers. Complexation studies using UV/vis binding titrations revealed a high affinity of the calixarene-TTF receptors for planar electron-deficient guests, leading to formation of deeply colored charge-transfer complexes in solution. The binding efficiency of the receptors depends on the flexibility of the calixarene scaffolds and the electronic nature of the TTF arms: the highest binding efficiency is shown by receptor 2b, featuring a highly preorganized molecular structure and an electron-rich TTF moiety.

  2. 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

  3. Latex Clearing Protein—an Oxygenase Cleaving Poly(cis-1,4-Isoprene) Rubber at the cis Double Bonds

    PubMed Central

    Hiessl, Sebastian; Böse, Dietrich; Oetermann, Sylvia; Eggers, Jessica; Pietruszka, Jörg

    2014-01-01

    Gordonia polyisoprenivorans strain VH2, a potent rubber-degrading actinomycete, harbors two latex clearing proteins (Lcps), which are known to be essential for the microbial degradation of rubber. However, biochemical information on the exact role of this protein in the degradation of polyisoprene was lacking. In this study, the gene encoding Lcp1VH2 was heterologously expressed in strains of Escherichia coli, the corresponding protein was purified, and its role in rubber degradation was examined by measurement of oxygen consumption as well as by chromatographic and spectroscopic methods. It turned out that active Lcp1VH2 is a monomer and is responsible for the oxidative cleavage of poly(cis-1,4-isoprene) in synthetic as well as in natural rubber by the addition of oxygen (O2) to the cis double bonds. The resulting oligomers possess repetitive isoprene units with aldehyde (CHO-CH2—) and ketone (—CH2-CO-CH3) functional groups at the termini. Two fractions with average isoprene contents of 18 and 10, respectively, were isolated, thus indicating an endocleavage mechanism. The activity of Lcp1VH2 was determined by applying a polarographic assay. Alkenes, acyclic terpenes, or other rubber-like polymers, such as poly(cis-1,4-butadiene) or poly(trans-1,4-isoprene), are not oxidatively cleaved by Lcp1VH2. The pH and temperature optima of the enzyme are at pH 7 and 30°C, respectively. Furthermore, it was demonstrated that active Lcp1VH2 is a Cu(II)-containing oxygenase that exhibits a conserved domain of unknown function which cannot be detected in any other hitherto-characterized enzyme. The results presented here indicate that this domain might represent a new protein family of oxygenases. PMID:24928880

  4. Latex clearing protein-an oxygenase cleaving poly(cis-1,4-isoprene) rubber at the cis double bonds.

    PubMed

    Hiessl, Sebastian; Böse, Dietrich; Oetermann, Sylvia; Eggers, Jessica; Pietruszka, Jörg; Steinbüchel, Alexander

    2014-09-01

    Gordonia polyisoprenivorans strain VH2, a potent rubber-degrading actinomycete, harbors two latex clearing proteins (Lcps), which are known to be essential for the microbial degradation of rubber. However, biochemical information on the exact role of this protein in the degradation of polyisoprene was lacking. In this study, the gene encoding Lcp1VH2 was heterologously expressed in strains of Escherichia coli, the corresponding protein was purified, and its role in rubber degradation was examined by measurement of oxygen consumption as well as by chromatographic and spectroscopic methods. It turned out that active Lcp1VH2 is a monomer and is responsible for the oxidative cleavage of poly(cis-1,4-isoprene) in synthetic as well as in natural rubber by the addition of oxygen (O2) to the cis double bonds. The resulting oligomers possess repetitive isoprene units with aldehyde (CHO-CH2-) and ketone (-CH2-CO-CH3) functional groups at the termini. Two fractions with average isoprene contents of 18 and 10, respectively, were isolated, thus indicating an endocleavage mechanism. The activity of Lcp1VH2 was determined by applying a polarographic assay. Alkenes, acyclic terpenes, or other rubber-like polymers, such as poly(cis-1,4-butadiene) or poly(trans-1,4-isoprene), are not oxidatively cleaved by Lcp1VH2. The pH and temperature optima of the enzyme are at pH 7 and 30°C, respectively. Furthermore, it was demonstrated that active Lcp1VH2 is a Cu(II)-containing oxygenase that exhibits a conserved domain of unknown function which cannot be detected in any other hitherto-characterized enzyme. The results presented here indicate that this domain might represent a new protein family of oxygenases.

  5. 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.

  6. Q-Band Electron-Nuclear Double Resonance Reveals Out-of-Plane Hydrogen Bonds Stabilize an Anionic Ubisemiquinone in Cytochrome bo3 from Escherichia coli.

    PubMed

    Sun, Chang; Taguchi, Alexander T; Vermaas, Josh V; Beal, Nathan J; O'Malley, Patrick J; Tajkhorshid, Emad; Gennis, Robert B; Dikanov, Sergei A

    2016-10-11

    The respiratory cytochrome bo3 ubiquinol oxidase from Escherichia coli has a high-affinity ubiquinone binding site that stabilizes the one-electron reduced ubisemiquinone (SQH), which is a transient intermediate during the electron-mediated reduction of O2 to water. It is known that SQH is stabilized by two strong hydrogen bonds from R71 and D75 to ubiquinone carbonyl oxygen O1 and weak hydrogen bonds from H98 and Q101 to O4. In this work, SQH was investigated with orientation-selective Q-band (∼34 GHz) pulsed (1)H electron-nuclear double resonance (ENDOR) spectroscopy on fully deuterated cytochrome (cyt) bo3 in a H2O solvent so that only exchangeable protons contribute to the observed ENDOR spectra. Simulations of the experimental ENDOR spectra provided the principal values and directions of the hyperfine (hfi) tensors for the two strongly coupled H-bond protons (H1 and H2). For H1, the largest principal component of the proton anisotropic hfi tensor Tz' = 11.8 MHz, whereas for H2, Tz' = 8.6 MHz. Remarkably, the data show that the direction of the H1 H-bond is nearly perpendicular to the quinone plane (∼70° out of plane). The orientation of the second strong hydrogen bond, H2, is out of plane by ∼25°. Equilibrium molecular dynamics simulations on a membrane-embedded model of the cyt bo3 QH site show that these H-bond orientations are plausible but do not distinguish which H-bond, from R71 or D75, is nearly perpendicular to the quinone ring. Density functional theory calculations support the idea that the distances and geometries of the H-bonds to the ubiquinone carbonyl oxygens, along with the measured proton anisotropic hfi couplings, are most compatible with an anionic (deprotonated) ubisemiquinone.

  7. Synthesis of 2-aminoindolizines by 1,3-dipolar cycloaddition of pyridinium ylides with electron-deficient ynamides.

    PubMed

    Brioche, Julien; Meyer, Christophe; Cossy, Janine

    2015-06-05

    Electron-deficient ynamides, possessing an ynoate or an ynone moiety, have been successfully involved for the first time in a 1,3-dipolar cycloaddition with stabilized pyridinium ylides. These reactions afford an efficient and general access toward a variety of substituted 2-aminoindolizines which can serve as useful precursors for the synthesis of other more complex nitrogen heterocycles.

  8. Lewis base catalyzed [4+2] annulation of electron-deficient chromone-derived heterodienes and acetylenes.

    PubMed

    Dückert, Heiko; Khedkar, Vivek; Waldmann, Herbert; Kumar, Kamal

    2011-04-26

    Lewis base catalyzed [4+2] annulation reactions between electron-deficient chromone oxa- and azadienes and acetylene carboxylates provide tricyclic benzopyrones inspired by natural products. An asymmetric synthesis of the tricyclic benzopyrones was developed by using modified cinchona alkaloids as enantiodifferentiating Lewis base catalysts.

  9. Biotransformation of the double bond in allyl glycidyl ether to an epoxide ring. Evidence from hemoglobin adducts in mice.

    PubMed

    Pérez, H L; Osterman-Golkar, S

    2000-02-15

    Allyl glycidyl ether (AGE) is used industrially in the production of various epoxy resins. The compound is mutagenic and evidence for carcinogenicity in mice and rats has been reported. A previous study in mice showed that AGE reacts directly, without metabolic activation, with N-terminal valine in hemoglobin to form adducts (AGEVal). Metabolism of AGE may lead to formation of diglycidyl ether (I) through epoxidation of the double bond or 1-allyloxy-2,3-dihydroxypropane (II) through hydrolysis of the epoxide ring. 2,3-Dihydroxypropyl glycidyl ether (III) may be formed either by hydrolysis of I or epoxidation of II. The main aim of the present study was to investigate if AGE is metabolized to the reactive epoxides I or III by analysis of adducts with hemoglobin. Nine male mice (C3H/Hej) were administered AGE dissolved in tricaprylin, 4 mg/mouse, by intraperitoneal (i.p.) injection. Eleven male mice were administered 4 mg/mouse of AGE dissolved in acetone, by skin application. Adducts of I or III with N-terminal valine, N-(2-hydroxy-3-(2,3-dihydroxy)propyloxy)propylvaline (diOHPrGEVal), were demonstrated in mice administered AGE by i.p. injection. The levels were in the range 1600-5600 pmol/g globin. The level of diOHPrGEVal in mice administered AGE by skin application (n = 5) was below the detection limit of the analytical method, 20 pmol/g globin. The level of AGEVal, analyzed in mice administered AGE by skin application (n = 6), was about 20 pmol/g globin (median value), as compared with 1600 pmol/g globin previously found in mice administered AGE by i.p. injection. Neither AGEVal nor diOHPrGEVal were detected in control animals. Both adducts were analyzed using a modified Edman method for derivatization and using gas chromatography/tandem mass spectrometry for detection. The hydroxyl groups of the Edman derivative of diOHPrGEVal were protected by acetylation.

  10. Energetics of tert-butoxyl addition reaction to norbornadiene: a method for estimating the pi-bond strength of a carbon-carbon double bond.

    PubMed

    Nunes, Paulo M; Estácio, Sílvia G; Lopes, Gustavo T; Agapito, Filipe; Santos, Rui C; Costa Cabral, Benedito J; Borges dos Santos, Rui M; Martinho Simões, José A

    2009-06-11

    The energetics of tert-butoxyl radical addition reaction to norbornadiene was investigated by time-resolved photoacoustic calorimetry (TR-PAC). The result, together with the C-O bond dissociation enthalpy (BDE) in the addition product, allowed us to calculate the pi-bond dissociation enthalpy in norbornadiene. Quantum chemistry (QC) methods were also used to obtain several enthalpies of reaction of the addition of oxygen-centered radicals to alkenes. The pi-bond dissociation enthalpies in these molecules were calculated by a procedure similar to that used in the case of norbornadiene and were compared with the pi-BDE values obtained by the method proposed by Benson. These two different approaches yield similar values for the pi-BDEs in alkenes, indicating that the addition method proposed in the present study is a valid way to derive that quantity. The influence of strain in the pi-BDEs of cyclic alkenes was investigated and allowed us to justify the difference between the pi-BDE in norbornene and norbornadiene. Finally, the thermochemistry of the addition and abstraction reactions involving these two molecules and tert-butoxyl radical was analyzed.

  11. Study of double bond equivalents and the numbers of carbon and oxygen atom distribution of dissolved organic matter with negative-mode FT-ICR MS.

    PubMed

    Bae, EunJung; Yeo, In Joon; Jeong, Byungkwan; Shin, Yongsik; Shin, Kyung-Hoon; Kim, Sunghwan

    2011-06-01

    A strong linear relationship was observed between the average double bond equivalence (DBE) and the ratio of carbon to oxygen atoms in oxygenated compounds of dissolved organic matter (DOM). Data were acquired by a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS), equipped with a negative-mode electrospray ionization source. The slope and y-intercepts extracted from the linear relationship can be used to compare DOM samples originating from different locations. Significant differences in these parameters were observed between inland riverine and offshore coastal DOM samples. Offshore coastal DOM molecules underwent a change of one DBE for each removal or addition of two oxygen atoms. This suggested the existence of multiple carboxyl groups, each of which contains a double bond and two oxygen atoms. Inland riverine samples exhibited a change of ~1.5 DBE following the addition or removal of two oxygen atoms. This extra change in DBE was attributed to cyclic structures or unsaturated chemical bonds. The DBE value with maximum relative abundance and the minimum DBE value for each class of oxygenated compounds showed that approximately two oxygen atoms contributed to a unity change in DBE. The qualitative analyses given here are in a good agreement with results obtained from analyses using orthogonal analytical techniques. This study demonstrates that DBE and the carbon number distribution, observed by high resolution mass spectrometry, can be valuable in elucidating and comparing structural features of oxygenated molecules of DOM.

  12. Pd-Catalyzed Autotandem Reactions with N-Tosylhydrazones. Synthesis of Condensed Carbo- and Heterocycles by Formation of a C-C Single Bond and a C═C Double Bond on the Same Carbon Atom.

    PubMed

    Paraja, Miguel; Valdés, Carlos

    2017-04-05

    A new Pd-catalyzed autotandem reaction is introduced that consists of the cross-coupling of a benzyl bromide with a N-tosylhydrazone followed by an intramolecular Heck reaction with an aryl bromide. During the process, a single and a double C-C bond are formed on the same carbon atom. Two different arrangements for the reactive functional groups are possible, rendering great flexibility to the transformation. The same strategy led to 9-methylene-9H-fluorenes, 9-methylene-9H-xanthenes, 9-methylene-9,10-dihydroacridines, and also dihydropyrroloisoquinoline and dihydroindoloisoquinoline derivatives.

  13. Reduction of electron deficient guanine radical species in plasmid DNA by tyrosine derivatives.

    PubMed

    Tsoi, Mandi; Do, Trinh T; Tang, Vicky J; Aguilera, Joseph A; Milligan, Jamie R

    2010-06-07

    Guanine bases are the most easily oxidized sites in DNA and therefore electron deficient guanine radical species are major intermediates in the direct effect of ionizing radiation (ionization of the DNA itself) on DNA as a consequence of hole migration to guanine. As a model for this process we have used gamma-irradiation in the presence of thiocyanate ions to generate single electron oxidized guanine radicals in a plasmid target in aqueous solution. The stable species formed from these radicals can be detected and quantified by the formation of strand breaks in the plasmid after a post-irradiation incubation using a suitable enzyme. If a tyrosine derivative is also present during irradiation, the production of guanine oxidation products is decreased by electron transfer from tyrosine to the intermediate guanyl radical species. By using cationic tyrosine containing ligands we are able to observe this process when the tyrosine is electrostatically bound to the plasmid. The driving force dependence of this reaction was determined by comparing the reactivity of tyrosine with its 3-nitro analog. The results imply that the electron transfer reaction is coupled to a proton transfer. The experimental conditions used in this model system provide a reasonable approximation to those involved in the radioprotection of DNA by tightly bound proteins in chromatin.

  14. Platinum-based organometallic folders for the recognition of electron deficient aromatic substrates.

    PubMed

    Peris, Eduardo Victor; Nuevo, Daniel; Gonell, Sergio; Poyatos, Macarena

    2017-04-12

    A series of platinum complexes with cis-oriented polyaromatic N-heterocyclic carbene ligands were prepared and characterized. The relative disposition of the polyaromatic ligands about the metal make these compounds to behave as a metallofolder, with a pocket defined by the void space between the polyaromatic functionalities. The complexes were used as receptors of organic molecules, where they showed selective affinity for binding electron-deficient aromatic substrates, such as 1,2,4,5-tetracyanobenzene (TCNB), 2,4,7-trinitro-9-fluorenone (NTFLU) and 1,4,5,8-naphtalenetetracarboxylic dianhydride (NTCDA). The binding affinities of two of the metallofolders with these substrates were determined by means of 1H NMR titrations. Electrospay mass spectrometry (ESI-MS) was also used to assess the affinities. The molecular structure of one of the platinum folders was determined in the presence of TCNB, showing the clear interaction between this guest molecule and the folder formed by the two mutually cis polyaromatic ligands. This work demonstrates how the presence of the mutually cis polyaromatic ligands may constitute a very useful tool for the preparation of metal-based receptors.

  15. Theoretical study of activation C sbnd C double bond of C 2H 4 by CrO2+ in gas phase

    NASA Astrophysics Data System (ADS)

    Wang, Yong-Cheng; Chen, Xiao-Xia

    2006-05-01

    The gas-phase reaction of activation C sbnd C double bond of C 2H 4 by CrO2+(2A1/4A″) has been investigated using density functional theory (DFT) at the UB3LYP/6-311++G (3df, 3pd)//6-311G(2d, p) level. The calculation results show that the reaction experiences a rearranged process. On the basis of Hammond postulate, this is a typical 'two-state reactivity' (TSR) reaction. The involving crossing between the potential energy surfaces is discussed by means of the intrinsic reaction coordinate (IRC) approach used by Yoshizawa et al., and a crossing point (CP) is located. In addition, the orbital interaction analysis of activation C sbnd C bond is carried out by fragment molecular orbital (FMO), and compared with the DCD model.

  16. Collision-induced dissociation of fatty acid [M - 2H + Na]- ions: charge-directed fragmentation and assignment of double bond position.

    PubMed

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

    2014-11-01

    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: ∆(9,12,15)18:3, ∆(6,9,12)18:3, and ∆(5,8,11)18:3. 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.

  17. The role of the trans double bond in skin barrier sphingolipids: permeability and infrared spectroscopic study of model ceramide and dihydroceramide membranes.

    PubMed

    Skolová, Barbora; Jandovská, Kateřina; Pullmannová, Petra; Tesař, Ondřej; Roh, Jaroslav; Hrabálek, Alexandr; Vávrová, Kateřina

    2014-05-20

    Dihydroceramides (dCer) are members of the sphingolipid family that lack the C4 trans double bond in their sphingoid backbone. In addition to being precursors of ceramides (Cer) and phytoceramides, dCer have also been found in the extracellular lipid membranes of the epidermal barrier, the stratum corneum. However, their role in barrier homeostasis is not known. We studied how the lack of the trans double bond in dCer compared to Cer influences the permeability, lipid chain order, and packing of multilamellar membranes composed of the major skin barrier lipids: (d)Cer, fatty acids, cholesterol, and cholesteryl sulfate. The permeability of the membranes with long-chain dCer was measured using various markers and was either comparable to or only slightly greater than (by up to 35%, not significant) that of the Cer membranes. The dCer were less sensitive to acyl chain shortening than Cer (the short dCer membranes were up to 6-fold less permeable that the corresponding short Cer membranes). Infrared spectroscopy showed that long dCer mixed less with fatty acids but formed more thermally stable ordered domains than Cer. The key parameter explaining the differences in permeability in the short dCer and Cer was the proportion of the orthorhombic phase. Our results suggest that the presence of the trans double bond in Cer is not crucial for the permeability of skin lipid membranes and that dCer may be underappreciated members of the stratum corneum lipid barrier that increase its heterogeneity.

  18. 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.

  19. Resolution of concerted versus sequential mechanisms in photo-induced double-proton transfer reaction in 7-azaindole H-bonded dimer

    PubMed Central

    Catalán, Javier; del Valle, Juan Carlos; Kasha, Michael

    1999-01-01

    The experimental and theoretical bases for a synchronous or concerted double-proton transfer in centro-symmetric H-bonded electronically excited molecular dimers are presented. The prototype model is the 7-azaindole dimer. New research offers confirmation of a concerted mechanism for excited-state biprotonic transfer. Recent femtosecond photoionization and coulombic explosion techniques have given rise to time-of-flight MS observations suggesting sequential two-step biprotonic transfer for the same dimer. We interpret the overall species observed in the time-of-flight experiments as explicable without conflict with the concerted mechanism of proton transfer. PMID:10411876

  20. Selective reduction of C=C double bonds in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of microcystins.

    PubMed

    Deleuze, Christelle; De Pauw, Edwin; Quinton, Loic

    2010-01-01

    Cyanobacteria are photosynthetic bacteria encountered in various aquatic environments. Some of them are able to produce powerful toxins called cyanotoxins. Among cyanotoxins, microcystins (MCs) constitute a group of closely related cyclic heptapeptides. Their sequences are made up of classical amino acids as well as post- translational modified ones. Interestingly, in vivo metabolism of microcystins seems to be greatly dependent on various minor structural differences and particularly those of the seventh amino acid, which can be either dehydroalanine (or a derivative), dehydroaminobutyric acid (or a derivative), serine or alanine. As a consequence, microcystins have been classified on the basis of the nature of this singular amino acid. A major difficulty in the classification of such toxins is that some of them share the same molecular masses and the same molecular formulas. Consequently, a simple mass measurement is not sufficient to determine the structure and the class of a toxin of interest. Heavy and expensive techniques are used to classify them, such as multi-dimensional nuclear magnetic resonance and amino acid analysis. In this work, a new matrix-assisted laser desorption/ionization time-of-flight method leading to an easy classification of MCs is proposed. The methodology relies on the reductive properties of the matrix 1,5-diaminonaphtalene (1,5-DAN) which appears to be able to selectively reduce the double carbon-carbon bond belonging to the seventh amino acid. Moreover, the yield of reduction seems to be influenced by the degree of substitution of this double bond, allowing a discrimination between dehydroalanine and dehydroaminobutyric acid. This selective reduction was confirmed by the study of three synthetic peptides by mass spectrometry and tandem mass spectrometry. According to these results, the use of reductive matrices seems to be promising in the study of microcystins and in their classification. More generally, 1,5-DAN allows the selective

  1. 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.

  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.

  3. Bis(alkyl) rare-earth complexes coordinated by bulky tridentate amidinate ligands bearing pendant Ph2P[double bond, length as m-dash]O and Ph2P[double bond, length as m-dash]NR groups. Synthesis, structures and catalytic activity in stereospecific isoprene polymerization.

    PubMed

    Rad'kova, Natalia Yu; Tolpygin, Aleksei O; Rad'kov, Vasily Yu; Khamaletdinova, Nadia M; Cherkasov, Anton V; Fukin, Georgi K; Trifonov, Alexander A

    2016-11-22

    A series of new tridentate amidines 2-[Ph2P[double bond, length as m-dash]X]C6H4NHC(tBu)[double bond, length as m-dash]N(2,6-R2C6H3) (X = O, R = iPr (1); X = S, R = Me (2); X = NPh, R = Me (3); X = N(2,6-Me2C6H3), R = Me (4)) bearing various types of donor Ph2P[double bond, length as m-dash]X groups in a pendant chain was synthesized. Bis(alkyl) complexes {2-[Ph2P[double bond, length as m-dash]X]C6H4NC(tBu)N(2,6-R2C6H3)}Ln(CH2SiMe3)2 (Ln = Y, X = O, R = iPr (5); Ln = Er, X = O, R = iPr (6); Ln = Lu, X = O, R = iPr (7); Ln = Y, X = NPh, R = Me (8); Ln = Lu, X = NPh, R = Me (9); Ln = Lu, X = N(2,6-Me2C6H3), R = Me (10)) were prepared using alkane elimination reactions of 1, 3 and 4 with Ln(CH2SiMe3)3(THF)2 (Ln = Y, Er, Lu) in toluene and were isolated in 45 (5), 62 (6), 56 (7), 65 (8), 60 (9), and 60 (10) % yields respectively. The X-ray diffraction studies showed that complexes 6-8 are solvent free and feature intramolecular coordination of the P[double bond, length as m-dash]X (X = O, NPh) group to the lanthanide ions. The ternary systems 5-10/borate/AlR3 (borate = [PhNHMe2][B(C6F5)4], [Ph3C][B(C6F5)4], AlR3 = AliBu3, AliBu2H; molar ratio = 1/1/10 or 1/1/1, toluene) proved to be active in isoprene polymerization and enable complete conversion of 1000-10 000 equivalents of the monomer into a polymer at 25 °C within 0.5-24 h affording polyisoprenes with polydispersities Mw/Mn = 1.22-3.18. A comparative study of the catalytic performance of the bis(alkyl) complexes coordinated by tridentate amidinate ligands containing different pendant donor groups demonstrated that replacement of the Ph2P[double bond, length as m-dash]O group by Ph2P[double bond, length as m-dash]NPh leads to a switch of stereoselectivity in isoprene polymerization from cis-1,4 (up to 98.5%) to trans-1,4 (up to 84.8%). And conversely introduction of methyl substituents in the 2,6 positions of the phenyl group of the Ph2P[double bond, length as m-dash]NPh fragment allows us to restore the 1,4-cis

  4. Dynamic 1H-NMR study of unusually high barrier to rotation about the partial Csbnd N double bond in N,N-dimethyl carbamoyl 5-aryloxytetrazoles

    NASA Astrophysics Data System (ADS)

    Movahedifar, Fahimeh; Modarresi-Alam, Ali Reza; Kleinpeter, Erich; Schilde, Uwe

    2017-04-01

    The synthesis of new N,N-dimethyl carbamoyl 5-aryloxytetrazoles have been reported. Their dynamic 1H-NMR via rotation about Csbnd N bonds in moiety of urea group [a; CO-NMe2 and b; (2-tetrazolyl)N-CO rotations] in the solvents CDCl3 (223-333 K) and DMSO (298-363 K) is studied. Accordingly, the free energies of activation, obtained 16.5 and 16.9 kcal mol-1 respectively, attributed to the conformational isomerization about the Me2Nsbnd Cdbnd O bond (a rotation). Moreover, a and b barrier to rotations in 5-((4-methylphenoxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide (P) also were computed at level of B3LYP using 6-311++G** basis set. The optimized geometry parameters are in good agreement with X-ray structure data. The computation of energy barrier for a and b was determined 16.9 and 2.5 kcal mol-1, respectively. The former is completely in agreement with the result obtained via dynamic NMR. X-ray structure analysis data demonstrate that just 2-acylated tetrazole was formed in the case of 5-(p-tolyloxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide. X-ray data also revealed a planar trigonal orientation of the Me2N group which is coplanar to carbonyl group with the partial double-bond Csbnd N character. It also demonstrates the synperiplanar position of Cdbnd O group with tetrazolyl ring. On average, in solution the plane containing carbonyl bond is almost perpendicular to the plane of the tetrazolyl ring (because of steric effects as confirmed by B3LYP/6-311++G**) while the plane containing Me2N group is coplanar with carbonyl bond which is in contrast with similar urea derivatives and it demonstrates the unusually high rotational energy barrier of these compounds.

  5. An electron-deficient small molecule accessible from sustainable synthesis and building blocks for use as a fullerene alternative in organic photovoltaics.

    PubMed

    McAfee, Seth M; Topple, Jessica M; Payne, Abby-Jo; Sun, Jon-Paul; Hill, Ian G; Welch, Gregory C

    2015-04-27

    An electron-deficient small molecule accessible from sustainable isoindigo and phthalimide building blocks was synthesized via optimized synthetic procedures that incorporate microwave-assisted synthesis and a heterogeneous catalyst for Suzuki coupling, and direct heteroarylation carbon-carbon bond forming reactions. The material was designed as a non-fullerene acceptor with the help of DFT calculations and characterized by optical, electronic, and thermal analysis. Further investigation of the material revealed a differing solid-state morphology with the use of three well-known processing conditions: thermal annealing, solvent vapor annealing and small volume fractions of 1,8-diiodooctane (DIO) additive. These unique morphologies persist in the active layer blends and have demonstrated a distinct influence on device performance. Organic photovoltaic-bulk heterojunction (OPV-BHJ) devices show an inherently high open circuit voltage (Voc ) with the best power conversion efficiency (PCE) cells reaching 1.0 V with 0.4 v/v % DIO as a processing additive.

  6. 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

    2016-03-02

    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.

  7. Differential roles of internal and terminal double bonds in docosahexaenoic acid: Comparative study of cytotoxicity of polyunsaturated fatty acids to HT-29 human colorectal tumor cell line.

    PubMed

    Sato, Satoshi B; Sato, Sho; Kawamoto, Jun; Kurihara, Tatsuo

    2011-01-01

    The role of the double bonds in docosahexaenoic acid (22:6(Δ4,7,10,13,16,19); DHA) in cytotoxic lipid peroxidation was studied in a superoxide dismutase-defective human colorectal tumor cell line, HT-29. In a conventional culture, DHA and other polyunsaturated fatty acids (PUFAs) were found to induce acute lipid peroxidation and subsequent cell death. PUFAs that lack one or both the terminal double bonds (Δ19 and Δ4) but share Δ7,10,13,16 such as 22:5(Δ7,10,13,16,19), 22:5(Δ4,7,10,13,16), and 22:4(Δ7,10,13,16) were more effective than DHA. Lipid peroxidation and cell death were completely inhibited, except by 22:4(Δ7,10,13,16) when radical-mediated reactions were suppressed by culturing cells in 2% O(2) in the presence of vitamin E. DHA and C22:5 PUFAs but not 22:4(Δ7,10,13,16) were efficiently incorporated in phosphatidylinositol, regardless of the culturing conditions. These and other results suggested that the internal unsaturations Δ7,10,13,16 were sensitive to lipid peroxidation, whereas the terminal ones Δ19 and Δ4 appeared to be involved in assimilation into phospholipids.

  8. Unveiling of novel regio-selective fatty acid double bond hydratases from Lactobacillus acidophilus involved in the selective oxyfunctionalization of mono- and di-hydroxy fatty acids.

    PubMed

    Kim, Kyoung-Rok; Oh, Hye-Jin; Park, Chul-Soon; Hong, Seung-Hye; Park, Ji-Young; Oh, Deok-Kun

    2015-11-01

    The aim of this study is the first time demonstration of cis-12 regio-selective linoleate double-bond hydratase. Hydroxylation of fatty acids, abundant feedstock in nature, is an emerging alternative route for many petroleum replaceable products thorough hydroxy fatty acids, carboxylic acids, and lactones. However, chemical route for selective hydroxylation is still quite challenging owing to low selectivity and many environmental concerns. Hydroxylation of fatty acids by hydroxy fatty acid forming enzymes is an important route for selective biocatalytic oxyfunctionalization of fatty acids. Therefore, novel fatty acid hydroxylation enzymes should be discovered. The two hydratase genes of Lactobacillus acidophilus were identified by genomic analysis, and the expressed two recombinant hydratases were identified as cis-9 and cis-12 double-bond selective linoleate hydratases by in vitro functional validation, including the identification of products and the determination of regio-selectivity, substrate specificity, and kinetic parameters. The two different linoleate hydratases were the involved enzymes in the 10,13-dihydroxyoctadecanoic acid biosynthesis. Linoleate 13-hydratase (LHT-13) selectively converted 10 mM linoleic acid to 13S-hydroxy-9(Z)-octadecenoic acid with high titer (8.1 mM) and yield (81%). Our study will expand knowledge for microbial fatty acid-hydroxylation enzymes and facilitate the designed production of the regio-selective hydroxy fatty acids for useful chemicals from polyunsaturated fatty acid feedstocks.

  9. 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

  10. Determination of the hydrocarbon core structure of fluid dioleoylphosphocholine (DOPC) bilayers by x-ray diffraction using specific bromination of the double-bonds: effect of hydration.

    PubMed Central

    Hristova, K; White, S H

    1998-01-01

    Changes in the structure of the hydrocarbon core (HC) of fluid lipid bilayers can reveal how bilayers respond to the partitioning of peptides and other solutes (Jacobs, R. E., and S. H. White. 1989. Biochemistry. 28:3421-3437). The structure of the HC of dioleoylphosphocholine (DOPC) bilayers can be determined from the transbilayer distribution of the double-bonds (Wiener, M. C., and S. H. White. 1992. Biophys. J. 61:434-447). This distribution, representing the time-averaged projection of the double-bond positions onto the bilayer normal (z), can be obtained by means of neutron diffraction and double-bond specific deuteration (Wiener, M. C., G. I. King, and S. H. White. 1991. Biophys. J. 60:568-576). For fully resolved bilayer profiles, a close approximation of the distribution could be obtained by x-ray diffraction and isomorphous bromine labeling at the double-bonds of the DOPC sn-2 acyl chain (Wiener, M. C., and S. H. White. 1991. Biochemistry. 30:6997-7008). We have modified the bromine-labeling approach in a manner that permits determination of the distribution in under-resolved bilayer profiles observed at high water contents. We used this new method to determine the transbilayer distribution of the double-bond bromine labels of DOPC over a hydration range of 5.4 to 16 waters per lipid, which reveals how the HC structure changes with hydration. We found that the transbilayer distributions of the bromines can be described by a pair of Gaussians of 1/e half-width A(Br) located at z = +Z(Br) relative to the bilayer center. For hydrations from 5.4 waters up to 9.4 waters per lipid, Z(Br) decreases from 7.97 +/- 0.27 A to 6.59 +/- 0.15 A, while A(Br) increased from 4.62 +/- 0.62 A to 5.92 +/- 0.37 A, consistent with the expected hydration-induced decrease in HC thickness and increase in area per lipid. After the phosphocholine hydration shell was filled at approximately 12 waters per lipid, we observed a shift in Z(Br) to approximately 7.3 A, indicative of a

  11. Determination of the hydrocarbon core structure of fluid dioleoylphosphocholine (DOPC) bilayers by x-ray diffraction using specific bromination of the double-bonds: effect of hydration.

    PubMed

    Hristova, K; White, S H

    1998-05-01

    Changes in the structure of the hydrocarbon core (HC) of fluid lipid bilayers can reveal how bilayers respond to the partitioning of peptides and other solutes (Jacobs, R. E., and S. H. White. 1989. Biochemistry. 28:3421-3437). The structure of the HC of dioleoylphosphocholine (DOPC) bilayers can be determined from the transbilayer distribution of the double-bonds (Wiener, M. C., and S. H. White. 1992. Biophys. J. 61:434-447). This distribution, representing the time-averaged projection of the double-bond positions onto the bilayer normal (z), can be obtained by means of neutron diffraction and double-bond specific deuteration (Wiener, M. C., G. I. King, and S. H. White. 1991. Biophys. J. 60:568-576). For fully resolved bilayer profiles, a close approximation of the distribution could be obtained by x-ray diffraction and isomorphous bromine labeling at the double-bonds of the DOPC sn-2 acyl chain (Wiener, M. C., and S. H. White. 1991. Biochemistry. 30:6997-7008). We have modified the bromine-labeling approach in a manner that permits determination of the distribution in under-resolved bilayer profiles observed at high water contents. We used this new method to determine the transbilayer distribution of the double-bond bromine labels of DOPC over a hydration range of 5.4 to 16 waters per lipid, which reveals how the HC structure changes with hydration. We found that the transbilayer distributions of the bromines can be described by a pair of Gaussians of 1/e half-width A(Br) located at z = +Z(Br) relative to the bilayer center. For hydrations from 5.4 waters up to 9.4 waters per lipid, Z(Br) decreases from 7.97 +/- 0.27 A to 6.59 +/- 0.15 A, while A(Br) increased from 4.62 +/- 0.62 A to 5.92 +/- 0.37 A, consistent with the expected hydration-induced decrease in HC thickness and increase in area per lipid. After the phosphocholine hydration shell was filled at approximately 12 waters per lipid, we observed a shift in Z(Br) to approximately 7.3 A, indicative of a

  12. 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.

  13. [The titration of double bonds in fatty acids of blood plasma in patients in testing of glucose tolerance].

    PubMed

    Titov, V N; Sazhina, N N; Evteeva, N M; Aripovskiĭ, A V; Tkhagalizhokova, E M

    2015-01-01

    The article deals with per oral glucose tolerance test applied to 20 patients with arterial hypertension. The blood plasma was analyzed to detect content of individual fatty acids, double bounds, glucose, insulin and metabolites of fatty acids. In patients with different resistance to insulin content of non-etherized fatty acids decreased approximatively up to 3 times. Without insulin resistance secretion of insulin in 2 hours after glucose load increased up to 3 times and content of individual fatty acids decreases in greater extent. Under insulin resistance secretion of insulin increases up to 8 times and decreasing of content of fatty acids is less expressed. The decrease in blood plasma of content of oleic and linoleic fatty acids and double bounds reflects effectiveness of effect of insulin--blockade of hydrolysis of triglycerides in subcutaneous adipocytes. The concentration of insulin positively correlates with initial content of palmitic fatty acid in the pool of lipids of blood plasma.

  14. [The content of individual fatty acids and numbers of double bonds, insulin, C-peptide and unesterified fatty acids in blood plasma in testing tolerance to glucose].

    PubMed

    Titov, V N; Sazhina, N N; Aripovskiĭ, A V; Evteeva, N M; Tkhagalizhokova, É M; Parkhimovich, R M

    2014-10-01

    The glucose tolerance test demonstrates that content of unesterified fatty acids in blood plasma decreases up to three times and the content of oleic and linoleic acids is more decreased in the pool of fatty acids lipids. Out of resistance to insulin, hormone secretion increases up to three times. The decreasing of level of individual fatty acids occurs in a larger extent. Under resistance to insulin secretion of insulin is increasing up to eight times. The decreasing of level of each fatty acid is less expressed. The effect of insulin reflects decreasing of content of double bonds in blood plasma. The number of double bonds characterizes the degree of unsaturation of fatty acids in lipids of blood plasma. The higher number of double bonds is in the pool of unesterified fatty acids the more active is the effect of insulin. The hyper-secretion of insulin is directly proportional to content of palmitic fatty acid in lipids of blood plasma on fasting. According the phylogenetic theory of general pathology, the effect of insulin on metabolism of glucose is mediated by fatty acids. The insulin is blocking lipolysis in insulin-depended subcutaneous adipocytes and decreases content of unesterified fatty acids in blood plasma. The insulin is depriving all cells of possibility to absorb unesterified fatty acids and "forces" them to absorb glucose increasing hereby number of GLUT4 on cell membrane. The resistance to insulin is manifested in high concentration of unesterfied fatty acids, hyperinsulinemia, hyperalbuminemia and increasing of concentration of C-reactive protein-monomer. The resistance to insulin is groundlessly referred to as a symptom of diabetes mellitus type II. The resistance to insulin is only a functional disorder lasting for years. It can be successfully arrested. The diabetes mellitus is developed against the background of resistance to insulin only after long-term hyper-secretion of insulin and under emaciation and death of β-cells. The diabetes

  15. Addition of quadricyclane to C[sub 60]: Easy access to fullerene derivatives bearing a reactive double bond in the side chain

    SciTech Connect

    Prato, M. ); Maggini, M.; Scorrano, G. ); Lucchini, V. )

    1993-07-02

    The reaction of C[sub 60] with quadricyclane gives a stable 6,6 adduct which has been spectroscopically characterized. The double bond of the [2.2.1]bicycloheptene moiety reacts readily with electrophiles (e.g., PhSCl). Soon after the isolation and characterization of fullerene C[sub 60], the electrophilic character of this carbon cluster was disclosed by both experimental and theoretical results. Additions of several electrophiles to C[sub 60] have also been reported, but the conditions necessary for these reactions to occur led often to inseparable mixtures of products of multiple addition. In order to allow a controlled addition of electrophiles and to enrich the chemistry of functionalization, C[sub 60] has to be structurally modified. Herein the authors report a simple cycloaddition approach to a stable and characterizable C[sub 60] derivative, in which the incorporated olefinic moiety shows high reactivity toward electrophiles. 3 figs.

  16. Ambiphilic properties of SF5CF2CF2Br derived perfluorinated radical in addition reactions across carbon-carbon double bonds.

    PubMed

    Dudziński, Piotr; Matsnev, Andrej V; Thrasher, Joseph S; Haufe, Günter

    2015-03-06

    The extraordinary properties of the pentafluorosulfanyl (SF5) group attract attention of organic chemists. While numerous SF5-substituted compounds have been synthesized, the direct introduction of SF5(CF2)n moieties has remained almost unexplored. Our investigations revealed the ambiphilic character of the SF5CF2CF2 radical. Addition reactions to electron-rich or electron-deficient alkenes profit either from its electrophilic or nucleophilic properties. Thus, the readily available SF5CF2CF2Br proved to be a promising and versatile building block for the introduction of this perfluorinated moiety.

  17. Diastereoselective aziridination of chiral electron-deficient olefins with N-chloro-N-sodiocarbamates catalyzed by chiral quaternary ammonium salts.

    PubMed

    Murakami, Yuta; Takeda, Youhei; Minakata, Satoshi

    2011-08-05

    Chiral quaternary ammonium salt-catalyzed diastereoselective aziridination of electron-deficient olefins that possess a chiral auxiliary with N-chloro-N-sodiocarbamates was developed. The key to high stereoselectivity was found to be the employment of the "matching" stereochemical combination of chiral auxiliary/ammonium salt. For example, when 3-phenyl-(4R,7S)-4-methyl-7-isopropyl-4,5,6,7-tetrahydroindazole (L-menthopyrazole) as a chiral auxiliary and a cinchonidine-derived chiral ammonium salt as a catalyst were applied to the reaction system, perfect diastereoselectivity was realized. Furthermore, the preparation of enantiomerically pure aziridines by removal of the chiral auxiliary was demonstrated.

  18. Vibration analysis of bonded double-FGM viscoelastic nanoplate systems based on a modified strain gradient theory incorporating surface effects

    NASA Astrophysics Data System (ADS)

    Jamalpoor, Ali; Kiani, Ali

    2017-03-01

    On the basis of the modified strain gradient theory, the present paper deals with the theoretical analysis of the free vibration of coupled double-FGM viscoelastic nanoplates by Kelvin-Voigt visco-Pasternak medium. To establish static equilibrium of atoms on the each nanoplate surface, the effects of the surface layers are considered. The properties of material in the thickness direction vary according to the power low distribution. Kirchhoff plate assumption and Hamilton's variational principle are employed to achieve the partial differential equations for three different cases of vibration (out-of-phase, in-phase, and one nanoplate of the system being stationary) and corresponding boundary conditions. Navier's approach which satisfies the simply supported boundary conditions applied to analytically investigate the size effect on the natural frequencies of double-FGM viscoelastic nanoplate systems. Numerical studies are carried out to illustrate the influence of viscoelastic damping structural of the nanoplates, damping coefficient of the visco-Pasternak medium, independent length scale parameter, aspect ratio, surface properties, and other factors on the frequency behavior system. Some numerical results of this research illustrate that the frequencies may increase or decrease with respect to the sign of the surface properties of FGMs.

  19. Metal composition of layered double hydroxides (LDHs) regulating ClO(-)4 adsorption to calcined LDHs via the memory effect and hydrogen bonding.

    PubMed

    Lin, Yajie; Fang, Qile; Chen, Baoliang

    2014-03-01

    A series of calcined carbonate layered double hydroxides (CLDHs) with various metal compositions and different M(2+)/M(3+) ratios were prepared as adsorbents for perchlorate. Adsorption isotherms fit Langmuir model well, and the adsorption amount followed the order of MgAl-CLDHs ≥ MgFe-CLDHs > ZnAl-CLDHs. The isotherms of MgAl-CLDHs and MgFe-CLDHs displayed a two-step shape at low and high concentration ranges and increased with an increase in the M(2+)/M(3+) ratio from 2 to 4. The two-step isotherm was not observed for ZnAl-CLDHs, and the adsorption was minimally affected by the M(2+)/M(3+) ratio. The LDHs, CLDHs and the reconstructed samples were characterized by X-ray diffraction, SEM, FT-IR and Raman spectra to delineate the analysis of perchlorate adsorption mechanisms. The perchlorate adsorption of MgAl-CLDHs and MgFe-CLDHs was dominated by the structural memory effect and the hydrogen bonds between the free hydroxyl groups on the reconstructed-LDHs and the oxygen atoms of the perchlorates. For ZnAl-CLDHs, the perchlorate adsorption was controlled by the structural memory effect only, as the hydroxyl groups on the hydroxide layers preferred to form strong hydrogen bonds with carbonate over perchlorate, which locked the intercalated perchlorate into a more confined nano-interlayer. Several distinct binding mechanisms of perchlorate by CLDHs with unique M(2+) ions were proposed.

  20. Structure-performance correlations of organic dyes with an electron-deficient diphenylquinoxaline moiety for dye-sensitized solar cells.

    PubMed

    Li, Sie-Rong; Lee, Chuan-Pei; Yang, Po-Fan; Liao, Chia-Wei; Lee, Mandy M; Su, Wei-Lin; Li, Chun-Ting; Lin, Hao-Wu; Ho, Kuo-Chuan; Sun, Shih-Sheng

    2014-08-04

    The high performances of dye-sensitized solar cells (DSSCs) based on seven new dyes are disclosed. Herein, the synthesis and electrochemical and photophysical properties of a series of intentionally designed dipolar organic dyes and their application in DSSCs are reported. The molecular structures of the seven organic dyes are composed of a triphenylamine group as an electron donor, a cyanoacrylic acid as an electron acceptor, and an electron-deficient diphenylquinoxaline moiety integrated in the π-conjugated spacer between the electron donor and acceptor moieties. The DSSCs based on the dye DJ104 gave the best overall cell performance of 8.06 %; the efficiency of the DSSC based on the standard N719 dye under the same experimental conditions was 8.82 %. The spectral coverage of incident photon-to-electron conversion efficiencies extends to the onset at the near-infrared region due to strong internal charge-transfer transition as well as the effect of electron-deficient diphenylquinoxaline to lower the energy gap in these organic dyes. A combined tetraphenyl segment as a hydrophobic barrier in these organic dyes effectively slows down the charge recombination from TiO2 to the electrolyte and boosts the photovoltage, comparable to their Ru(II) counterparts. Detailed spectroscopic studies have revealed the dye structure-cell performance correlations, to allow future design of efficient light-harvesting organic dyes.

  1. Bond-rearrangement and ionization mechanisms in the photo-double-ionization of simple hydrocarbons (C2H4, C2H3F, and 1,1-C2H2F2) near and above threshold

    DOE PAGES

    Gaire, B.; Gatton, A. S.; Wiegandt, F.; ...

    2016-09-14

    We have investigated bond-rearrangement driven by photo-double-ionization (PDI) near and above the double ionization threshold in a sequence of carbon-carbon double bonded hydrocarbon molecules: ethylene, fluoroethylene, and 1,1-difluoroethylene. We employ the kinematically complete cold target recoil ion momentum spectroscopy (COLTRIMS) method to resolve all photo-double-ionization events leading to two-ionic fragments. We observe changes in the branching ratios of different dissociative ionization channels depending on the presence of none, one, or two fluorine atoms. The role of the fluorine atom in the bond-rearrangement channels is intriguing as evident by the re-ordering of the threshold energies of the PDI in the fluorinatedmore » molecules. These effects offer a compelling argument that the electronegativity of the fluorine (or the polarity of the molecule) strongly influences the potential energy surfaces of the molcules and drives bond-rearrangement during the dissociation process. The energy sharing and the relative angle between the 3D-momentum vectors of the two electrons provide clear evidence of direct and indirect PDI processes.« less

  2. Bond-rearrangement and ionization mechanisms in the photo-double-ionization of simple hydrocarbons (C2H4, C2H3F, and 1,1-C2H2F2) near and above threshold

    SciTech Connect

    Gaire, B.; Gatton, A. S.; Wiegandt, F.; Neff, J.; Janke, C.; Zeller, S.; Reedy, D.; Rajput, J.; Ben-Itzahk, I.; Landers, A. L.; Belkacem, A.; Weber, Th.

    2016-09-14

    We have investigated bond-rearrangement driven by photo-double-ionization (PDI) near and above the double ionization threshold in a sequence of carbon-carbon double bonded hydrocarbon molecules: ethylene, fluoroethylene, and 1,1-difluoroethylene. We employ the kinematically complete cold target recoil ion momentum spectroscopy (COLTRIMS) method to resolve all photo-double-ionization events leading to two-ionic fragments. We observe changes in the branching ratios of different dissociative ionization channels depending on the presence of none, one, or two fluorine atoms. The role of the fluorine atom in the bond-rearrangement channels is intriguing as evident by the re-ordering of the threshold energies of the PDI in the fluorinated molecules. These effects offer a compelling argument that the electronegativity of the fluorine (or the polarity of the molecule) strongly influences the potential energy surfaces of the molcules and drives bond-rearrangement during the dissociation process. The energy sharing and the relative angle between the 3D-momentum vectors of the two electrons provide clear evidence of direct and indirect PDI processes.

  3. Bond-rearrangement and ionization mechanisms in the photo-double-ionization of simple hydrocarbons (C2H4 , C2H3F , and 1 ,1 -C2H2F2 ) near and above threshold

    NASA Astrophysics Data System (ADS)

    Gaire, B.; Gatton, A.; Wiegandt, F.; Neff, J.; Janke, C.; Zeller, S.; Reedy, D.; Rajput, J.; Ben-Itzhak, I.; Landers, A. L.; Belkacem, A.; Weber, Th.

    2016-09-01

    We investigate bond-rearrangement driven by photo-double-ionization (PDI) near and above the double-ionization threshold in a sequence of carbon-carbon double-bonded hydrocarbon molecules: ethylene, fluoroethylene, and 1,1-difluoroethylene. We employ the kinematically complete cold target recoil ion momentum spectroscopy method to resolve all photo-double-ionization events leading to two-ion fragments. We observe changes in the branching ratios of different dissociative ionization channels depending on the presence of no, one, or two fluorine atoms. The role of the fluorine atom in the bond-rearrangement channels is intriguing, as evident by the reordering of the threshold energies of the PDI in the fluorinated molecules. These effects offer a compelling argument that the electronegativity of the fluorine (or the polarity of the molecule) strongly influences the potential energy surfaces of the molecules and drives bond rearrangement during the dissociation process. The energy sharing and the relative angle between the three-dimensional momentum vectors of the two electrons enable us to distinguish between knockout and other ionization mechanisms of the PDI processes.

  4. 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.

  5. Making Fe(BPBP)-catalyzed C-H and C[double bond, length as m-dash]C oxidations more affordable.

    PubMed

    Yazerski, Vital A; Spannring, Peter; Gatineau, David; Woerde, Charlotte H M; Wieclawska, Sara M; Lutz, Martin; Kleijn, Henk; Gebbink, Robertus J M Klein

    2014-04-07

    The limited availability of catalytic reaction components may represent a major hurdle for the practical application of many catalytic procedures in organic synthesis. In this work, we demonstrate that the mixture of isomeric iron complexes [Fe(OTf)2(mix-BPBP)] (mix-1), composed of Λ-α-[Fe(OTf)2(S,S-BPBP)] (S,S-1), Δ-α-[Fe(OTf)2(R,R-BPBP)] (R,R-1) and Δ/Λ-β-[Fe(OTf)2(R,S-BPBP)] (R,S-1), is a practical catalyst for the preparative oxidation of various aliphatic compounds including model hydrocarbons and optically pure natural products using hydrogen peroxide as an oxidant. Among the species present in mix-1, S,S-1 and R,R-1 are catalytically active, act independently and represent ca. 75% of mix-1. The remaining 25% of mix-1 is represented by mesomeric R,S-1 which nominally plays a spectator role in both C-H and C[double bond, length as m-dash]C bond oxidation reactions. Overall, this mixture of iron complexes displays the same catalytic profile as its enantiopure components that have been previously used separately in sp(3) C-H oxidations. In contrast to them, mix-1 is readily available on a multi-gram scale via two high yielding steps from crude dl/meso-2,2'-bipyrrolidine. Next to its use in C-H oxidation, mix-1 is active in chemospecific epoxidation reactions, which has allowed us to develop a practical catalytic protocol for the synthesis of epoxides.

  6. Computational study of the double C-Cl bond activation of dichloromethane and phosphine alkylation at [CoCl(PR3)3].

    PubMed

    Algarra, Andrés G; Braunstein, Pierre; Macgregor, Stuart A

    2013-03-28

    Density functional theory calculations have been employed to model the double C-Cl bond activation of CH(2)Cl(2) at [CoCl(PR(3))(3)] to give [CoCl(3)(CH(2)PR(3))(PR(3))(2)]. Calculations incorporating dichloromethane solution (PCM approach) on a [CoCl(PMe(3))(3)] model system showed the two C-Cl cleavage steps to involve different mechanisms. The first C-Cl cleavage step occurs on the triplet surface and proceeds via Cl abstraction with a barrier of 19.1 kcal mol(-1). Radical recombination would then give singlet mer,trans-[CoCl(2)(CH(2)Cl)(PMe(3))(3)] with an overall free energy change of +1.8 kcal mol(-1). Alternative C-Cl activation processes based on nucleophilic attack by the Co centre at dichloromethane with loss of Cl(-) have significantly higher barriers. The second C-Cl cleavage occurs via nucleophilic attack of PMe(3) at the CH(2)Cl ligand with formation of a new P-C bond and displacement of Cl(-). This may either occur in an intermolecular fashion (after prior PMe(3) dissociation) or intramolecularly. Both processes have similar barriers of ca. 12 kcal mol(-1). The comproportionation of [CoCl(3)(CH(2)PMe(3))(PMe(3))(2)] with [CoCl(PMe(3))(3)] to give [CoCl(2)(CH(2)PMe(3))(PMe(3))], [CoCl(2)(PMe(3))(2)] and 2 PMe(3) is computed to be strongly exergonic, consistent with the observation of this process in analogous experimental systems.

  7. Temperature-induced melting of double-stranded DNA in the absence and presence of covalently bonded antitumour drugs: insight from molecular dynamics simulations.

    PubMed

    Bueren-Calabuig, Juan A; Giraudon, Christophe; Galmarini, Carlos M; Egly, Jean Marc; Gago, Federico

    2011-10-01

    The difference in melting temperature of a double-stranded (ds) DNA molecule in the absence and presence of bound ligands can provide experimental information about the stabilization brought about by ligand binding. By simulating the dynamic behaviour of a duplex of sequence 5'-d(TAATAACGGATTATT)·5'-d(AATAATCCGTTATTA) in 0.1 M NaCl aqueous solution at 400 K, we have characterized in atomic detail its complete thermal denaturation profile in <200 ns. A striking asymmetry was observed on both sides of the central CGG triplet and the strand separation process was shown to be strongly affected by bonding in the minor groove of the prototypical interstrand crosslinker mitomycin C or the monofunctional tetrahydroisoquinolines trabectedin (Yondelis), Zalypsis and PM01183. Progressive helix unzipping was clearly interspersed with some reannealing events, which were most noticeable in the oligonucleotides containing the monoadducts, which maintained an average of 6 bp in the central region at the end of the simulations. These significant differences attest to the demonstrated ability of these drugs to stabilize dsDNA, stall replication and transcription forks, and recruit DNA repair proteins. This stabilization, quantified here in terms of undisrupted base pairs, supports the view that these monoadducts can functionally mimic a DNA interstrand crosslink.

  8. Temperature-induced melting of double-stranded DNA in the absence and presence of covalently bonded antitumour drugs: insight from molecular dynamics simulations

    PubMed Central

    Bueren-Calabuig, Juan A.; Giraudon, Christophe; Galmarini, Carlos M.; Egly, Jean Marc; Gago, Federico

    2011-01-01

    The difference in melting temperature of a double-stranded (ds) DNA molecule in the absence and presence of bound ligands can provide experimental information about the stabilization brought about by ligand binding. By simulating the dynamic behaviour of a duplex of sequence 5′-d(TAATAACGGATTATT)·5′-d(AATAATCCGTTATTA) in 0.1 M NaCl aqueous solution at 400 K, we have characterized in atomic detail its complete thermal denaturation profile in <200 ns. A striking asymmetry was observed on both sides of the central CGG triplet and the strand separation process was shown to be strongly affected by bonding in the minor groove of the prototypical interstrand crosslinker mitomycin C or the monofunctional tetrahydroisoquinolines trabectedin (Yondelis®), Zalypsis® and PM01183®. Progressive helix unzipping was clearly interspersed with some reannealing events, which were most noticeable in the oligonucleotides containing the monoadducts, which maintained an average of 6 bp in the central region at the end of the simulations. These significant differences attest to the demonstrated ability of these drugs to stabilize dsDNA, stall replication and transcription forks, and recruit DNA repair proteins. This stabilization, quantified here in terms of undisrupted base pairs, supports the view that these monoadducts can functionally mimic a DNA interstrand crosslink. PMID:21727089

  9. Molecular structures and hydrogen bonding in the crystalline hydrates of two flexible double betaines with different quaternary ammonio groups in the adipic acid skeleton

    NASA Astrophysics Data System (ADS)

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

    1995-12-01

    Crystalline dihydrates of two flexible double betaines -O 2CCH(R)CH 2CH 2CH(R)CO -2 ( 1, R = Me 3N +, 2, R = C 5H 5N +) have been characterized by single-crystal X-ray analysis. Both compounds crystallize in the monoclinic space group {P2 1}/{c} with a = 7.463(4), b = 10.312(6), c = 9.978(5) Å, β = 90.18(5)°, Z = 2 for 1·2H 2O and a = 9.063(2), b = 7.665(1), c = 11.962(1) Å, β = 94.89(1)°, Z = 2 for 2·2H 2O. Both betaine molecules occupy l¯ sites but differ with regard to the orientation of the carboxylate groups and ammonio groups. In each crystal structure, the formation of donor hydrogen bonds from the water molecules to adjacent carboxylate groups gives rise to an infinte two-dimensional network composed of a packing of identical 26-membered rings.

  10. 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

  11. Investigation of double bond conversion, mechanical properties, and antibacterial activity of dental resins with different alkyl chain length quaternary ammonium methacrylate monomers (QAM).

    PubMed

    He, Jingwei; Söderling, Eva; Vallittu, Pekka K; Lassila, Lippo V J

    2013-01-01

    In order to endow dental resin with antibacterial activity, a series of antibacterial quaternary ammonium methacrylate monomers (QAM) with different substituted alkyl chain length (from 10 to 18) were incorporated into commonly used 2,2-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)-phenyl]propane (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA) (50 wt/50 wt) dental resin as immobilized antibacterial agents. Double bond conversion (DC), flexural strength (FS) and modulus (FM), and young and mature biofilms inhibition effectiveness of prepared dental resins were studied and Bis-GMA/TEGDMA without QAM was used as reference. Results showed that there was no significant difference on DC, FS, and FM between copolymer with and without 5 wt% QAM. Substituted alkyl chain length of QAM had no influence on DC, FS, and FM of copolymer, but had influence on antibacterial activity of copolymer. Antibacterial activity of copolymer increased with increasing of substituted alkyl chain length of QAM, and the sequence followed as 5%C10 < 5%C11 ≈ 5%C12 < 5%C16 ≈ 5%C18. Copolymers containing C18 and C16 had the best inhibition effectiveness on both young biofilm and mature biofilm, copolymers containing C12 and C11 only had inhibition effectiveness on young biofilm and copolymer containing C10 had none inhibition effectiveness on neither young biofilm nor mature biofilm.

  12. Respective contributions of polar vs enthalpy effects in the addition/fragmentation of mercaptobenzoxazole-derived thiyl radicals and analogues to double bonds.

    PubMed

    Lalevée, J; Allonas, X; Morlet-Savary, F; Fouassier, J P

    2006-10-19

    The formation and the reactivity of three selected sulfur-centered radicals formed from mercaptobenzoxazole, mercaptobenzimidazole, and mercaptobenzothiazole toward four double bonds (methyl acrylate, acrylonitrile, vinyl ether, and vinyl acetate) are investigated. The reversibility of the addition/fragmentation reaction in these widely used photoinitiating systems of radical polymerization was studied, for the first time, through the measurement of the corresponding rate constants by time-resolved laser spectroscopy. The combination of these results with quantum mechanical calculations clearly evidences that, contrary to previous studies on other aryl thiyl radicals, the addition rate constants (ka) are governed here by the polar effects associated with the very high electrophilic character of these radicals. However, interestingly, the back-fragmentation reaction (k-a) is mainly influenced by the enthalpy effects as supported by the relationship between the rate constants and the addition reaction enthalpy DeltaHR. The addition and fragmentation rate constants calculated from the transition state theory (TST) are in satisfactory agreement with the experimental ones. Therefore, molecular orbital (MO) calculations offered new opportunities for a better understanding of the sulfur-centered radical reactivity.

  13. The behavior of pyrrolyl ligands within the rare-earth metal alkyl complexes. Insertion of C=N and C=O double bonds into Ln-sigma-C bonds.

    PubMed

    Yang, Yi; Cui, Dongmei; Chen, Xuesi

    2010-04-28

    This paper presents some unusual reactions of lanthanide tris(alkyl)s or lanthanide mono-Cp' (Cp' = (C(5)Me(4))SiMe(3)) bis(alkyl)s with pyrrolyl ligands, and the eta(5)- or eta(1)-coordination mode of the pyrrolyl ring, as well as C=N and C=O double bonds insertion into Ln-sigma-C moities. N,N,O-tridentate ligand HL(1), 2-(2-CH(3)OC(6)H(3)N=CH)-C(4)H(3)NH, was prepared. Treatment of HL(1) with rare-earth metal tris(alkyl)s, Ln(CH(2)SiMe(3))(3)(THF)(2), generated centrosymmetric bimetallic (pyrrolylaldiminato)lanthanide mono(alkyl) complexes [{2-(2-CH(3)OC(6)H(3)NC(H)R)-C(4)H(3)N}LnR](2) (1a: Ln = Y; 1b: Ln = Lu) (R = CH(2)SiMe(3)). In this process, HL(1) was deprotonated by the metal alkyl and its imino C=N group was deactivated by the intramolecular alkylation, generating dianionic species that bridged the two metal alkyl units in eta(5)/eta(1):kappa(1) modes. When the reaction was carried out in dimethoxyethane (DME), asymmetric complex [2-(2-CH(3)OC(6)H(3)NC(H)R)-C(4)H(3)N](2)Y(2)R(2)(DME) (2) was given. Furthermore, the reaction of alkyl complex 1b and benzophenone (Ph(2)C=O) afforded alkyl-insertion product [{2-(2-CH(3)OC(6)H(3)NC(H)R)-C(4)H(3)N}LuOC(R)Ph(2)](2) (3). Both the intermolecular alkylation and the pyrrole's behavior as the hetero-cyclopentadienyl ligand were also observed in complexes 2 and 3. HL(1) reacted with (eta(5)-Cp')Y(CH(2)SiMe(3))(2)(THF) (E) to form a mixed ligands supported alkyl complex [(eta(5)-Cp')(L(1))]Y(CH(2)SiMe(3))(THF) (4), whilst complex E was treated with 2-(2,6-iPr(2)C(6)H(3)N=CH)-C(4)H(3)NH (HL(2)) to yield [(eta(5)-Cp')(L(2))]Y(CH(2)SiMe(3))(THF) (5). However, reaction of E and 2-(Me(2)NCH(2))-C(4)H(3)NH (HL(3)) afforded Y[(eta(5)-Cp')(L(3))(2)] (6), and ligand redistribution was found in this process. The molecular structures of complexes 5 and 6 were confirmed by X-ray diffraction, which indicated that the C=N double bond survived and the pyrrolyl ring coordinated to the metal center in eta(1)-mode.

  14. Reversible methanol addition to copper Schiff base complexes: a kinetic, structural and spectroscopic study of reactions at azomethine C[double bond, length as m-dash]N bonds.

    PubMed

    Zhang, Wuyu; Saraei, Nina; Nie, Hanlin; Vaughn, John R; Jones, Alexis S; Mashuta, Mark S; Buchanan, Robert M; Grapperhaus, Craig A

    2016-10-12

    The reversible methanolysis of an azomethine C[double bond, length as m-dash]N in a series of copper(ii) Schiff base complexes has been investigated through combined spectroscopic, structural, and kinetic studies. Pentadentate copper(ii) complexes [L1-Cu(X)]Y (L1 = 1,2-bis[(1-methyl-2-imidazolyl)methyleneamino]ethane; X = Y = ClO4(-) (1); X = Y = TfO(-) (2); X = Y = BF4(-) (3); X = H2O, Y = (ClO4(-))2 (4) spontaneously add methanol in a ligand centered reaction to yield stable, isolable hemiaminal ether product complexes 5-8. In methanol free solution, 5-8 spontaneously release alcohol to regenerate 1-4. The methanol addition reaction is first-order in methanol and first-order in complex with second-order rate constants varying from 1.1 × 10(-4) to 187 × 10(-4) M(-1) s(-1) dependent on the donor ability of the axial ligand. Rate constants for methanol elimination vary from 0.67 to 3.7 × 10(-4) s(-1) with dependence on the counterion and water content of the solvent. Equilibrium constants for methanolysis range from 1.5 to 51 M(-1). Structural comparisons of the Schiff base complexes 1-4 and the hemiaminal ether complexes 5-8 suggest methanol addition is favored by the release of ligand strain associated with three planar five-membered chelates in 1-4.

  15. [2,3]-Wittig rearrangement of enantiomerically enriched 3-substituted 1-propenyloxy-1-phenyl-2-propen-1-yl carbanions: effect of heteroatoms and conjugating groups on planarization of an alpha-oxy-benzylcarbanion through a double bond.

    PubMed

    Sasaki, Michiko; Ikemoto, Hidaka; Kawahata, Masatoshi; Yamaguchi, Kentaro; Takeda, Kei

    2009-01-01

    Don't get trapped: The effect of conjugating electron-withdrawing groups and alpha-anion-stabilizing heteroatom substituents on configurational stability of chiral carbanions through a double bond was examined on the basis of extent of chirality transfer in intramolecular trapping in [2,3]-Wittig rearrangement of chiral 3-substituted 1-propenyloxy-1-phenyl-2-propen-1-yl carbanions (see scheme).The effect of conjugating electron-withdrawing groups and alpha-anion-stabilizing heteroatom substituents on configurational stability of chiral carbanions through a double bond was examined on the basis of extent of chirality transfer in intramolecular trapping in [2,3]-Wittig rearrangement of chiral 3-substituted 1-propenyloxy-1-phenyl-2-propen-1-yl carbanions.

  16. 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 PAGES

    Welz, Oliver; Savee, John D.; Osborn, David L.; ...

    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

  17. Solvent effects on the a sub g C double bond C stretching mode in the 2 sup 1 A sub g sup minus excited state of. beta. -carotene and two derivatives: Picosecond time-resolved resonance Raman spectroscopy

    SciTech Connect

    Noguchi, T.; Hayashi, H. Univ. of Tokyo ); Tasumi, M. ); Atkinson, G.H. Hebrew Univ., Jerusalem )

    1991-04-18

    Picosecond time-resolved resonance Raman spectra in the C{double bond}C stretching region are presented for {beta}-carotene and two of its derivatives, {beta}-apo-8{prime}-carotenal and ethyl {beta}-apo-8{prime}-carotenoate. The solvent effects on the Franck-Condon-active a{sub g} C{double bond}C stretching mode in the {sup 1}A{sub g}{sup {minus}} ground state (S{sub 0}) and the 2{sup 1}A{sub g}{sup {minus}} excited state (S{sub 1}) of each carotenoid are described. The C{double bond}C stretching frequencies in S{sub 1} are affected by the solvent and show a correlation with the absorption maxima of the S{sub 2} ({sup 1}B{sub u}{sup +}) {l arrow} S{sub 0} transition, while those in S{sub 0} are not significantly affected. These results are interpreted in terms of the vibronic coupling among the S{sub 0}, S{sub 1}, and S{sub 2} electronic states, the solvent effect on the energy of the S{sub 1} and S{sub 2} states, and the structures of carotenoid molecules.

  18. Effects of electron-deficient beta-diketiminate and formazan supporting ligands on copper(I)-mediated dioxygen activation.

    PubMed

    Hong, Sungjun; Hill, Lyndal M R; Gupta, Aalo K; Naab, Benjamin D; Gilroy, Joe B; Hicks, Robin G; Cramer, Christopher J; Tolman, William B

    2009-05-18

    Copper(I) complexes of a diketiminate featuring CF(3) groups on the backbone and dimethylphenyl substituents (4) and a nitroformazan (5) were synthesized and shown by spectroscopy, X-ray crystallography, cyclic voltammetry, and theory to contain copper(I) sites electron-deficient relative to those supported by previously studied diketiminate complexes comprising alkyl or aryl backbone substituents. Despite their electron-poor nature, oxygenation of LCu(CH(3)CN) (L = 4 or 5) at room temperature yielded bis(hydroxo)dicopper(II) compounds and at -80 degrees C yielded bis(mu-oxo)dicopper complexes that were identified on the basis of UV-vis and resonance Raman spectroscopy, spectrophotometric titration results (2:1 Cu/O(2) ratio), electron paramagnetic resonance spectroscopy (silent), and density functional theory calculations. The bis(mu-oxo)dicopper complex supported by 5 exhibited unusual spectroscopic properties and decayed via a novel intermediate proposed to be a metallaverdazyl radical complex, findings that highlight the potential for the formazan ligand to exhibit "noninnocent" behavior.

  19. 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

  20. Palladium-catalyzed cross-coupling of aryl fluorides with N-tosylhydrazones via C-F bond activation.

    PubMed

    Luo, Haiqing; Wu, Guojiao; Xu, Shuai; Wang, Kang; Wu, Chaoqiang; Zhang, Yan; Wang, Jianbo

    2015-09-04

    A palladium-catalyzed cross-coupling reaction of electron-deficient aryl fluorides with aryl N-tosylhydrazones has been reported. Mechanistically, this approach involves C-F bond activation and migratory insertion of palladium carbene as the two key steps.

  1. X-ray Crystal Structure of a Metalled Double-Helix Generated by Infinite and Consecutive C*-Ag(I) -C* (C*:N(1) -Hexylcytosine) Base Pairs through Argentophilic and Hydrogen Bond Interactions.

    PubMed

    Terrón, Angel; Moreno-Vachiano, Blas; Bauzá, Antonio; García-Raso, Angel; Fiol, Juan Jesús; Barceló-Oliver, Miquel; Molins, Elies; Frontera, Antonio

    2017-02-10

    The synthesis of a metalled double-helix containing exclusively silver-mediated C*-C* base pairs is reported herein (C*=N(1) hexylcytosine). Remarkably, it is the first crystal structure containing infinite and consecutive C*-Ag(I) -C* base pairs that form a double helix. The Ag(I) ion occupies the center between two C* residues with N(3)-Ag bond lengths of 2.1 Å and short Ag(I) -Ag(I) distances (3.1 Å) suggesting an interesting argentophilic attraction as a stabilization source of the helical disposition. The solid-state structure is further stabilized by metal-mediated base-pairs, hydrogen bonding and π-stacking interactions. Moreover, the angle N(3)-Ag-N(3) is almost linear in the [Ag(N(1) hexylcytosine)2 ](+) motif and the bases are not coplanar, thus generating a double-strand helical aggregate in the solid state. The noncovalent and argentophilic interactions have been rationalized based on DFT calculations.

  2. Double bond in the side chain of 1alpha,25-dihydroxy-22-ene-vitamin D(3) is reduced during its metabolism: studies in chronic myeloid leukemia (RWLeu-4) cells and rat kidney.

    PubMed

    Sunita Rao, D; Balkundi, D; Uskokovic, M R; Tserng, K; Clark, J W; Horst, R L; Satyanarayana Reddy, G

    2001-08-01

    1alpha,25-Dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] is mainly metabolized via the C-24 oxidation pathway and undergoes several side chain modifications which include C-24 hydroxylation, C-24 ketonization, C-23 hydroxylation and side chain cleavage between C-23 and C-24 to form the final product, calcitroic acid. In a recent study we reported that 1alpha,25-dihydroxyvitamin D(2) [1alpha,25(OH)(2)D(2)] like 1alpha,25(OH)(2)D(3), is also converted into the same final product, calcitroic acid. This finding indicated that 1alpha,25(OH)(2)D(2) also undergoes side chain cleavage between C-23 and C-24. As the side chain of 1alpha,25(OH)(2)D(2) when compared to the side chain of 1alpha,25(OH)(2)D(3), has a double bond between C-22 and C-23 and an extra methyl group at C-24 position, it opens the possibility for both (a) double bond reduction and (b) demethylation to occur during the metabolism of 1alpha,25(OH)(2)D(2). We undertook the present study to establish firmly the possibility of double bond reduction in the metabolism of vitamin D(2) related compounds. We compared the metabolism of 1alpha,25-dihydroxy-22-ene-vitamin D(3) [1alpha,25(OH)(2)-22-ene-D(3)], a synthetic vitamin D analog whose side chain differs from that of 1alpha,25(OH)(2)D(3) only through a single modification namely the presence of a double bond between C-22 and C-23. Metabolism studies were performed in the chronic myeloid leukemic cell line (RWLeu-4) and in the isolated perfused rat kidney. Our results indicate that both 1alpha,25(OH)(2)-22-ene-D(3) and 1alpha,25(OH)(2)D(3) are converted into common metabolites namely, 1alpha,24(R),25-trihydroxyvitamin D(3) [1alpha,24(R),25(OH)(3)D(3)], 1alpha,25-dihydroxy-24-oxovitamin D(3) [1alpha,25(OH)(2)-24-oxo-D(3)], 1alpha,23(S),25-trihydroxy-24-oxovitamin D(3) and 1alpha,23-dihydroxy-24,25,26,27-tetranorvitamin D(3). This finding indicates that the double bond in the side chain of 1alpha,25(OH)(2)-22-ene-D(3) is reduced during its metabolism. Along with

  3. The concept of bond order

    NASA Astrophysics Data System (ADS)

    Elliott, Robert J.; Richards, W. Graham

    A method for obtaining precise charge densities in defined regions of space from ab initio molecular wavefunctions is employed to place the concept of bond order on a firm theoretical footing. The bond orders obtained for carbon—carbon bonds in a range of organic compounds are assessed: those for buta-1,3-diene confirm that it consists of essentially localised double and single bonds.

  4. 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

  5. Sequential and selective hydrogenation of the C(alpha)-C(beta) and M-C(alpha) double bonds of an allenylidene ligand coordinated to osmium: new reaction patterns between an allenylidene complex and alcohols.

    PubMed

    Bolaño, Tamara; Castarlenas, Ricardo; Esteruelas, Miguel A; Oñate, Enrique

    2007-07-18

    Complex [OsH(=C=C=CPh2)(CH3CN)2(PiPr3)2]BF4 (1) reacts with primary and secondary alcohols to give the corresponding dehydrogenated alcohols and the hydride-carbene derivative [OsH(=CHCH=CPh2)(CH3CN)2(PiPr3)2]BF4 (2), as a result of hydrogen transfer reactions from the alcohols to the Calpha-Cbeta double bond of the allenylidene ligand of 1. The reactions with phenol and t-butanol, which do not contain any beta-hydrogen, afford the alkoxy-hydride-carbyne complexes [OsH(OR)(CCH=CPh2)(CH3CN)(PiPr3)2]BF4 (R = Ph (3), tBu (4)), as a consequence of the 1,3-addition of the O-H bond of the alcohols to the metallic center and the Cbeta atom of the allenylidene of 1. On the basis of the reactions of 1 with these tertiary alcohols, deuterium labeling experiments, and DFT calculations, the mechanism of the hydrogenation is proposed. In acetonitrile under reflux, the Os-C double bond of 2 undergoes hydrogenation to give 1,1-diphenylpropene and [Os{CH2CH(CH3)PiPr2(CH3CN)3(PiPr3)]BF4 (11), containing a metalated phosphine ligand. This reaction is a first-order process with activation parameters of DeltaH = 89.0 +/- 6.3 kJ mol-1 and DeltaS = -43.5 +/- 9.6 J mol-1 K-1. The X-ray structures of 2 and 3 are also reported.

  6. Intermolecular cross-double-michael addition between nitro and carbonyl activated olefins as a new approach in C-C bond formation.

    PubMed

    Sun, Xiaohua; Sengupta, Sujata; Petersen, Jeffrey L; Wang, Hong; Lewis, James P; Shi, Xiaodong

    2007-10-25

    A novel intermolecular cross-double-Michael addition between nitro and carbonyl activated olefins has been developed through Lewis base catalysis. The reaction took place with a large group of beta-alkyl nitroalkenes and alpha,beta-unsaturated ketone/esters, producing an allylic nitro compound in good to excellent yields.

  7. Efficient Cu-catalyzed atom transfer radical addition reactions of fluoroalkylsulfonyl chlorides with electron-deficient alkenes induced by visible light.

    PubMed

    Tang, Xiao-Jun; Dolbier, William R

    2015-03-27

    Fluoroalkylsulfonyl chlorides, R(f)SO2Cl, in which R(f)=CF3, C4F9, CF2H, CH2F, and CH2CF3, are used as a source of fluorinated radicals to add fluoroalkyl groups to electron-deficient, unsaturated carbonyl compounds. Photochemical conditions, using Cu mediation, are used to produce the respective α-chloro-β-fluoroalkylcarbonyl products in excellent yields through an atom transfer radical addition (ATRA) process. Facile nucleophilic replacement of the α-chloro substituent is shown to lead to further diverse functionalization of the products.

  8. 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%.

  9. Stereoselective synthesis of 3-methyleneisoindolin-1-ones via base-catalyzed intermolecular reactions of electron-deficient alkynes with N-hydroxyphthalimides.

    PubMed

    Chen, Xin; Ge, Fei-Fei; Lu, Tao; Zhou, Qing-Fa

    2015-03-20

    Highly stereoselective intermolecular reactions of electron-deficient alkynes with N-hydroxyphthalimides for efficient construction of N-unprotected 3-methyleneisoindolin-1-ones have been developed through base catalytic strategies. The reaction of alkynoates with N-hydroxyphthalimides catalyzed by Bu3P in DMF at 150 °C gave the corresponding 3-methyleneisoindolin-1-ones with a (Z)-configuration, while the reaction of alkynoates with N-hydroxyphthalimides catalyzed by K2CO3 in DMF at 60 °C gave the corresponding 3-methyleneisoindolin-1-ones with an (E)-configuration, and (Z)-3-methyleneisoindolin-1-ones were obtained when alkyne ketones reacted with N-hydroxyphthalimide.

  10. 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.

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

    PubMed

    Jacobsen, Heiko

    2009-06-07

    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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Carbon-to-metal bonds: Electrochemical reduction of 2-butenenitrile

    NASA Astrophysics Data System (ADS)

    Deniau, Guy; Azoulay, Laurent; Jégou, Pascale; Le Chevallier, Gilles; Palacin, Serge

    2006-02-01

    2-Butenenitrile belongs to the large family of electron deficient vinylic monomers that usually form 100 to 500 nm thick grafted polymer films by electroreduction. However, 2-butenenitrile exhibits a slightly acidic hydrogen atom on its CH 3 group that inhibits the anionic polymerization usually observed with 'classical' organic monomers such as its isomer methacrylonitrile. 2-Butenenitrile thus gives nanometer thick grafted film by electroreduction, essentially composed of a mixture of monomers, dimers and trimers and in the same way, allows an easy observation by XPS of the chemical signature of the grafting, i.e. the carbon-to-nickel bond, observed at 283.6 eV.

  15. Separating electrophilicity and Lewis acidity: the synthesis, characterization, and electrochemistry of the electron deficient tris(aryl)boranes B(C6F5)(3-n)(C6Cl5)n (n = 1-3).

    PubMed

    Ashley, Andrew E; Herrington, Thomas J; Wildgoose, Gregory G; Zaher, Hasna; Thompson, Amber L; Rees, Nicholas H; Krämer, Tobias; O'Hare, Dermot

    2011-09-21

    A new family of electron-deficient tris(aryl)boranes, B(C(6)F(5))(3-n)(C(6)Cl(5))(n) (n = 1-3), has been synthesized, permitting an investigation into the steric and electronic effects resulting from the gradual replacement of C(6)F(5) with C(6)Cl(5) ligands. B(C(6)F(5))(2)(C(6)Cl(5)) (3) is accessed via C(6)Cl(5)BBr(2), itself prepared from donor-free Zn(C(6)Cl(5))(2) and BBr(3). Reaction of C(6)Cl(5)Li with BCl(3) in a Et(2)O/hexane slurry selectively produced B(C(6)Cl(5))(2)Cl, which undergoes B-Cl exchange with CuC(6)F(5) to afford B(C(6)F(5))(C(6)Cl(5))(2) (5). While 3 forms a complex with H(2)O, which can be rapidly removed under vacuum or in the presence of molecular sieves, B(C(6)Cl(5))(3) (6) is completely stable to refluxing toluene/H(2)O for several days. Compounds 3, 5, and 6 have been structurally characterized using single crystal X-ray diffraction and represent the first structure determinations for compounds featuring B-C(6)Cl(5) bonds; each exhibits a trigonal planar geometry about B, despite having different ligand sets. The spectroscopic characterization using (11)B, (19)F, and (13)C NMR indicates that the boron center becomes more electron-deficient as n increases. Optimized structures of B(C(6)F(5))(3-n)(C(6)Cl(5))(n) (n = 0-3) using density functional theory (B3LYP/TZVP) are all fully consistent with the experimental structural data. Computed (11)B shielding constants also replicate the experimental trend almost quantitatively, and the computed natural charges on the boron center increase in the order n = 0 (0.81) < n = 1 (0.89) < n = 2 (1.02) < n = 3 (1.16), supporting the hypothesis that electrophilicity increases concomitantly with substitution of C(6)F(5) for C(6)Cl(5). The direct solution cyclic voltammetry of B(C(6)F(5))(3) has been obtained for the first time and electrochemical measurements upon the entire series B(C(6)F(5))(3-n)(C(6)Cl(5))(n) (n = 0-3) corroborate the spectroscopic data, revealing C(6)Cl(5) to be a more electron

  16. Zn-catalyzed enantio- and diastereoselective formal [4 + 2] cycloaddition involving two electron-deficient partners: asymmetric synthesis of piperidines from 1-azadienes and nitro-alkenes.

    PubMed

    Chu, John C K; Dalton, Derek M; Rovis, Tomislav

    2015-04-08

    We report a catalytic asymmetric synthesis of piperidines through [4 + 2] cycloaddition of 1-azadienes and nitro-alkenes. The reaction uses earth abundant Zn as catalyst and is highly diastereo- and regioselective. A novel BOPA ligand (F-BOPA) confers high reactivity and enantioselectivity in the process. The presence of ortho substitution on the arenes adjacent to the bis(oxazolines) was found to be particularly impactful, due to limiting the undesired coordination of 1-azadiene to the Lewis acid and thus allowing the reaction to be carried out at lower temperature. A series of secondary kinetic isotope effect studies using a range of ligands implicates a stepwise mechanism for the transformation, involving an initial Michael-type addition of the imine to the nitro-alkene followed by a cyclization event. The stepwise mechanism obviates the electronic requirement inherent to a concerted mechanism, explaining the successful cycloaddition between two electron-deficient partners.

  17. 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.

  18. Charge transfer excitations from particle-particle random phase approximation—Opportunities and challenges arising from two-electron deficient systems

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Dominguez, Adriel; Zhang, Du; Lutsker, Vitalij; Niehaus, Thomas A.; Frauenheim, Thomas; Yang, Weitao

    2017-03-01

    The particle-particle random phase approximation (pp-RPA) is a promising method for studying charge transfer (CT) excitations. Through a detailed analysis on two-electron deficient systems, we show that the pp-RPA is always able to recover the long-distance asymptotic -1/R trend for CT excitations as a result of the concerted effect between orbital energies and the pp-RPA kernel. We also provide quantitative results for systems with relatively short donor-acceptor distances. With conventional hybrid or range-separated functionals, the pp-RPA performs much better than time-dependent density functional theory (TDDFT), although it still gives underestimated results which are not as good as TDDFT with system-dependent tuned functionals. For pp-RPA, there remain three great challenges in dealing with CT excitations. First, the delocalized frontier orbitals in strongly correlated systems often lead to difficulty with self-consistent field convergence as well as an incorrect picture with about half an electron transferred. Second, the commonly used density functionals often underestimate the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (LUMO) for the two-electron deficient species, resulting in systems with delocalized orbitals. Third, the performance of pp-RPA greatly depends on the energy difference between the LUMO and a higher virtual orbital. However, the meaning of the orbital energies for higher virtual orbitals is still not clear. We also discuss the performance of an approximate pp-RPA scheme that uses density functional tight binding (pp-DFTB) as reference and demonstrate that the aforementioned challenges can be overcome by adopting suitable range-separated hybrid functionals. The pp-RPA and pp-DFTB are thus promising general approaches for describing charge transfer excitations.

  19. Sticker Bonding.

    ERIC Educational Resources Information Center

    Frazier, Laura Corbin

    2000-01-01

    Introduces a science activity on the bonding of chemical compounds. Assigns students the role of either a cation or anion and asks them to write the ions they may bond with. Assesses students' understanding of charge, bonding, and other concepts. (YDS)

  20. 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

    2010-07-05

    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.

  1. Role of the inner-sphere reorganization in the photoinduced electron transfer reaction of Ru(II) complexes containing imine C=N or Azo N=N double bonds in the ligands

    SciTech Connect

    Maruyama, Mutsuhiro; Kaizu, Youkoh

    1995-04-20

    Photoinduced oxidative and reductive electron transfer (ET) reactions of excited Ru(imin){sub 3}{sup 2+} (imin = 2-(N-methylformimidoyl)pyridine), Ru(imin){sub 2}(CN){sub 2}, and Ru(azpy){sub 3}{sup 2+} (azpy = 2-(phenylazo)pyridine), where imin and azpy contain imine C=N and azo N=N double bonds, respectively, with organic quenchers were investigated in acetonitrile solutions, and their {Delta}G dependencies of the quenching rate constants (k{sub q}) were compared with those of Ru(bpy){sub 3}{sup 2+} (bpy = 2,2`-bipyridine) and Ru(L){sub 2}(CN){sub 2} complexes where L = 4,4`- or 5,5`-dmbpy (dmbpy = dimethyl-2,2`-bipyridine) and phen (phen = 1,10-phenanthroline). The oxidative quenching rate constants of Ru(imin){sub 3}{sup 2+} and Ru(imin){sub 2}(CN){sub 2} are smaller than those of the corresponding bpy, dmbpy, and phen complexes at the same {Delta}G value in the normal region. However, the {Delta}G dependencies of the reductive quenching rate constants of Ru(imin){sub 3}{sup 2+} and Ru(azpy){sub 3}{sup 2+} coincide with that of the corresponding bpy complex. The inner-sphere reorganization ({lambda}{sub in}) caused by the deformation of the C=N bond of imin is considered to be the main reason for the disadvantage of ET in the normal region of the oxidative ET reactions of excited Ru(imin){sub 3}{sup 2+} and Ru(imin){sub 2}(CN){sub 2}. 44 refs., 6 figs., 6 tabs.

  2. Catalysis of Heterocyclic Azadiene Cycloaddition Reactions by Solvent Hydrogen Bonding: Concise Total Synthesis of Methoxatin.

    PubMed

    Glinkerman, Christopher M; Boger, Dale L

    2016-09-28

    Although it has been examined for decades, no general approach to catalysis of the inverse electron demand Diels-Alder reactions of heterocyclic azadienes has been introduced. Typically, additives such as Lewis acids lead to nonproductive consumption of the electron-rich dienophiles without productive activation of the electron-deficient heterocyclic azadienes. Herein, we report the first general method for catalysis of such cycloaddition reactions by using solvent hydrogen bonding of non-nucleophilic perfluoroalcohols, including hexafluoroisopropanol (HFIP) and trifluoroethanol (TFE), to activate the electron-deficient heterocyclic azadienes. Its use in promoting the cycloaddition of 1,2,3-triazine 4 with enamine 3 as the key step of a concise total synthesis of methoxatin is described.

  3. Novel photofunctional multicomponent rare earth (Eu3+, Tb3+, Sm3+ and Dy3+) hybrids with double cross-linking siloxane covalently bonding SiO2/ZnS nanocomposite.

    PubMed

    Yan, Bing; Zhao, Yan; Li, Ya-Juan

    2011-01-01

    Zinc sulfide (ZnS) quantum dot is modified with 3-mercaptopropyltrimethoxysilane (MPTMS) to obtain MPTMS functionalized SiO(2)/ZnS nanocomposite. Novel rare earth/inorganic/organic hybrid materials are prepared by using 3-(triethoxysilyl)-propyl isocyanate (TESPIC) as an organic bridge molecule that can both coordinate to rare earth ions (Eu(3+), Tb(3+), Sm(3+) and Dy(3+)) and form an inorganic Si-O-Si network with SiO(2) ZnS nanocomposite after cohydrolysis and copolycondensation through a sol-gel process. These multicomponent hybrids with double cross-linking siloxane (TESPIC-MPTMS) covalently bonding SiO(2)/ZnS and assistant ligands (Phen = 1,10-phenanthroline, Bipy = 2,2'-bipyridyl) are characterized and especially the photoluminescence properties of them are studied in detail. The luminescent spectra of the hybrids show the dominant excitation of TESPIC-MPTMS-SiO(2)/ZnS unit and the unique emission of rare earth ions, suggesting that TESPIC-MPTMS-SiO(2)/ZnS unit behaves as the main energy donor and effective energy transfer take place between it and rare earth ions. Besides, the luminescent performance of Bipy-RE-TESPIC-MPTM-SiO(2)/ZnS hybrids are superior to that of Phen-RE-TESPIC-MPTMS-SiO(2)/ZnS ones (RE=Eu, Tb, Sm, Dy), which reveals that Bipy or Phen only act as structural ligand within the hybrid systems.

  4. The partial reduction of electron-deficient pyrroles: procedures describing both Birch (Li/NH3) and ammonia-free (Li/DBB) conditions.

    PubMed

    Donohoe, Timothy J; Thomas, Rhian E

    2007-01-01

    The partial reduction of electron-deficient pyrroles using either Birch (Li/NH(3)) or ammonia-free (Li/di-tert-butyl biphenyl) conditions allows formation of pyrroline compounds in good yield and, when combined with a reductive alkylation or similar approach, leads to highly functionalized, synthetically useful compounds. This methodology has been proven in the syntheses of several complex natural products, all of which show interesting biological activity. This protocol describes in detail the following stages of the partial reduction procedure: formation of the reducing solution, partial reduction of the pyrrole compound and finally quench of the resulting anion/dianion using either protonating agents or an aldehyde. The ammonia-free conditions described herein are particularly useful for reactions requiring the use of reactive electrophiles, such as acid chlorides or enolizable aldehydes, which are incompatible with the standard Birch reduction conditions. The reaction procedure for the ammonia Birch reduction (procedure A) takes about 9.5 h to complete. Those described for the ammonia-free reductions, procedure B and procedure C, can be expected to take approximately 33 and 8 h, respectively.

  5. 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

  6. Crystal and molecular structure of W(eta/sup 2/-HC double bond COAlCl/sub 3/)(CO)(PMe/sub 3/)/sub 3/Cl, a product of the coupling of methylidyne and carbonyl ligands on tungsten

    SciTech Connect

    Churchill, M.R.; Wasserman, H.J.

    1983-01-05

    A single-crystal x-ray diffraction analysis has been performed on the title complex, which was prepared by Holmes and Schrock through AlCl/sub 3/-promoted coupling of W(CH)(PMe/sub 3/)/sub 4/Cl with carbon monoxide. The complex crystallizes in the centrosymmetric monoclinic space group P2/sub 1//c with a = 10.420 (2) A, b = 12.896 (2) A, c = 19.319 (4) A, ..beta.. = 105.880 (15)/sup 0/, V = 2497.1 (9) A/sup 3/, rho(calcd) = 1.73 g cm/sup -3/ for Z = 4, and mol wt = 650.0. Automated four-circle diffractometer intensity data (Syntex P2/sub 1/) were used to solve the structure; refinement led to R/sub F/ = 3.2% and R/sub wF/ = 3.0% for all 4423 unique reflections with 4.0/sup 0/ < 2 theta < 50.0/sup 0/ (Mo K..cap alpha.. radiation). The octahedral coordination environment about the central tungsten atom consists of three meridional PMe/sub 3/ ligands, a terminal carbonyl, a chloride, and an eta/sup 2/-HC double bond COAlCl/sub 3/ ligand. The last is oriented parallel to the carbonyl ligand and is best described as a substituted acetylene with an acetylenic carbon-carbon linkage of 1.316 (6) A and short tungsten-carbon distances of 2.034 (4) and 2.009 (5) A. The aluminum-oxygen distance is 1.751 (3) A; this value represents a significantly stronger Al-O interaction than has been observed in other structures containing Al-O (carbonyl; acyl) linkages.

  7. Comparison of thermal lensing effects between single-end and double-end diffusion-bonded Nd:YVO4 crystals for 4F 3/2-->4I 11/2 and 4F 3/2-->4I 13/2 transitions.

    PubMed

    Chang, Y T; Huang, Y P; Su, K W; Chen, Y F

    2008-12-08

    The effective focal lengths of thermal lens in diode-end-pumped continuous-wave Nd:YVO(4) lasers for the (4)F(3/2)-->(4)I(11/2) and (4)F(3/2)-->(4)I(13/2) transitions were determined. The experimental results revealed that the thermal lensing effect for the (4)F(3/2)-->(4)I(11/2) transition can be sufficiently improved by employing a single-end diffusion-bonded Nd:YVO(4) crystal replacing a conventional Nd:YVO(4) crystal. However, using a double-end diffusion-bonded Nd:YVO(4) crystal was a great improvement over a single-end diffusion-bonded Nd:YVO(4) crystal for the (4)F(3/2)-->(4)I(13/2) transition with stronger thermal lensing effect.

  8. 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.

  9. 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.

  10. 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!

  11. 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…

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. Effect of bond thickness on fracture and fatigue strength of adhesively bonded composite joints

    NASA Technical Reports Server (NTRS)

    Mall, S.; Ramamurthy, G.

    1989-01-01

    An experimental investigation of composite to composite bonded joints was undertaken to study the effect of bond thickness on debond growth rate under cyclic loading and critical strain energy release rate under static loading. Double cantilever beam specimens of graphite/epoxy adherends bonded with EC 3445 were tested under mode I loading. A different behavior of fracture and fatigue strength was observed with variation of bondline thickness.

  17. 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)

  18. 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.

  19. Molar efficiency study of chlorinated NPG substitutes in dentin bonding.

    PubMed

    Miniotis, N J; Bennett, P S; Johnston, A D

    1993-06-01

    This study evaluated and compared the contributions to dentin adhesive bonding of three N-phenylglycine analogues with electron-withdrawing substituents on the aromatic ring. These electron-deficient "N-compounds" included: N-(4-chlorophenyl)-glycine (NCPG), N-methyl-N-(4-chlorophenyl)-glycine (NMNCPG), and N-(3,4-dichlorophenyl)-glycine (NDCPG). An experimental three-step dentin-bonding protocol that consisted of sequential application of acidic ferric oxalate solution, an N-compound in acetone, and a surface-active comonomer in acetone was used. The first and third steps were held constant throughout the study. Each N-compound (NCPG, NMNCPG, NDCPG) was used in step two at ten concentrations ranging from 0.0 mol/L (pure acetone) to 5 x 10(-1) mol/L, depending on solubility. After overnight storage in distilled water, the dentin-to-composite bonds were broken in tension. The data were analyzed with ANOVA, and multiple comparisons were performed with Duncan's Multiple Range test. All statistical tests were controlled at alpha = 0.05. At 5 x 10(-3) mol/L, the relative effectiveness of the three N-compounds (as measured by tensile bond strengths) was NMNCPG > NCPG > NDCPG. Of all concentrations studied, the mean bond strengths produced with NMNCPG were statistically as good as or better than those produced by the other two compounds, and NCPG was always as good as or better than NDCPG. Increased electron-withdrawing from the nitrogen of the amine group by the substituents narrowed the effective concentration range for dentin bonding and, in general, produced lower mean bond strengths between dentin and composite.

  20. 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

  1. Marginal adaptation of dentin bonded ceramic inlays: effects of bonding systems and luting resin composites.

    PubMed

    Haller, Bernd; Hässner, Katrin; Moll, Karlheinz

    2003-01-01

    This in vitro study evaluated the marginal adaptation of bonded inlays of lucite-reinforced glass ceramic (Empress) to dentin as influenced by different bonding systems and by luting resin composites (LRCs) with different curing modes. Forty-eight Empress inlays etched with 5% hydrofluoric acid and treated with a silane-coupling agent (Monobond-S) were bonded to two-surface Class II cavities. Two total-etch bonding systems (OptiBond FL, Nexus) and one bonding system with selective enamel etching and a self-conditioning dentin primer (ART Bond) were included in the study. ART Bond was tested with and without the pre-curing of a first layer of adhesive resin selectively applied to the cervical cavity floor (selective double-bond technique). Each bonding system was used in combination with a light-cured resin composite (Prodigy) and a dual-cured LRC (Nexus or Vita Cerec Duo Cement). Marginal integrity was evaluated before and after thermocycling (TC) in a scanning electron microscope (SEM). Dye penetration tests were performed after TC was completed. The median percentages of continuous margin in dentin ranged from 80% to 100% before TC and from 53.5% to 96.1 % after TC. After TC, the influence of the bonding system was more pronounced than that of the LRC. In combination with the LC resin composite, ART Bond with precuring was significantly higher and the Nexus bonding system had significantly lower proportions of continuous margin than all the other bonding systems investigated. Swelling of the adhesive along the gingival margins was frequently found with the Nexus bonding system and with ART Bond without pre-curing. Microleakage was detected with all bonding system/LRC combinations, with somewhat lower rates in specimens completed using the selective double-bond technique. With the exception of the Nexus bonding system, post-TC marginal integrity was not influenced by the curing mode of the LRC (LC vs DC). In conclusion, the marginal quality of dentin bonded

  2. 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.

  3. 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.

  4. Towards ideal synthesis: alkenylation of aryl C-H bonds by a Fujiwara-Moritani reaction.

    PubMed

    Zhou, Lihong; Lu, Wenjun

    2014-01-13

    An overview of recent progress in the Fujiwara-Moritani reaction, which is the palladium-catalyzed oxidative coupling of arenes with olefins to afford alkenyl arenes, is described. It is emphasized that regioselectivity on aryl ortho- or meta-CH activation could be controlled very well in the presence of Pd, Rh, or Ru catalysts with the assistance of various chelation groups on aromatic rings in this coupling reaction. Catalytic alkenylation of aryl CH bonds from simple arenes is also discussed, especially from electron-deficient arenes. These advanced protocols would not only make the Fujiwara-Moritani reaction more useful and applicable in organic synthesis but also light the way for the further development of the functionalization of normal CH bonds.

  5. 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)

  6. 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…

  7. Cycloaddition reaction of 2-azadienes derived from beta-amino acids with electron-rich and electron-deficient alkenes and carbonyl compounds. Synthesis of pyridine and 1,3-oxazine derivatives.

    PubMed

    Palacios, Francisco; Herrán, Esther; Rubiales, Gloria; Ezpeleta, Jose María

    2002-04-05

    Functionalized keto-enamines 6 were obtained by nucleophilic addition of enol ethers to the imine moiety of 2-azadienes derived from dehydroaspartic esters 4. Reactions of 2-azadiene 4c containing three electron-withdrawing substituents (CO(2)R) with enol ethers 5 in the presence of lithium perchlorate led to the formation of tetrahydropyridine derivatives 7 in a regio- and stereoselective fashion. 2H-[1,3]-oxazines 10 and pyridine derivatives 12 and 13 were obtained by heterocycloaddition reactions of electron-poor azadienes 4d-g containing two electron-withdrawing substituents (4-O(2)N-C(6)H(4), CO(2)R) in positions 1 and 4 with carbonyl derivatives (ethyl glyoxalate 9a and diethyl ketomalonate 9b) and the electron-deficient olefin tetracyanoethylene 11.

  8. 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

  9. 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.

  10. 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.

  11. A double mutation of Escherichia coli 2C-methyl-d-erythritol-2,4-cyclodiphosphate synthase disrupts six hydrogen bonds with, yet fails to prevent binding of, an isoprenoid diphosphate

    PubMed Central

    Sgraja, Tanja; Kemp, Lauris E.; Ramsden, Nicola; Hunter, William N.

    2005-01-01

    The essential enzyme 2C-methyl-d-erythritol-2,4-cyclodiphosphate (MECP) synthase, found in most eubacteria and the apicomplexan parasites, participates in isoprenoid-precursor biosynthesis and is a validated target for the development of broad-spectrum antimicrobial drugs. The structure and mechanism of the enzyme have been elucidated and the recent exciting finding that the enzyme actually binds diphosphate-containing isoprenoids at the interface formed by the three subunits that constitute the active protein suggests the possibility of feedback regulation of MECP synthase. To investigate such a possibility, a form of the enzyme was sought that did not bind these ligands but which would retain the quaternary structure necessary to create the active site. Two amino acids, Arg142 and Glu144, in Escherichia coli MECP synthase were identified as contributing to ligand binding. Glu144 interacts directly with Arg142 and positions the basic residue to form two hydrogen bonds with the terminal phosphate group of the isoprenoid diphosphate ligand. This association occurs at the trimer interface and three of these arginines interact with the ligand phosphate group. A dual mutation was designed (Arg142 to methionine and Glu144 to leucine) to disrupt the electrostatic attractions between the enzyme and the phosphate group to investigate whether an enzyme without isoprenoid diphosphate could be obtained. A low-resolution crystal structure of the mutated MECP synthase Met142/Leu144 revealed that geranyl diphosphate was retained despite the removal of six hydrogen bonds normally formed with the enzyme. This indicates that these two hydrophilic residues on the surface of the enzyme are not major determinants of isoprenoid binding at the trimer interface but rather that hydrophobic interactions between the hydrocarbon tail and the core of the enzyme trimer dominate ligand binding. PMID:16511114

  12. [Double responses].

    PubMed

    Motté, G; Dinanian, S; Sebag, C; Drieu, L; Slama, M

    1995-12-01

    Double response is a rare electrocardiographic phenomenon requiring two atrioventricular conduction pathways with very different electrophysiological properties. Double ventricular responses are the usual manifestation: an atrial depolarisation (spontaneous or provoked, anticipated or not) is followed by a first ventricular response dependent on an accessory pathway or a rapid nodal pathway and then a second response resulting from sufficiently delayed transmission through a nodal pathway for the ventricles to have recovered their excitability when the second wave of activation reaches them. A simple curiosity when isolated and occurring under unusual conditions, particularly during electrophysiological investigation of the Wolff-Parkinson-White syndrome, the double response may initiate symptomatic non-reentrant junctional tachycardia when associated with nodal duality and repeating from atria in sinus rhythm. The functional incapacity and resistance to antiarrhythmic therapy may require referral for ablation of the slow pathway.

  13. 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.

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

    PubMed

    Cuthbertson, James D; MacMillan, David W C

    2015-03-05

    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.

  15. 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.

  16. Measurement of bonding energy in an anhydrous nitrogen atmosphere and its application to silicon direct bonding technology

    NASA Astrophysics Data System (ADS)

    Fournel, F.; Continni, L.; Morales, C.; Da Fonseca, J.; Moriceau, H.; Rieutord, F.; Barthelemy, A.; Radu, I.

    2012-05-01

    Bonding energy represents an important parameter for direct bonding applications as well as for the elaboration of physical mechanisms at bonding interfaces. Measurement of bonding energy using double cantilever beam (DCB) under prescribed displacement is the most used technique thanks to its simplicity. The measurements are typically done in standard atmosphere with relative humidity above 30%. Therefore, the obtained bonding energies are strongly impacted by the water stress corrosion at the bonding interfaces. This paper presents measurements of bonding energies of directly bonded silicon wafers under anhydrous nitrogen conditions in order to prevent the water stress corrosion effect. It is shown that the measurements under anhydrous nitrogen conditions (less than 0.2 ppm of water in nitrogen) lead to high stable debonding lengths under static load and to higher bonding energies compared to the values measured under standard ambient conditions. Moreover, the bonding energies of Si/SiO2 or SiO2/SiO2 bonding interfaces are measured overall the classical post bond annealing temperature range. These new results allow to revisit the reported bonding mechanisms and to highlight physical and chemical phenomena in the absence of stress corrosion effect.

  17. 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.

  18. Double screening

    SciTech Connect

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

    2016-06-15

    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.

  19. AFOSR Wafer Bonding

    DTIC Science & Technology

    2009-07-31

    cleanliness (foreign particles) and surface morphology (roughness). Two silicon wafers, when properly cleaned, can easily bond at room temperature because of...4 Figure IV data for nSi-nGaN bond. Structure is similar to that shown in Figure Difficulties and Knowledge Added Surface Morphology and...Particles One of the most important features of materials in determining whether they will bond is the quality of the bonding surfaces , in both

  20. 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.

  1. Acrylic mechanical bond tests

    SciTech Connect

    Wouters, J.M.; Doe, P.J.

    1991-02-01

    The tensile strength of bonded acrylic is tested as a function of bond joint thickness. 0.125 in. thick bond joints were found to posses the maximum strength while the acceptable range of joints varied from 0.063 in. to almost 0.25 in. Such joints are used in the Sudbury Neutrino Observatory.

  2. 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.

  3. Bonding aluminum beam leads

    NASA Technical Reports Server (NTRS)

    Burkett, F. S.

    1978-01-01

    Report makes it relatively easy for hybrid-circuit manufacturers to convert integrated circuit chips with aluminum bead leads. Report covers: techniques for handling tiny chips; proper geometries for ultrasonic bonding tips; best combinations of pressure, pulse time, and ultrasonic energy for bonding; and best thickness for metal films to which beam leads are bonded.

  4. 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.

  5. 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 Central

    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

  6. 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.

  7. The effect of sulfur covalent bonding on the electronic shells of silver clusters.

    PubMed

    Pedicini, Anthony F; Reber, Arthur C; Khanna, Shiv N

    2013-10-28

    The nature of the bonding in Ag(n)S(m)(0∕-) clusters, n = 1-7; m = 1-4, has been analyzed to understand its effect on the electronic shell structure of silver clusters. First-principle investigations reveal that the sulfur atoms prefer 2 or 3-coordinate sites around a silver core, and that the addition of sulfur makes the planar structures compact. Molecular orbital analysis finds that the 3p orbitals of sulfur form a bonding orbital and two weakly bonding lone pairs with silver. We examine the electronic shell structures of Ag6Sm, which are two electrons deficient of a spherical closed electronic shell prior to the addition of sulfur, and Ag7S(m)(-) clusters that contain closed electronic shells prior to the addition of sulfur. The Ag6S4 cluster has a distorted octahedral silver core and an open shell with a multiplicity of 3, while the Ag7S(n_(-) clusters have compact geometries with enhanced stability, confirming that the clusters maintain their electronic shell structure after bonding with sulfur.

  8. 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.

  9. Hydrogen multicentre bonds.

    PubMed

    Janotti, Anderson; Van de Walle, Chris G

    2007-01-01

    The concept of a chemical bond stands out as a major development in the process of understanding how atoms are held together in molecules and solids. Lewis' classical picture of chemical bonds as shared-electron pairs evolved to the quantum-mechanical valence-bond and molecular-orbital theories, and the classification of molecules and solids in terms of their bonding type: covalent, ionic, van der Waals and metallic. Along with the more complex hydrogen bonds and three-centre bonds, they form a paradigm within which the structure of almost all molecules and solids can be understood. Here, we present evidence for hydrogen multicentre bonds-a generalization of three-centre bonds-in which a hydrogen atom equally bonds to four or more other atoms. When substituting for oxygen in metal oxides, hydrogen bonds equally to all the surrounding metal atoms, becoming fourfold coordinated in ZnO, and sixfold coordinated in MgO. These multicentre bonds are remarkably strong despite their large hydrogen-metal distances. The calculated local vibration mode frequency in MgO agrees with infrared spectroscopy measurements. Multicoordinated hydrogen also explains the dependence of electrical conductivity on oxygen partial pressure, resolving a long-standing controversy on the role of point defects in unintentional n-type conductivity of ZnO (refs 8-10).

  10. σ-Bond Prevents Short π-Bonds: A Detailed Theoretical Study on the Compounds of Main Group and Transition Metal Complexes

    NASA Astrophysics Data System (ADS)

    Pathak, Biswarup; Umayal, Muthaiah; Jemmis, Eluvathingal D.

    The unusual shortness of the bond length in several main group and transition metal compounds is explained on the basis of their π-alone bonding. The detailed electronic structure calculation on C2, HBBH, and Fe2(CO)6 shows that each of them has two π-alone bonds (unsupported by an underlying σ-bond), whereas B2 has two-half π-bonds. The C-C bond length in C2 is 1.240 Å, shorter than any C-C double (σ + π, in C2H4, C-C=1.338 Å) bonded species. The B-B bond distance in B2 (1.590 Å, two half-π bonds) is shorter than any B-B single σ-bonded (~1.706 Å) species. The calculated Fe-Fe bond distance of 2.002 Å in Fe2(CO)6 is shorter than those of some experimentally known M-M single bonded compounds in the range of 2.904-3.228 Å. Here, our detailed studies on the second and third row diatomics (five, six, seven and eight valence electrons species) and transition metal complexes show that π-alone bonds left to themselves are shorter than σ-bonds; in many ways, σ-bonds prevent π-bonds from adopting their optimal shorter distances.

  11. Sulfide bonded atomic radii

    NASA Astrophysics Data System (ADS)

    Gibbs, G. V.; Ross, N. L.; Cox, D. F.

    2017-03-01

    The bonded radius, r b(S), of the S atom, calculated for first- and second-row non-transition metal sulfide crystals and third-row transition metal sulfide molecules and crystals indicates that the radius of the sulfur atom is not fixed as traditionally assumed, but that it decreases systematically along the bond paths of the bonded atoms with decreasing bond length as observed in an earlier study of the bonded radius of the oxygen atom. When bonded to non-transition metal atoms, r b(S) decreases systematically with decreasing bond length from 1.68 Å when the S atom is bonded to the electropositive VINa atom to 1.25 Å when bonded to the more electronegative IVP atom. In the case of transition metal atoms, rb(S) likewise decreases with decreasing bond length from 1.82 Å when bonded to Cu and to 1.12 Å when bonded to Fe. As r b(S) is not fixed at a given value but varies substantially depending on the bond length and the field strength of the bonded atoms, it is apparent that sets of crystal and atomic sulfide atomic radii based on an assumed fixed radius for the sulfur atom are satisfactory in that they reproduce bond lengths, on the one hand, whereas on the other, they are unsatisfactory in that they fail to define the actual sizes of the bonded atoms determined in terms of the minima in the electron density between the atoms. As such, we urge that the crystal chemistry and the properties of sulfides be studied in terms of the bond lengths determined by adding the radii of either the atomic and crystal radii of the atoms but not in terms of existing sets of crystal and atomic radii. After all, the bond lengths were used to determine the radii that were experimentally determined, whereas the individual radii were determined on the basis of an assumed radius for the sulfur atom.

  12. An electron-deficient porphyrin tape.

    PubMed

    Mori, Hirotaka; Tanaka, Takayuki; Aratani, Naoki; Lee, Byung Sun; Kim, Pyosang; Kim, Dongho; Osuka, Atsuhiro

    2012-08-01

    Hexakis(pentafluorophenyl)-substituted meso-meso-linked Zn(II)-diporphyrin (9), which was prepared by the acid-catalyzed cross-condensation of 1,1,2,2-tetrapyrroethane (5) with dipyrromethane dicarbinol (6), was converted into meso-meso,β-β,β-β triply linked Zn(II)-diporphyrin 3 by oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and Sc(OTf)(3). Beside the red-shifted absorption spectrum and split first oxidation potential that are common to the triply-linked Zn(II)-diporphyrins, diporphyrin 3 exhibited considerably improved chemical stability owing to a lowered HOMO and good solubility in common organic solvents. The two-photon absorption (TPA) cross-section and S(1)-state lifetime of compound 3 were 1700 GM and 3.3 ps, respectively.

  13. Competitive pi interactions and hydrogen bonding within imidazolium ionic liquids.

    PubMed

    Matthews, Richard P; Welton, Tom; Hunt, Patricia A

    2014-02-21

    In this paper we have explored the structural and energetic landscape of potential π(+)-π(+) stacked motifs, hydrogen-bonding arrangements and anion-π(+) interactions for gas-phase ion pair (IP) conformers and IP-dimers of 1,3-dimethylimidazolium chloride, [C1C1im]Cl. We classify cation-cation ring stacking as an electron deficient π(+)-π(+) interaction, and a competitive anion on-top IP motif as an anion-donor π(+)-acceptor interaction. 21 stable IP-dimers have been obtained within an energy range of 0-126 kJ mol(-1). The structures have been found to exhibit a complex interplay of structural features. We have found that low energy IP-dimers are not necessarily formed from the lowest energy IP conformers. The sampled range of IP-dimers exhibits new structural forms that cannot be recovered by examining the ion-pairs alone, moreover the IP-dimers are recovering additional key features of the local liquid structure. Including dispersion is shown to impact both the relative energy ordering and the geometry of the IPs and IP-dimers, however the impact is found to be subtle and dependent on the underlying functional.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Kinetic solvent effects on the reactions of the cumyloxyl radical with tertiary amides. Control over the hydrogen atom transfer reactivity and selectivity through solvent polarity and hydrogen bonding.

    PubMed

    Salamone, Michela; Mangiacapra, Livia; Bietti, Massimo

    2015-01-16

    A laser flash photolysis study on the role of solvent effects on hydrogen atom transfer (HAT) from the C-H bonds of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-formylpyrrolidine (FPRD), and N-acetylpyrrolidine (APRD) to the cumyloxyl radical (CumO(•)) was carried out. From large to very large increases in the HAT rate constant (kH) were measured on going from MeOH and TFE to isooctane (kH(isooctane)/kH(MeOH) = 5-12; kH(isooctane)/kH(TFE) > 80). This behavior was explained in terms of the increase in the extent of charge separation in the amides determined by polar solvents through solvent-amide dipole-dipole interactions and hydrogen bonding, where the latter interactions appear to play a major role with strong HBD solvents such as TFE. These interactions increase the electron deficiency of the amide C-H bonds, deactivating these bonds toward HAT to an electrophilic radical such as CumO(•), indicating that changes in solvent polarity and hydrogen bonding can provide a convenient method for deactivation of the C-H bond of amides toward HAT. With DMF, a solvent-induced change in HAT selectivity was observed, suggesting that solvent effects can be successfully employed to control the reaction selectivity in HAT-based procedures for the functionalization of C-H bonds.

  19. Mother-Child Bonding.

    ERIC Educational Resources Information Center

    Pearce, Joseph Chilton

    1994-01-01

    Examines the nature of mother-child bonding from the prenatal stage through early infancy, discussing how the mother's actions, even before birth, stimulate her child's senses. Explains the crucial role that physical contact, breastfeeding, and visual stimuli have on mother-child bonding in human and animal newborns. (MDM)

  20. 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.

  1. 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)

  2. Tetrel Bonding Interactions.

    PubMed

    Bauzá, Antonio; Mooibroek, Tiddo J; Frontera, Antonio

    2016-02-01

    Tetrel (Tr) bonding is first placed into perspective as a σ-hole bonding interaction with atoms of the Tr family. An sp(3) R4Tr unit has four σ-holes with which a Lewis base can form a complex. We then highlight some inspiring crystal structures where Tr bonding is obvious, followed by an account of our own work. We have shown that Tr bonding is ubiquitous in the solid state and we have highlighted that Tr bonding with carbon is possible when C is placed in the appropriate chemical context. We hope that this account serves as an initial guide and source of inspiration for others wishing to exploit this vastly underexplored interaction.

  3. 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.

  4. 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.

  5. 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.

  6. Double Your Major, Double Your Return?

    ERIC Educational Resources Information Center

    Del Rossi, Alison F.; Hersch, Joni

    2008-01-01

    We use the 2003 National Survey of College Graduates to provide the first estimates of the effect on earnings of having a double major. Overall, double majoring increases earnings by 2.3% relative to having a single major among college graduates without graduate degrees. Most of the gains from having a double major come from choosing fields across…

  7. Disulfide Bond Requirements for Active Wnt Ligands*

    PubMed Central

    MacDonald, Bryan T.; Hien, Annie; Zhang, Xinjun; Iranloye, Oladoyin; Virshup, David M.; Waterman, Marian L.; He, Xi

    2014-01-01

    Secreted Wnt lipoproteins are cysteine-rich and lipid-modified morphogens that bind to the Frizzled (FZD) receptor and LDL receptor-related protein 6 (LRP6). Wnt engages FZD through protruding thumb and index finger domains, which are each assembled from paired β strands secured by disulfide bonds and grasp two sides of the FZD ectodomain. The importance of Wnt disulfide bonds has been assumed but uncharacterized. We systematically analyzed cysteines and associated disulfide bonds in the prototypic Wnt3a. Our data show that mutation of any individual cysteine of Wnt3a results in covalent Wnt oligomers through ectopic intermolecular disulfide bond formation and diminishes/abolishes Wnt signaling. Although individual cysteine mutations in the amino part of the saposin-like domain and in the base of the index finger are better tolerated and permit residual Wnt3a secretion/activity, those in the amino terminus, the thumb, and at the tip of the index finger are incompatible with secretion and/or activity. A few select double cysteine mutants based on the disulfide bond pattern restore Wnt secretion/activity. Further, a double cysteine mutation at the index finger tip results in a Wnt3a with normal secretion but minimal FZD binding and dominant negative properties. Our results experimentally validate predictions from the Wnt crystal structure and highlight critical but different roles of the saposin-like and cytokine-like domains, including the thumb and the index finger in Wnt folding/secretion and FZD binding. Finally, we modified existing expression vectors for 19 epitope-tagged human WNT proteins by removal of a tag-supplied ectopic cysteine, thereby generating tagged WNT ligands active in canonical and non-canonical signaling. PMID:24841207

  8. 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.

  9. 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

  10. Effect of adhesive layers on microshear bond strength of nanocomposite resin to dentin

    PubMed Central

    Ebrahim, Mohamed I.

    2017-01-01

    Background Bond strength of adhesive layer can absorb unwanted stresses of polymerization shrinkage in composite resin restorations; increased microshear bond strength can prevent failure of restoration materials, the purpose of this study was to evaluate the effect of adhesive layers on microshear bond strength of nanocomposite resin to dentin. Material and Methods Two different types of adhesive systems: universal adhesive (ExciTE) and newly developed adhesive (Nano-Bond), and one type of light-cured resin restorative material (Nanocomposite resin) were used in this study. The occlusal surfaces of extracted human molar teeth were ground perpendicular to the long axis of each tooth to expose a flat dentin surface. The adhesives were applied on dentin surfaces (single application or double application). Nanocomposite resin was then placed and light cured for 40 seconds. After 24 hours of immersion in water at 37°C, then subjected to thermocycling before testing, a microshear bond test was carried out. The data were analyzed by a two-way ANOVA. For comparison between groups, Tukey’s post-hoc test was used. Results The mean bond strengths of ExciTE and Nano-Bond adhesives with a single application were 8.8 and 16.6 MPa, respectively. The mean bond strengths of ExciTE and Nano-Bond adhesives with double application were 13.2 and 21.8MPa, respectively. There were no statistically significant differences in microshear bond strengths between the single application of Nano-Bond and the double application of ExciTE adhesives. Conclusions Microshear bond strength increased significantly as the applied adhesive layer was doubled. Key words:Adhesive, microshear, bond, strength, nanocomposite. PMID:28210433

  11. 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.

  12. Aspects of glycosidic bond formation in aqueous solution: chemical bonding and the role of water.

    PubMed

    Stubbs, John M; Marx, Dominik

    2005-04-22

    A model of the specific acid-catalyzed glycosidic bond formation in liquid water at ambient conditions is studied based on constrained Car-Parrinello ab initio molecular dynamics. Specifically the reaction of alpha-D-glucopyranose and methanol is found to proceed by a D(N)A(N) mechanism. The D(N) step consists of a concerted protonation of the O(1) hydroxyl leaving group; this process results in the breaking of the C(1)-O(1) bond, and oxocarbenium ion formation involving C(1)=O(5). The second step, A(N), is the formation of the C(1)-O(m) glycosidic bond, deprotonation of the methanol hydroxyl group O(m)H(m), and re-formation of the C(1)-O(5) single bond. A focus of this study is the analysis of the electronic structure during this condensed phase reaction relying on both Boys/Wannier localized orbitals and the electron localization function ELF. This analysis allows the clear elucidation of the chemical bonding features of the intermediate bracketed by the D(N) and A(N) steps, which is a non-solvent equilibrated oxocarbenium cation. Most interestingly, it is found that the oxygen in the pyranose ring becomes "desolvated" upon double bond/oxocarbenium formation, whereas it is engaged in the hydrogen-bonded water network before and after this period. This demonstrates that hydrogen bonding and thus the aqueous solvent play an active role in this reaction implying that microsolvation studies in the gas phase, both theoretical and experimental, might lead to qualitatively different reaction mechanisms compared to solution.

  13. 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.

  14. C-C bond-forming desulfurizations of sulfoximines.

    PubMed

    Reggelin, M; Slavik, S; Bühle, P

    2008-09-18

    Highly substituted, enantiomerically pure azaheterocyclic ring systems play an important role in medicinal chemistry as potential peptide mimetics. Metalated 2-alkenyl sulfoximines offer an efficient entry to this class of compounds. In this paper, we describe a new means to remove the sulfonimidoyl auxiliary with concomitant formation of a C-C double bond.

  15. 30 CFR 281.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF... SHELF Financial Considerations § 281.33 Bonds and bonding requirements. (a) When the leasing...

  16. 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... Bonds and bonding requirements. (a) When the leasing notice specifies that payment of a portion of...

  17. 27 CFR 24.147 - Operations bond or unit bond.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... BUREAU, DEPARTMENT OF THE TREASURY LIQUORS WINE Establishment and Operations Bonds and Consents of Surety § 24.147 Operations bond or unit bond. Notwithstanding the provisions of § 24.146, each person intending to commence or to continue business as the proprietor of a bonded wine premises with an...

  18. The single donator-single acceptor hydrogen bonding structure in water probed by Raman spectroscopy.

    PubMed

    Sun, Qiang

    2010-02-07

    In this work, the Raman spectra of aqueous C(12)E(5) solutions are recorded and utilized to demonstrate the existence of single donator-single acceptor (DA) hydrogen bonding in water. From Raman OH stretching bands of aqueous C(12)E(5) solutions, the relative intensity of 3430 cm(-1) subband increases with C(12)E(5) concentrations. For confined water, the DA hydrogen bonding can be expected to be the important hydrogen bonding species. Therefore, the 3430 cm(-1) component can be ascribed to OH vibration engaged in DA hydrogen bonding. This is in agreement with our recent explanation on Raman OH stretching band of water. For water at ambient conditions, the double donor-double acceptor (DDAA) and DA should be the dominant hydrogen bonding species, the ratio of DDAA to DA can be approximately to be 0.75:1, and the mean hydrogen bonding can be determined to be 2.75.

  19. The single donator-single acceptor hydrogen bonding structure in water probed by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Qiang

    2010-02-01

    In this work, the Raman spectra of aqueous C12E5 solutions are recorded and utilized to demonstrate the existence of single donator-single acceptor (DA) hydrogen bonding in water. From Raman OH stretching bands of aqueous C12E5 solutions, the relative intensity of 3430 cm-1 subband increases with C12E5 concentrations. For confined water, the DA hydrogen bonding can be expected to be the important hydrogen bonding species. Therefore, the 3430 cm-1 component can be ascribed to OH vibration engaged in DA hydrogen bonding. This is in agreement with our recent explanation on Raman OH stretching band of water. For water at ambient conditions, the double donor-double acceptor (DDAA) and DA should be the dominant hydrogen bonding species, the ratio of DDAA to DA can be approximately to be 0.75:1, and the mean hydrogen bonding can be determined to be 2.75.

  20. 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.

  1. Fundamentals of fiber bonding in thermally point-bonded nonwovens

    NASA Astrophysics Data System (ADS)

    Chidambaram, Aparna

    Thermal point bonding (TPB) uses heat and pressure to bond a web of fibers at discrete points imparting strength to the manufactured fabric. This process significantly reduces the strength and elongation of the bridging fibers between bond points while strengthening the web. Single fiber experiments were performed with four structurally different polypropylene fibers to analyze the inter-relationships between fiber structure, fiber properties and bonding process. Two fiber types had a low birefringence sheath or surface layer while the remaining had uniform birefringence profiles through their thickness. Bonds were formed between isolated pairs of fibers by subjecting the fibers to a calendering process and simulating TPB process conditions. The dependence of bond strength on bonding temperature and on the type of fiber used was evaluated. Fiber strengths before and after bonding were measured and compared to understand the effect of bonding on fiber strength. Additionally, bonded fiber strength was compared to the strength of single fibers which had experienced the same process conditions as the bonded pairs. This comparison estimated the effect of mechanical damage from pressing fibers together with steel rolls while creating bonds in TPB. Interfiber bond strength increased with bonding temperature for all fiber types. Fiber strength decreased with increasing bonding temperature for all fiber types except for one type of low birefringent sheath fibers. Fiber strength degradation was unavoidable at temperatures required for successful bonding. Mechanical damage from compression of fibers between rolls was an insignificant factor in this strength loss. Thermal damage during bonding was the sole significant contributor to fiber strength degradation. Fibers with low birefringence skins formed strong bonds with minimal fiber strength loss and were superior to fibers without such surface layers in TPB performance. A simple model to predict the behavior of a two-bond

  2. 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

  3. 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.

  4. Vibrational states and optical transitions in hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Johannsen, P. G.

    1998-03-01

    Proton energies in hydrogen bonds are mostly calculated using a double Morse potential (the DMP model). This form, however, does not reproduce the experimentally observed correlation between the proton stretching frequency and the bond length in an extended bond-length region sufficiently well. An alternative potential is proposed in the present paper. The quantum states of this non-symmetric double-well potential are calculated numerically using the Numerov (Fox-Goodwin) algorithm. It is shown that the optical spectra of hydrogen bonds in various substances can be well approximated on the basis of the transition frequencies and intensities predicted by the present model. For weakly interacting OH impurities in 0953-8984/10/10/008/img1, the overtone spectrum and line intensities are well reproduced, whereas the line broadenings and the decrease of the fundamental stretching frequencies in intermediate and strong hydrogen bonds are traced back to the influence of the reduced height of the central barrier. The model is also extrapolated to the range of symmetric hydrogen bonds, and the calculated transition frequencies are discussed with respect to most recent infra-red experiments on ice under strong compression. A possible artificial infra-red signal from strained diamond anvils is thereby noted.

  5. Nucleation-dependant chemical bonding paradigm: the effect of rare earth ions on the nucleation of urea in aqueous solution.

    PubMed

    Chen, Xiaoyan; Sun, Congting; Wu, Sixin; Xue, Dongfeng

    2017-03-29

    Rare earth ions can be used to construct a variety of novel structures and are favorable to chemical bonding regulation and design. In this study, the chemical bonding paradigm between rare earth ions (Ln(3+)) and urea molecules in an aqueous solution can be tracked by the evolution of C[double bond, length as m-dash]O, NH2, and CN vibration bands during the urea nucleation stage. Rare earth ions such as La(3+), Gd(3+), and Lu(3+) can manipulate the nucleation time of urea via regulating the nucleation-dependant N-C[double bond, length as m-dash]OH-N hydrogen-bonding between urea molecules. Two types of chemical bondings between Ln(3+) and urea molecules have been confirmed, which are Ln(3+)O[double bond, length as m-dash]C-N and Ln(3+)NH2-C. Compared with Ln(3+)NH2-C, Ln(3+) prefers to coordinate with the O[double bond, length as m-dash]C bond in urea. With a higher concentration of rare earth ions in the solution, some N-C[double bond, length as m-dash]OH-N hydrogen bonds are broken as a consequence of the incorporation of Ln(3+) into the lattice, resulting in the decreased symmetry of local urea molecules in the crystalline nuclei and the consequent Ln(3+) concentration-dependent nucleation time of urea. Moreover, using the ionic electronegativity scale of Ln(3+), the different effects of La(3+), Gd(3+), and Lu(3+) on urea nucleation can be further distinguished. The present study provides basic data for unrevealing the chemical bonding regulation role of rare earth ions in the formation of hydrogen bonded materials, which may give insight into the design and fabrication of novel materials utilizing rare earth ions to adjust the chemical bonding process.

  6. 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.

  7. Biomolecular halogen bonds.

    PubMed

    Ho, P Shing

    2015-01-01

    Halogens are atypical elements in biology, but are common as substituents in ligands, including thyroid hormones and inhibitors, which bind specifically to proteins and nucleic acids. The short-range, stabilizing interactions of halogens - now seen as relatively common in biology - conform generally to halogen bonds characterized in small molecule systems and as described by the σ-hole model. The unique properties of biomolecular halogen bonds (BXBs), particularly in their geometric and energetic relationship to classic hydrogen bonds, make them potentially powerful tools for inhibitor design and molecular engineering. This chapter reviews the current research on BXBs, focusing on experimental studies on their structure-energy relationships, how these studies inform the development of computational methods to model BXBs, and considers how BXBs can be applied to the rational design of more effective inhibitors against therapeutic targets and of new biological-based materials.

  8. Metallic-like bonding in plasma-born silicon nanocrystals for nanoscale bandgap engineering.

    PubMed

    Vach, Holger; Ivanova, Lena V; Timerghazin, Qadir K; Jardali, Fatme; Le, Ha-Linh Thi

    2016-10-27

    Based on ab initio molecular dynamics simulations, we show that small nanoclusters of about 1 nm size spontaneously generated in a low-temperature silane plasma do not possess tetrahedral structures, but are ultrastable. Apparently small differences in the cluster structure result in substantial modifications in their electric, magnetic, and optical properties, without the need for any dopants. Their non-tetrahedral geometries notably lead to electron deficient bonds that introduce efficient electron delocalization that strongly resembles the one of a homogeneous electron gas leading to metallic-like bonding within a semiconductor nanocrystal. As a result, pure hydrogenated silicon clusters that form by self-assembly in a plasma reactor possess optical gaps covering most of the solar spectrum from 1.0 eV to 5.2 eV depending simply on their structure and, in turn, on their degree of electron delocalization. This feature makes them ideal candidates for future bandgap engineering not only for photovoltaics, but also for many nano-electronic devices employing nothing else but silicon and hydrogen atoms.

  9. Cooperativity in beryllium bonds.

    PubMed

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

    2014-03-07

    A theoretical study of the beryllium bonded clusters of the (iminomethyl)beryllium hydride and (iminomethyl)beryllium fluoride [HC(BeX)=NH, X = H, F] molecules has been carried out at the B3LYP/6-311++G(3df,2p) level of theory. Linear and cyclic clusters have been characterized up to the decamer. The geometric, energetic, electronic and NMR properties of the clusters clearly indicate positive cooperativity. The evolution of the molecular properties, as the size of the cluster increases, is similar to those reported in polymers held together by hydrogen bonds.

  10. Cast Aluminum Bonding Study

    DTIC Science & Technology

    1988-05-01

    fabricated using P?-’r;est11 bur)ld II19 te(hnll I Oly with 6 cIsL nqs. The cast a lumi num alloy used was A357 . The sur- face preparation was phosphoric acid...from a cast aluminum alloy designated A357 . The bonding surfaces of the adherends were prepared using PAA. One primer and two adhesives considered...System, Cast Aluminum Lap Shear 18 11 Bond Area of 350°F Adhesive System, Cast Aluminum Lap Shear 19 vi LIST OF TABLES TABLE PAGE 1 A357 Chemical

  11. 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.

  12. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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...

  13. 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...

  14. 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.

  15. Bonding with the Past.

    ERIC Educational Resources Information Center

    Common Ground: Archeology and Ethnography in the Public Interest, 1998

    1998-01-01

    An interview with Linda Mayro, archaeologist and cultural resources manager for Pima County, Arizona, discusses efforts of local groups to preserve local Native-American and Mexican cultural-heritage sites in oppositon to commercial land developers. A public information campaign led to passage of a $6.4 million historic preservation bond. (SAS)

  16. 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)

  17. Bonding with Your Baby

    MedlinePlus

    ... can take nearly all of your attention and energy — especially for a breastfeeding mom. Bonding will be much easier if you aren't exhausted by all of the other things going on at home, such as housework, meals, and laundry. It's helpful ...

  18. Photochemical tissue bonding

    DOEpatents

    Redmond, Robert W [Brookline, MA; Kochevar, Irene E [Charlestown, MA

    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.

  19. 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)

  20. [A double gallbladder].

    PubMed

    Mink van der Molen, A B; Salu, M K

    1991-04-06

    A 59-year-old woman is described with symptomatic cholelithiasis. A double gallbladder was incidentally found during abdominal surgery. The literature on a double gallbladder is reviewed with respect to incidence, anatomy, diagnosis and therapy.

  1. 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.

  2. The double identity of linguistic doubling.

    PubMed

    Berent, Iris; Bat-El, Outi; Brentari, Diane; Dupuis, Amanda; Vaknin-Nusbaum, Vered

    2016-11-29

    Does knowledge of language consist of abstract principles, or is it fully embodied in the sensorimotor system? To address this question, we investigate the double identity of doubling (e.g., slaflaf, or generally, XX; where X stands for a phonological constituent). Across languages, doubling is known to elicit conflicting preferences at different levels of linguistic analysis (phonology vs. morphology). Here, we show that these preferences are active in the brains of individual speakers, and they are demonstrably distinct from sensorimotor pressures. We first demonstrate that doubling in novel English words elicits divergent percepts: Viewed as meaningless (phonological) forms, doubling is disliked (e.g., slaflaf < slafmak), but once doubling in form is systematically linked to meaning (e.g., slaf = ball, slaflaf = balls), the doubling aversion shifts into a reliable (morphological) preference. We next show that sign-naive speakers spontaneously project these principles to novel signs in American Sign Language, and their capacity to do so depends on the structure of their spoken language (English vs. Hebrew). These results demonstrate that linguistic preferences doubly dissociate from sensorimotor demands: A single stimulus can elicit diverse percepts, yet these percepts are invariant across stimulus modality--for speech and signs. These conclusions are in line with the possibility that some linguistic principles are abstract, and they apply broadly across language modality.

  3. Double photoionization of halogenated benzene

    SciTech Connect

    AlKhaldi, Mashaal Q.; Wehlitz, Ralf

    2016-01-28

    We have experimentally investigated the double-photoionization process in C{sub 6}BrF{sub 5} using monochromatized synchrotron radiation. We compare our results with previously published data for partially deuterated benzene (C{sub 6}H{sub 3}D{sub 3}) over a wide range of photon energies from threshold to 270 eV. A broad resonance in the ratio of doubly to singly charged parent ions at about 65 eV appears shifted in energy compared to benzene data. This shift is due to the difference in the bond lengths in two molecules. A simple model can explain the shape of this resonance. At higher photon energies, we observe another broad resonance that can be explained as a second harmonic of the first resonance.

  4. Reductive Insertion of Elemental Chalcogens into Boron-Boron Multiple Bonds.

    PubMed

    Braunschweig, Holger; Dellermann, Theresa; Ewing, William C; Kramer, Thomas; Schneider, Christoph; Ullrich, Stefan

    2015-08-24

    The syntheses of sulfur- and selenium-bridged cyclic compounds containing boron stabilized by N-heterocyclic carbenes (NHCs) have been achieved by the reductive insertion of elemental chalcogens into boron-boron multiple bonds. The three pairs of bonding electrons between the boron atoms in the triply bonded diboryne enabled six-electron reduction reactions, resulting in the formation of [2.2.1]-bicyclic systems wherein bridgehead boron atoms are spanned by three chalcogen bridges. A similar reaction using a diborene (boron-boron double bond) resulted in the reductive transfer of both pairs of bonding electrons to three sulfur atoms, yielding a NHC-stabilized trisulfidodiborolane. The demonstration of these six- and four-electron reductions lends support to the presence of three and two pairs of bonding electrons between the boron atoms of the diboryne and diborene, respectively, a fact that may be useful in future discussions on bond order.

  5. Bond-slip behavior of CFRP plate-concrete interface

    NASA Astrophysics Data System (ADS)

    Cho, D. Y.; Park, S. K.; Hong, S. N.

    2011-11-01

    The paper deals with evaluation of the bond performance between a CFRP plate and concrete with respect to various compressive strengths of concrete and bond lengths of the CFRP plate as parameters. To consider stress conditions in the tensile zone of reinforced concrete (RC) structures, double-lap axial tension tests were conducted for eight specimens with CFRP plates bonded to concrete prisms. In addition, a simple linear bond-slip model for the CFRP plate/concrete joints, developed from the bond tests, was used. To verify the model proposed, a total of seven RC beams were strengthened with CFRP plates and tested in flexure employing various bond lengths, strengthening methods, and numbers of CFRP plates. A nonlinear finite-element analysis, with the bond-slip model incorporated in the DIANA program, was performed for the strengthened RC beams. Also, the results of flexural test and analytical predictions are found to be in close agreement in terms of yield and ultimate loads and ductility.

  6. The Nature of the Idealized Triple Bonds Between Principal Elements and the σ Origins of Trans-Bent Geometries-A Valence Bond Study.

    PubMed

    Ploshnik, Elina; Danovich, David; Hiberty, Philippe C; Shaik, Sason

    2011-04-12

    We describe herein a valence bond (VB) study of 27 triply bonded molecules of the general type X≡Y, where X and Y are main element atoms/fragments from groups 13-15 in the periodic table. The following conclusions were derived from the computational data: (a) Single π-bond and double π-bond energies for the entire set correlate with the "molecular electronegativity", which is the sum of the X and Y electronegativites for X≡Y. The correlation with the molecular electronegativity establishes a simple rule of periodicity: π-bonding strength generally increases from left to right in a period and decreases down a column in the periodic table. (b) The σ frame invariably prefers trans bending, while π-bonding gets destabilized and opposes the trans distortion. In HC≡CH, the π-bonding destabilization overrides the propensity of the σ frame to distort, while in the higher row molecules, the σ frame wins out and establishes trans-bent molecules with 2(1)/2 bonds, in accord with recent experimental evidence based on solid state (29)Si NMR of the Sekiguchi compound. Thus, in the trans-bent molecules "less bonds pay more". (c) All of the π bonds show significant bonding contributions from the resonance energy due to covalent-ionic mixing. This quantity is shown to correlate linearly with the corresponding "molecular electronegativity" and to reflect the mechanism required to satisfy the equilibrium condition for the bond. The π bonds for molecules possessing high molecular electronegativity are charge-shift bonds, wherein bonding is dominated by the resonance energy of the covalent and ionic forms, rather than by either form by itself.

  7. Low temperature reactive bonding

    DOEpatents

    Makowiecki, Daniel M.; Bionta, Richard M.

    1995-01-01

    The joining technique requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process.

  8. 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.)

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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 SiO2-to-SiO2 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.

  10. 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.

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

    PubMed

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

    2012-09-07

    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.

  12. 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)

  13. Rapid Adhesive Bonding of Composites

    NASA Technical Reports Server (NTRS)

    Stein, B. A.; Tyeryar, J. R.; Fox, R. L.; Sterling, S. Elmo, Jr.; Buckley, J. D.; Inge, Spencer V., Jr.; Burcher, L. G.; Wright, Robert E., Jr.

    1986-01-01

    Strong bonds created in less time and with less power than use of conventional bonding methods. Rapid adhesive bonding (RAB) technique for composites uses high-frequency induction heating toroids to quickly heat metallic susceptor impregnated with thermoplastic adhesive or sandwiched between thermoset or thermoplastic adhesive cloths or films. Susceptor steel screen or perforated steel foil.

  14. Synthesis of a uranium(VI)-carbene: reductive formation of uranyl(V)-methanides, oxidative preparation of a [R2C═U═O]2+ analogue of the [O═U═O]2+ uranyl ion (R = Ph2PNSiMe3), and comparison of the nature of U(IV)═C, U(V)═C, and U(VI)═C double bonds.

    PubMed

    Mills, David P; Cooper, Oliver J; Tuna, Floriana; McInnes, Eric J L; Davies, E Stephen; McMaster, Jonathan; Moro, Fabrizio; Lewis, William; Blake, Alexander J; Liddle, Stephen T

    2012-06-20

    We report attempts to prepare uranyl(VI)- and uranium(VI) carbenes utilizing deprotonation and oxidation strategies. Treatment of the uranyl(VI)-methanide complex [(BIPMH)UO(2)Cl(THF)] [1, BIPMH = HC(PPh(2)NSiMe(3))(2)] with benzyl-sodium did not afford a uranyl(VI)-carbene via deprotonation. Instead, one-electron reduction and isolation of di- and trinuclear [UO(2)(BIPMH)(μ-Cl)UO(μ-O){BIPMH}] (2) and [UO(μ-O)(BIPMH)(μ(3)-Cl){UO(μ-O)(BIPMH)}(2)] (3), respectively, with concomitant elimination of dibenzyl, was observed. Complexes 2 and 3 represent the first examples of organometallic uranyl(V), and 3 is notable for exhibiting rare cation-cation interactions between uranyl(VI) and uranyl(V) groups. In contrast, two-electron oxidation of the uranium(IV)-carbene [(BIPM)UCl(3)Li(THF)(2)] (4) by 4-morpholine N-oxide afforded the first uranium(VI)-carbene [(BIPM)UOCl(2)] (6). Complex 6 exhibits a trans-CUO linkage that represents a [R(2)C═U═O](2+) analogue of the uranyl ion. Notably, treatment of 4 with other oxidants such as Me(3)NO, C(5)H(5)NO, and TEMPO afforded 1 as the only isolable product. Computational studies of 4, the uranium(V)-carbene [(BIPM)UCl(2)I] (5), and 6 reveal polarized covalent U═C double bonds in each case whose nature is significantly affected by the oxidation state of uranium. Natural Bond Order analyses indicate that upon oxidation from uranium(IV) to (V) to (VI) the uranium contribution to the U═C σ-bond can increase from ca. 18 to 32% and within this component the orbital composition is dominated by 5f character. For the corresponding U═C π-components, the uranium contribution increases from ca. 18 to 26% but then decreases to ca. 24% and is again dominated by 5f contributions. The calculations suggest that as a function of increasing oxidation state of uranium the radial contraction of the valence 5f and 6d orbitals of uranium may outweigh the increased polarizing power of uranium in 6 compared to 5.

  15. Hydrogen bonding in ionic liquids.

    PubMed

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

    2015-03-07

    Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (ρBCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H σ* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak

  16. Evaluation of composite bonded joints

    SciTech Connect

    Whitworth, H.A.; Othieno, M.; Yin, S.W.

    1995-12-31

    The present investigation evaluates the influence of joining technique on the static and fatigue behavior of composite bonded joints. Specimens used in this investigation were LDF AS4/PEKK graphite/thermoplastic composites and IM6/3501-6 graphite/poxy composite laminates. Joints were made by either adhesive bonding or fusing bonding. For the adhesive bonded joints, in some cases specimens were bonded without any surface pretreatment while in other cases the surfaces were either grit blast or corona. treated prior to bonding. For the fusion bonded joints, joints were prepared by either induction welding or thermabonding. In addition, some specimens were conditioned in a wet environment for thirty days in order to observe the influence of moisture on the static strengths. During fatigue testing, the residual stiffness was continually monitored in order to assess the extent of fatigue damage development.

  17. 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.

  18. Bond strength of direct and indirect bonded brackets after thermocycling.

    PubMed

    Daub, Jacob; Berzins, David W; Linn, Brandon James; Bradley, Thomas Gerard

    2006-03-01

    Thermocycling simulates the temperature dynamics in the oral environment. With direct bonding, thermocycling reduces the bond strength of orthodontic adhesives to tooth structure. The purpose of this study was to evaluate the shear bond strengths (SBS) of one direct and two indirect bonding methods/adhesives after thermocycling. Sixty human premolars were divided into three groups. Teeth in group 1 were bonded directly with Transbond XT. Teeth in group 2 were indirect bonded with Transbond XT/Sondhi Rapid Set, which is chemically cured. Teeth in group 3 were indirect bonded with Enlight LV/Orthosolo and light cured. Each sample was thermocycled between 5 degrees C and 55 degrees C for 500 cycles. Mean SBS in groups 1, 2, and 3 were not statistically significantly different (13.6 +/- 2.9, 12.3 +/- 3.0, and 11.6 +/- 3.2 MPa, respectively; P > .05). However, when these values were compared with the results of a previous study using the same protocol, but without thermocycling, the SBS was reduced significantly (P = .001). Weibull analysis further showed that group 3 had the lowest bonding survival rate at the minimum clinically acceptable bond-strength range. The Adhesive Remnant Index was also determined, and group 2 had a significantly (P < .05) higher percentage of bond failures at the resin/enamel interface.

  19. Mothers and Daughters in the Fiction of Joyce Carol Oates: The Terror and Beauty of Doubling.

    ERIC Educational Resources Information Center

    Mattes, Eleanor

    Joyce Carol Oates is unique in American fiction for her portrayals of the terror and the beauty in the mother-daughter relationship--the tensions and the bonds created by this particular form of doubling. Her more interesting explorations portraying some deeply pathological and some positive aspects of this form of doubling include the following:…

  20. 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.

  1. How many hydrogen-bonded α-turns are possible?

    PubMed

    Schreiber, Anette; Schramm, Peter; Hofmann, Hans-Jörg

    2011-06-01

    The formation of α-turns is a possibility to reverse the direction of peptide sequences via five amino acids. In this paper, a systematic conformational analysis was performed to find the possible isolated α-turns with a hydrogen bond between the first and fifth amino acid employing the methods of ab initio MO theory in vacuum (HF/6-31G*, B3LYP/6-311 + G*) and in solution (CPCM/HF/6-31G*). Only few α-turn structures with glycine and alanine backbones fulfill the geometry criteria for the i←(i + 4) hydrogen bond satisfactorily. The most stable representatives agree with structures found in the Protein Data Bank. There is a general tendency to form additional hydrogen bonds for smaller pseudocycles corresponding to β- and γ-turns with better hydrogen bond geometries. Sometimes, this competition weakens or even destroys the i←(i + 4) hydrogen bond leading to very stable double β-turn structures. This is also the reason why an "ideal" α-turn with three central amino acids having the perfect backbone angle values of an α-helix could not be localized. There are numerous hints for stable α-turns with a distance between the C(α)-atoms of the first and fifth amino acid smaller than 6-7 Å, but without an i←(i + 4) hydrogen bond.

  2. Efficient simulation of semiflexible polymers with stiff bonds

    NASA Astrophysics Data System (ADS)

    Barkema, Gerard T.; van Leeuwen, J. M. J.

    2017-01-01

    We investigate the simulation of stiff (extensible) and rigid (inextensible) semiflexible polymers in solution. In particular, we focus on polymers represented as chains of beads, interconnected by bonds with a low to zero extensibility, and significant persistence in the bond orientations along the chain, whose dynamical behavior is described by the Langevin equation. We review the derivation of the pseudopotential needed for rigid bonds. The efficiency of a number of routines for such simulations is determined. We propose a routine for handling rigid bonds which is, for longer chains, substantially more efficient than the existing ones. We also show that for extensible polymers, the Rouse modes can be exploited to achieve highly efficient simulations. At realistic values for the extensibility, e.g., that of double-stranded DNA, the simulations are orders of magnitude faster than those for rigid bonds. With increasing stiffness, however, the allowable time step and hence the efficiency decreases, until a crossover point is reached below which the routines with rigid bonds are more efficient; we present a numerical estimate of this crossover point.

  3. 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.

  4. [SIBSytem: innovation for bracket bonding?].

    PubMed

    Moreau, Alexis

    2013-06-01

    The orthodontic bracket placement has known two major improvements these last fifty years: first with the ability of bonding brackets directly on the enamel (Newmann 1965); second with the indirect bonding procedure introduced by Silvermann and Cohen in 1972. If we put aside the technological evolutions of bonding materials (brackets and adhesives), few refinements have occurred regarding the protocols in this period of time. Furthermore, direct bonding procedure seems to be used by a majority of orthodontists despite the rapidity, accuracy and ergonomics promised by indirect bonding protocol. The main originality of the system detailed in this article is to bond orthodontic brackets in a virtually predetermined position with indirect bonding advantages but with the efficiency of direct bonding because the adhesive is applied directly on the bracket base without pre-bonding necessity. This innovation has been allowed by the use of up-to-date CFAO technology. The article first describes the two components of the SIBSystem (SIBClip and SIBTray) and details the manufacturing stages. The clinical use is then evoked as well as the cautions and limits of this innovative bonding system.

  5. 27 CFR 28.66 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... bonds. In all cases where the penal sum of any bond 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 to... of any bond to less than its full penal sum. Strengthening bonds shall show the current date...

  6. 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.

  7. 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.

  8. 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

  9. Multidimensional period doubling structures.

    PubMed

    Lee, Jeong Yup; Flom, Dvir; Ben-Abraham, Shelomo I

    2016-05-01

    This paper develops the formalism necessary to generalize the period doubling sequence to arbitrary dimension by straightforward extension of the substitution and recursion rules. It is shown that the period doubling structures of arbitrary dimension are pure point diffractive. The symmetries of the structures are pointed out.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Wafer bonded epitaxial templates for silicon heterostructures

    DOEpatents

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

    2008-03-11

    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.

  15. Push-out bond strengths of two fiber post types bonded with different dentin bonding agents.

    PubMed

    Topcu, Fulya Toksoy; Erdemir, Ugur; Sahinkesen, Gunes; Mumcu, Emre; Yildiz, Esra; Uslan, Ibrahim

    2010-05-01

    The aim of this study was to evaluate the regional push-out bond strengths for two fiber-reinforced post types using three different dentin bonding agents. Sixty single-rooted extracted human first premolar teeth were sectioned below the cemento-enamel junction, and the roots were endodontically treated. Following standardized post space preparations, the roots were divided into two fiber-post groups (Glassix and Carbopost), and further divided into three subgroups of 10 specimens each for the bonding systems self-etching dentin bonding agents (Clearfil SE Bond and Optibond all-in-one), and total-etching dentin bonding agent (XP Bond). A dual-cure resin luting cement (Maxcem) was then placed in the post spaces and posts were then seated into the root canals polymerized through the cervical portion. The roots were then cut into 3-mm thick sections. Push-out tests were performed at a crosshead speed of 0.5 mm/min. The data were analyzed with multivariate ANOVA (alpha = 0.05). The morphology of interface between different dentin bonding agents from the cervical sections were analyzed with SEM. Glass fiber-reinforced posts demonstrated significantly higher push-out bond strengths than carbon fiber-reinforced posts (p < 0.001). Bond strength values decreased significantly from the cervical to the apical root canal regions (p < 0.001). Self-etching dentin adhesive Clearfil SE Bond and total-etching dentin adhesive XP Bond demonstrated similar bond strengths values and this was significantly higher compared with the Optibond all-in-one in cervical root canal region. In conclusion, in all root segments, the glass fiber-reinforced posts provided significantly increased post retention than the carbon fiber-reinforced posts, regardless of the adhesive used.

  16. Hydrogen bonding in the hexagonal ice surface.

    PubMed

    Barnett, Irene Li; Groenzin, Henning; Shultz, Mary Jane

    2011-06-16

    A recently developed technique in sum frequency generation spectroscopy, polarization angle null (or PAN-SFG), is applied to two orientations of the prism face of hexagonal ice. It is found that the vibrational modes of the surface are similar in different faces. As in the basal face, the prism face of ice contains five dominant resonances: 3096, 3146, 3205, 3253, and 3386 cm(-1). On the basal face, the reddest resonance occurs at 3098 cm(-1); within the bandwidth, the same as the prism face. On both the prism and basal faces, this mode contains a significant quadrupole component and is assigned to the bilayer stitching hydrogen bonds. The bluest of the resonances, 3386 cm(-1), occurs slightly blue-shifted at 3393 cm(-1) in the basal face. The prism face has two orientations: one with the optic or c axis in the input plane (the plane formed by the surface normal and the interrogating beam propagation) and one with the c axis perpendicular to the input plane. The 3386 cm(-1) mode has significant intensity only with the c axis in the input plane. On the basis of these orientation characteristics, the 3386 cm(-1) mode is assigned to double-donor molecules in either the top half bilayer or in the lower half bilayer. On the basis of frequency considerations, it is assigned to double-donor molecules in the top half bilayer. These are water molecules containing a nonbonded lone pair. In addition to identification of the components of the broad hydrogen-bonded region, PAN-SFG measures the tangential vs longitudinal content of the vibrational modes. In accord with previous suggestions, the lower frequency modes are predominantly tangential, whereas the higher frequency modes are mainly longitudinal. On the prism face, the 3386 cm(-1) mode is entirely longitudinal.

  17. Emerging double helical nanostructures.

    PubMed

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

    2014-08-21

    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.

  18. 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

  19. 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.

  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. 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.

  2. 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.

  3. 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.

  4. Ultrasonic phosphate bonding of nanoparticles.

    PubMed

    Bassett, David C; Merle, Geraldine; Lennox, Bruce; Rabiei, Reza; Barthelat, François; Grover, Liam M; Barralet, Jake E

    2013-11-06

    Low intensity ultrasound-induced radicals interact with surface adsorbed orthophosphate to bond nanoparticles with high mechanical strength and surface area. Dissimilar materials could be bonded to form robust metallic, ceramic, and organic composite microparticles. 3D nanostructures of a hydrated and amorphous electrocatalyst with carbon nanotubes were also constructed which exceeded the resistance-limited efficiency of 2D electrodes.

  5. Tunable infrared generation with diffusion-bonded-stacked gallium arsenide

    NASA Astrophysics Data System (ADS)

    Zheng, Dong

    quantum gain, was measured at 16.6 μm. Other DBS GaAs devices for frequency doubling of CO2 laser radiation and difference frequency mixing of various laser sources were demonstrated. Tunable MIR radiation from 4.7 μm to 17.6 μm was generated demonstrating feasibility of diffusion bonded structures to generate broadly tunable MIR wavelengths.

  6. Benchmarking Density Functionals for Chemical Bonds of Gold.

    PubMed

    Kepp, Kasper P

    2017-03-09

    Gold plays a major role in nanochemistry, catalysis, and electrochemistry. Accordingly, hundreds of studies apply density functionals to study chemical bonding with gold, yet there is no systematic attempt to assess the accuracy of these methods applied to gold. This paper reports a benchmark against 51 experimental bond enthalpies of AuX systems and seven additional polyatomic and cationic molecules. Twelve density functionals were tested, covering meta functionals, hybrids with variable HF exchange, double-hybrid, dispersion-corrected, and nonhybrid GGA functionals. The defined benchmark data set probes all types of bonding to gold from very electronegative halides that force Au(+) electronic structure, via covalently bonded systems, hard and soft Lewis acids and bases that either work against or complement the softness of gold, the Au2 molecule probing gold's bond with itself, and weak bonds between gold and noble gases. Zero-point vibrational corrections are relatively small for Au-X bonds, ∼ 11-12 kJ/mol except for Au-H bonds. Dispersion typically provides ∼5 kJ/mol of the total bond enthalpy but grows with system size and is 10 kJ/mol for AuXe and AuKr. HF exchange and LYP correlation produce weaker bonds to gold. Most functionals provide similar trend accuracy, though somewhat lower for M06 and M06L, but very different numerical accuracy. Notably, PBE and TPSS functionals with dispersion display the smallest numerical errors and very small mean signed errors (0-6 kJ/mol), i.e. no bias toward over- or under-binding. Errors are evenly distributed versus atomic number, suggesting that relativistic effects are treated fairly; the mean absolute error is almost halved from B3LYP (45 kJ/mol) to TPSS and PBE (23 kJ/mol, including difficult cases); 23 kJ/mol is quite respectable considering the diverse bonds to gold and the complication of relativistic effects. Thus, studies that use DFT with effective core potentials for gold chemistry, with no alternative due

  7. 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

  8. Halogen bonding (X-bonding): A biological perspective

    PubMed Central

    Scholfield, Matthew R; Zanden, Crystal M Vander; Carter, Megan; Ho, P Shing

    2013-01-01

    The concept of the halogen bond (or X-bond) has become recognized as contributing significantly to the specificity in recognition of a large class of halogenated compounds. The interaction is most easily understood as primarily an electrostatically driven molecular interaction, where an electropositive crown, or σ-hole, serves as a Lewis acid to attract a variety of electron-rich Lewis bases, in analogous fashion to a classic hydrogen bonding (H-bond) interaction. We present here a broad overview of X-bonds from the perspective of a biologist who may not be familiar with this recently rediscovered class of interactions and, consequently, may be interested in how they can be applied as a highly directional and specific component of the molecular toolbox. This overview includes a discussion for where X-bonds are found in biomolecular structures, and how their structure–energy relationships are studied experimentally and modeled computationally. In total, our understanding of these basic concepts will allow X-bonds to be incorporated into strategies for the rational design of new halogenated inhibitors against biomolecular targets or toward molecular engineering of new biological-based materials. PMID:23225628

  9. 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.

  10. 27 CFR 25.95 - New bond.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false New bond. 25.95 Section 25... TREASURY LIQUORS BEER Bonds and Consents of Surety § 25.95 New bond. The appropriate TTB officer may at any time, at his or her discretion, require a new bond. A new bond is required immediately in the case...

  11. 27 CFR 25.95 - New bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false New bond. 25.95 Section 25... TREASURY LIQUORS BEER Bonds and Consents of Surety § 25.95 New bond. The appropriate TTB officer may at any time, at his or her discretion, require a new bond. A new bond is required immediately in the case...

  12. 21 CFR 1005.23 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... IMPORTATION OF ELECTRONIC PRODUCTS Bonding and Compliance Procedures § 1005.23 Bonds. The bond required under section 360(b) of the Act shall be executed by the owner or consignee on the appropriate form of a customs single-entry bond, customs Form 7551 or term bond, customs Form 7553 or 7595, containing a condition...

  13. 27 CFR 24.153 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 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... limiting the amount of either bond to less than its full penal sum. Strengthening bonds will show...

  14. 27 CFR 19.246 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Strengthening bonds. In all cases when the penal sum of any bond becomes insufficient, the principal shall either give a strengthening bond with the same surety to attain a sufficient penal sum, or give a new... amount of any bond to less than its full penal sum. Strengthening bonds shall show the current date...

  15. Molecular theory for the phase equilibria and cluster distribution of associating fluids with small bond angles.

    PubMed

    Marshall, Bennett D; Chapman, Walter G

    2013-08-07

    We develop a new theory for associating fluids with multiple association sites. The theory accounts for small bond angle effects such as steric hindrance, ring formation, and double bonding. The theory is validated against Monte Carlo simulations for the case of a fluid of patchy colloid particles with three patches and is found to be very accurate. Once validated, the theory is applied to study the phase diagram of a fluid composed of three patch colloids. It is found that bond angle has a significant effect on the phase diagram and the very existence of a liquid-vapor transition.

  16. Hydroperoxides as Hydrogen Bond Donors

    NASA Astrophysics Data System (ADS)

    Møller, Kristian H.; Tram, Camilla M.; Hansen, Anne S.; Kjaergaard, Henrik G.

    2016-06-01

    Hydroperoxides are formed in the atmosphere following autooxidation of a wide variety of volatile organics emitted from both natural and anthropogenic sources. This raises the question of whether they can form hydrogen bonds that facilitate aerosol formation and growth. Using a combination of Fourier transform infrared spectroscopy, FT-IR, and ab initio calculations, we have compared the gas phase hydrogen bonding ability of tert-butylhydroperoxide (tBuOOH) to that of tert-butanol (tBuOH) for a series of bimolecular complexes with different acceptors. The hydrogen bond acceptor atoms studied are nitrogen, oxygen, phosphorus and sulphur. Both in terms of calculated redshifts and binding energies (BE), our results suggest that hydroperoxides are better hydrogen bond donors than the corresponding alcohols. In terms of hydrogen bond acceptor ability, we find that nitrogen is a significantly better acceptor than the other three atoms, which are of similar strength. We observe a similar trend in hydrogen bond acceptor ability with other hydrogen bond donors including methanol and dimethylamine.

  17. Method of bonding

    DOEpatents

    Saller, deceased, Henry A.; Hodge, Edwin S.; Paprocki, Stanley J.; Dayton, Russell W.

    1987-12-01

    1. A method of making a fuel-containing structure for nuclear reactors, comprising providing an assembly comprising a plurality of fuel units; each fuel unit consisting of a core plate containing thermal-neutron-fissionable material, sheets of cladding metal on its bottom and top surfaces, said cladding sheets being of greater width and length than said core plates whereby recesses are formed at the ends and sides of said core plate, and end pieces and first side pieces of cladding metal of the same thickness as the core plate positioned in said recesses, the assembly further comprising a plurality of second side pieces of cladding metal engaging the cladding sheets so as to space the fuel units from one another, and a plurality of filler plates of an acid-dissolvable nonresilient material whose melting point is above 2000.degree. F., each filler plate being arranged between a pair of said second side pieces and the cladding plates of two adjacent fuel units, the filler plates having the same thickness as the second side pieces; the method further comprising enclosing the entire assembly in an envelope; evacuating the interior of the entire assembly through said envelope; applying inert gas under a pressure of about 10,000 psi to the outside of said envelope while at the same time heating the assembly to a temperature above the flow point of the cladding metal but below the melting point of any material of the assembly, whereby the envelope is pressed against the assembly and integral bonds are formed between plates, sheets, first side pieces, and end pieces and between the sheets and the second side pieces; slowly cooling the assembly to room temperature; removing the envelope; and dissolving the filler plates without attacking the cladding metal.

  18. 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.

  19. Hydrogen bonded arrays: the power of multiple hydrogen bonds.

    PubMed

    Shokri, Alireza; Schmidt, Jacob; Wang, Xue-Bin; Kass, Steven R

    2012-02-01

    Hydrogen bond interactions in small covalent model compounds (i.e., deprotonated polyhydroxy alcohols) were measured by negative ion photoelectron spectroscopy. The experimentally determined vertical and adiabatic electron detachment energies for (HOCH(2)CH(2))(2)CHO(-)(2a), (HOCH(2)CH(2))(3)CO(-) (3a), and (HOCH(2)CH(2)CH(OH)CH(2))(3)CO(-) (4a)reveal that hydrogen-bonded networks can provide enormous stabilizations and that a single charge center not only can be stabilized by up to three hydrogen bonds but also can increase the interaction energy between noncharged OH groups by 5.8 kcal mol(-1) or more per hydrogen bond. This can lead to pK(a) values that are very different from those in water and can provide some of the impetus for catalytic processes.

  20. Hydrogen Bonded Arrays: The Power of Multiple Hydrogen Bonds

    SciTech Connect

    Shokri, Alireza; Schmidt, Jacob C.; Wang, Xue B.; Kass, Steven R.

    2012-02-01

    Hydrogen bond interactions in small covalent model compounds (i.e. deprotonated polyhydroxy alcohols) were measured by negative ion photoelectron spectroscopy. The experimentally determined vertical and adiabatic electron detachment energies for (HOCH2CH2)2CHO (2a), (HOCH2CH2) 3CO (3a) and (HOCH2CH2CH(OH)CH2)3CO (4a) reveal that hydrogen-bonded networks can provide enormous stabilizations, and that a single charge center not only can be stabilized by up to 3 hydrogen bonds but it can increase the interaction energy between non-charged OH groups by 5.8 kcal mol1 or more per hydrogen bond. This can lead to pKa values that are very different than in water, and provide some of the impetus for catalytic processes.

  1. Method of bond strength evaluation for silicon direct wafer bonding

    NASA Astrophysics Data System (ADS)

    Spivak, Alexander; Avagyan, Avag; Davies, Brady R.

    2001-09-01

    A crack-opening method used for characterization of silicon direct wafer bonding (DWB) techniques was analyzed. Mathematical model describing the influence of the pattern shape on the wafer pair resistance curve, so-called the R-curve, was developed. Two-dimensional patterns were created on a mirror-polished silicon wafer surface by a combination of photolithography, deposition and etching steps. Experimental observations did show that structured wafers can be used for large bond energy measurements. We propose utilization of structured wafers for bond energy measurements. It allows R-curve shape manipulation, increases the method sensitivity, and reduces probability of wafer failure. The resulting theory can also be used for developing new experimental methods for large bond energy measurements.

  2. 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.

  3. 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.

  4. Molecular orbital study of the bond-valence sum rule using Lewis-electron pair theory.

    PubMed

    Mohri, Fumihito

    2003-04-01

    The bond-valence sum rule has been examined by molecular-orbital methods related to spin-coupling matrix theory [Okada & Fueno (1976). Bull. Chem. Soc. Jpn, 49, 1524-1530], to give a new formulation of the Lewis-electron pair concept. It is shown that the 'pair-coupling population' between atoms M and X exhibits the same behaviour as the bond valence between them. A quantum chemical definition for bond valence is proposed and successfully applied to Al(2)Cl(6), Te(4)Cl(16) and Al(2)Be(3)(SiO(3))(6) (beryl). Using an alternative bond-valence definition it is shown that for oxides the bond valence can possibly be taken as the double pair-coupling population.

  5. 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.

  6. 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

  7. Mechanics and fracture of hybrid material interface bond

    NASA Astrophysics Data System (ADS)

    Wang, Jialai

    Considering current and future applications of hybrid materials and structures in civil engineering, the strength and durability of interface bond between the conventional materials and composites are critical to development of such products. Conventional methods mostly used for analysis of isotropic materials may not be well suitable or accurate enough for a system made of anisotropic materials with relatively low shear stiffness. A need exists for developing more accurate and explicit analytical solutions for hybrid material interface analysis and related novel experimental characterization techniques. In this study, a combined analytical and experimental approach to characterize hybrid material interface bond is developed. Using a shear deformable plate theory and an elastic interface model, a mechanics approach for interface analysis of hybrid material bond under general loading is first proposed. The resulting closed-form solution of interface stress distribution is used to compute strain energy release rate (SERB) and stress intensity factor (SIF) of the interface with or without adhesive bond. This approach is then extended to delamination of composite structures under generic loading conditions. Second, novel experimental approaches for characterization of hybrid material bonded interfaces are presented. To account for the crack tip deformations, a tapered beam on elastic foundation (TBEF) is developed. Based on the TBEF model, analysis and design of two novel fracture specimens, Tapered Double Cantilever Beam (TDCB) and Tapered End Notched Flexure (TENF), are proposed, and they are effectively used in fracture toughness tests of bonded interface under Mode-I and Mode-II loadings, respectively. A constant compliance rate change over certain crack length range is achieved for the TDCB and TENF specimens, and it alleviates the necessity of experimental compliance calibration tests. The fracture toughness data obtained from the experiments are useful to

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

    PubMed

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

    2016-05-07

    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

  9. 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.

  10. Interaction of DAPI with double-stranded ribonucleic acids.

    PubMed Central

    Manzini, G; Xodo, L; Barcellona, M L; Quadrifoglio, F

    1985-01-01

    The interaction of DAPI with natural and synthetic double-stranded polyribonucleotides was studied with different optical and calorimetric methods. The results were similar to those obtained previously with double-stranded polydeoxynucleotides, i.e. two interaction modes, the first of which shows high affinity for AU clusters and consequent strong fluorescence enhancement. The results suggest caution in the use of DAPI as selective fluorescent staining agent for DNA in the presence of RNA. A narrow groove binding model with hydrogen bonds between DAPI and AU pairs is proposed. An intercalation mechanism can be excluded because of the non planarity of DAPI molecule. PMID:4080554

  11. Synthesis and [2 + 2] cycloaddition of bimethyleneketene acetals. Reaction with C[sub 60] and facile hydrolysis of the C-C bond connected to C[sub 60

    SciTech Connect

    Yamago, Shigeru; Takeichi, Atsuo; Nakamura, Eiichi )

    1994-02-09

    We report here that the O-alkylated enolates of cyclopropanecarboxylates (dimethyleneketene acetals 3) can be prepared from readily available precursors, and that they are extemely reactive, serving as useful surrogates of the elusive parent enolates. Their utility is illustrated by the [2 + 2] cycloaddition to electron-deficient olefins, which, after hydrolytic workup, gives rise to the Michael addition products: a type of reaction product previously unavailable. We also found that 3 reacts smoothly with C[sub 60] to give the [2 + 2] adduct 5 and, most remarkably, that the asterisked C[minus]C [sigma] bond in 5 directly connected to the fullerene core is hydrolytically unstable and can be quantitatively cleaved with aqueous acid. 15 refs., 1 tab.

  12. 27 CFR 19.245 - Bonds and penal sums of bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bonds and penal sums of... Bonds and penal sums of bonds. The bonds, and the penal sums thereof, required by this subpart, are as follows: Penal Sum Type of bond Basis Minimum Maximum (a) Operations bond: (1) One plant bond—...

  13. 77 FR 553 - Surety Companies Acceptable on Federal Bonds: Termination; Western Bonding Company

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-05

    ... Fiscal Service Surety Companies Acceptable on Federal Bonds: Termination; Western Bonding Company AGENCY... Company (NAIC 13191) under 31 U.S.C. 9305 to qualify as an acceptable surety on Federal bonds is... bonds, including continuous bonds, currently in force with above listed Company, bond-approving...

  14. Energetics and electronic structure of double-walled boron nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Hui; Ismail-Beigi, Sohrab

    2010-03-01

    Single-walled boron nanotubes have been studied extensively since their first successful fabrication in experiments. On the other hand, double-walled or multi-walled boron nanotubes have not yet been discussed in literature. Here, using density functional theory, we present a stable semiconducting two-dimensional double-layered boron sheet, which is 0.14 eV/atom more stable than the most stable single-layered α-sheet [1]. This double-layered sheet is stabilized due to the formation of inter-layer bonds. We show that double-walled boron nanotubes made from this double-layered sheet are all semiconducting. These double-walled nanotubes are more stable than single-walled ones for large nanotubes, but become less energetically favorable when the tube radius is smaller than 20 å due to their large curvature energies. To reduce the large curvature energies, we construct double-walled nanotubes whose inner and outer walls have different number of atoms around their circumference. The resulting nanotubes are more stable than single-walled ones for all radii.[4pt] [1] H. Tang, and S. Ismail-Beigi, PRL 99, 115501 (2007).

  15. 27 CFR 25.94 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Requirement. When the penal sum of the brewer's bond (calculated as provided in § 25.93) in effect is not... strengthening bond in sufficient penal sum if the surety is the same as on the bond in effect. If the surety is... bond may not in any way release a former bond or limit a bond to less than the full penal sum. (c)...

  16. Testing Adhesive Bonds to Cloths

    NASA Technical Reports Server (NTRS)

    Thomann, David G.

    1987-01-01

    Nondestructive tool simple and inexpensive. Easy-to-use tool nondestructively tests strength of adhesive bond between cloth and straight rigid edge. Developed for testing advanced flexible reusable surface insulation.

  17. 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.

  18. Semiquantal analysis of hydrogen bond

    NASA Astrophysics Data System (ADS)

    Ando, Koji

    2006-07-01

    The semiquantal time-dependent Hartree (SQTDH) theory is applied to the coupled Morse and modified Lippincott-Schroeder (LS) model potentials of hydrogen bond. The structural correlation between the heavy atoms distance and the proton position, the geometric isotope effect, the energy of hydrogen bond formation, and the proton vibrational frequency shift are examined in a broad range of structural parameters. In particular, the geometric isotope effect is found to depend notably on the choice of the potential model, for which the LS potential gives the isotope shift of the heavy atoms distance in the range of 0.02-0.04Å, in quantitative agreement with the experimental findings from assortment of hydrogen bonding crystals. The fourth-order expansion approximation to the semiquantal extended potential was confirmed to be highly accurate in reproducing the full SQTDH results. The approximation is computationally efficient and flexible enough to be applied to general models of hydrogen bond.

  19. 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.

  20. Bond percolation in higher dimensions

    NASA Astrophysics Data System (ADS)

    Corwin, Eric I.; Stinchcombe, Robin; Thorpe, M. F.

    2013-07-01

    We collect results for bond percolation on various lattices from two to fourteen dimensions that, in the limit of large dimension d or number of neighbors z, smoothly approach a randomly diluted Erdős-Rényi graph. We include results on bond-diluted hypersphere packs in up to nine dimensions, which show the mean coordination, excess kurtosis, and skewness evolving smoothly with dimension towards the Erdős-Rényi limit.

  1. Machine Gun Liner Bond Strength

    DTIC Science & Technology

    2007-08-01

    investigation does not constitute a complete analysis of liner failures in the M2 machine gun. The fact that two different liner-failure modes were...An order-of-magnitude estimate can be made of the bond strength in this case using a standard elastic analysis and some reasonable assumptions... analysis of the forces on the machine gun bullet, it was found that the measured bond strength was adequate to resist the reaction forces produced when

  2. Catalytic σ-Bond Metathesis

    NASA Astrophysics Data System (ADS)

    Reznichenko, Alexander L.; Hultzsch, Kai C.

    This account summarizes information on recently reported applications of organo-rare-earth metal complexes in various catalytic transformations of small molecules. The σ-bond metathesis at d0rare-earth metal centers plays a pivotal role in carbon-carbon and carbon-heteroatom bond forming processes. Relevant mechanistic details are discussed and the focus of the review lies in practical applications of organo-rare-earth metal complexes.

  3. Biomimetic oxidation with molecular oxygen. Selective carbon-carbon bond cleavage of 1,2-diols by molecular oxygen and dihydropyridine in the presence of iron-porphyrin catalysts

    SciTech Connect

    Okamoto, T.; Sasaki, K.; Oka, S.

    1988-02-17

    The selective carbon-carbon bond cleavage of 1,2-diols in the presence of an iron-porphyrin complex, molecular oxygen, and 1-benzyl-3-carbamoyl-1,4-dihydropyridine is reported. The C-C bonds of aryl-substituted ethane-1,2-diols were cleaved exclusively to aldehydes or ketones as the oxidation products at room temperature. The reaction rates were influenced by the steric hindrance of the substituents both in the catalysts and diols, but no differences in the reactivities were observed between the two stereo isomers (meso and dl) of diols. A kinetic analysis of this bond cleavage reaction is consistent with the reaction mechanism consisting of the initial binding of diol on the active catalyst forming an intermediate complex and its subsequent breakdown in the rate-determining step of the catalytic cycle. The initial binding step is favorable for electron-deficient diols and is influenced by steric hindrance, whereas the rate-determining bond cleavage step is accelerated by electron-rich diols and unaffected by the steric effect. The mechanism of this diol cleavage reaction is discussed on the basis of these observations.

  4. Barrelane-like germanium clusters in Eu 3Ge 5: Crystal structure, chemical bonding and physical properties

    NASA Astrophysics Data System (ADS)

    Budnyk, Sergij; Weitzer, Franz; Kubata, Christof; Prots, Yurii; Akselrud, Lev G.; Schnelle, Walter; Hiebl, Kurt; Nesper, Reinhard; Wagner, Frank R.; Grin, Yuri

    2006-08-01

    Formation and crystal structure of the binary germanide Eu 3Ge 5 were investigated in detail. The compound forms peritectically at 1008 °C and does not undergo any phase transition down to room temperature. The crystal structure was determined first from X-ray powder diffraction data and was later confirmed by single-crystal X-ray diffraction: structure type Pu 3Pd 5, space group Cmcm (no. 63), a=9.7675(4) Å, b=7.9681(3) Å, c=9.8562(3) Å. The main building blocks are Ge 56- cluster anions surrounded by Eu 2+ cations. The nearly tetragonal-pyramidal shape is suggested by the interatomic distances. Contrary to that, the bonding analysis with the electron localization function (ELF) reveals only two- and three-bonded germanium atoms forming a strongly distorted [1.1.1]-barrelane-like cluster. Despite the formal electron deficiency, compared to the barrelane C 5H 8, the electron counting in the cluster anion and its conformation cannot be interpreted applying the Wade's rules. In accordance with the calculated electronic density of states, Eu 3Ge 5 shows a metal-like temperature dependence of the electrical resistivity with a sharp change of ρ(T) slope at the Néel point. Above the Néel point the inverse magnetic susceptibility reveals Curie-Weiss behavior with an effective moment of 8.11 μB (Eu 2+, 4 f7 configuration) in agreement with the analysis of the chemical bonding. The 4 f7 electronic configuration of europium is confirmed by Eu- LIII X-ray absorption spectroscopy.

  5. Double-shell inertial confinement fusion target fabrication

    SciTech Connect

    Hatcher, C.W.; Lorensen, L.E.; Weinstein, B.W.

    1981-04-01

    Double-shell targets may be required for the next generation of inertial confinement fusion targets since the energy available for driving the implosion is limited with current drivers. The use of double-shell targets to provide a velocity multiplication driven implosion is an alternative to increased driver energy. First generation hemishells, from which spherical shells are constructed, were fabricated by micromachining coated mandrels and by molding. The remachining of coated mandrels will be described in detail in this article. Techniques were developed for coating the microsized mandrels with polymeric and metallic materials by methods including conformal coating, vapor deposition, plasma polymerization and thermoforming. Micropositioning equipment and bonding techniques have also been developed to assemble the hemishells about a fuel pellet maintaining a spherical concentricity of better than 2 mm and voids in the hemishell bonding line of a few hundred angstroms or less.

  6. Double checking: a second look

    PubMed Central

    Chreim, Samia; Forster, Alan

    2015-01-01

    Abstract Rationale, aims and objectives Double checking is a standard practice in many areas of health care, notwithstanding the lack of evidence supporting its efficacy. We ask in this study: ‘How do front line practitioners conceptualize double checking? What are the weaknesses of double checking? What alternate views of double checking could render it a more robust process?’ Method This is part of a larger qualitative study based on 85 semi‐structured interviews of health care practitioners in general internal medicine and obstetrics and neonatology; thematic analysis of the transcribed interviews was undertaken. Inductive and deductive themes are reported. Results Weaknesses in the double checking process include inconsistent conceptualization of double checking, double (or more) checking as a costly and time‐consuming procedure, double checking trusted as an accepted and stand‐alone process, and double checking as preventing reporting of near misses. Alternate views of double checking that would render it a more robust process include recognizing that double checking requires training and a dedicated environment, Introducing automated double checking, and expanding double checking beyond error detection. These results are linked with the concepts of collective efficiency thoroughness trade off (ETTO), an in‐family approach, and resilience. Conclusion(s) Double checking deserves more questioning, as there are limitations to the process. Practitioners could view double checking through alternate lenses, and thus help strengthen this ubiquitous practice that is rarely challenged. PMID:26568537

  7. 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.

  8. 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.

  9. Double Photoionization Near Threshold

    NASA Technical Reports Server (NTRS)

    Wehlitz, Ralf

    2007-01-01

    The threshold region of the double-photoionization cross section is of particular interest because both ejected electrons move slowly in the Coulomb field of the residual ion. Near threshold both electrons have time to interact with each other and with the residual ion. Also, different theoretical models compete to describe the double-photoionization cross section in the threshold region. We have investigated that cross section for lithium and beryllium and have analyzed our data with respect to the latest results in the Coulomb-dipole theory. We find that our data support the idea of a Coulomb-dipole interaction.

  10. 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.

  11. Relationship between chemical structure and supramolecular effective molarity for formation of intramolecular H-bonds.

    PubMed

    Sun, Hongmei; Hunter, Christopher A; Navarro, Cristina; Turega, Simon

    2013-09-04

    Effective molarity (EM) is a key parameter that determines the efficiency of a range of supramolecular phenomena from the folding of macromolecules to multivalent ligand binding. Coordination complexes formed between zinc porphyrins equipped H-bond donor sites and pyridine ligands equipped with H-bond acceptor sites have allowed systematic quantification of EM values for the formation of intramolecular H-bonds in 240 different systems. The results provide insights into the relationship of EM to supramolecular architecture, H-bond strength, and solvent. Previous studies on ligands equipped with phosphonate diester and ether H-bond acceptors were inconclusive, but the experiments described here on ligands equipped with phosphine oxide, amide, and ester H-bond acceptors resolve these ambiguities. Chemical double-mutant cycles were used to dissect the thermodynamic contributions of individual H-bond interactions to the overall stabilities of the complexes and hence determine the values of EM, which fall in the range 1-1000 mM. Solvent has little effect on EM, and the values measured in toluene and 1,1,2,2-tetrachloroethane are similar. For H-bond acceptors that have similar geometries but different H-bond strengths (amide and ester), the values of EM are very similar. For H-bond acceptors that have different geometries but similar H-bond strengths (amide and phosphonate diester), there is little correlation between the values of EM. These results imply that supramolecular EMs are independent of solvent and intrinsic H-bond strength but depend on supramolecular architecture and geometric complementarity.

  12. Topology of electron charge density for chemical bonds from valence bond theory: a probe of bonding types.

    PubMed

    Zhang, Lixian; Ying, Fuming; Wu, Wei; Hiberty, Philippe C; Shaik, Sason

    2009-01-01

    To characterize the nature of bonding we derive the topological properties of the electron charge density of a variety of bonds based on ab initio valence bond methods. The electron density and its associated Laplacian are partitioned into covalent, ionic, and resonance components in the valence bond spirit. The analysis provides a density-based signature of bonding types and reveals, along with the classical covalent and ionic bonds, the existence of two-electron bonds in which most of the bonding arises from the covalent-ionic resonance energy, so-called charge-shift bonds. As expected, the covalent component of the Laplacian at the bond critical point is found to be largely negative for classical covalent bonds. In contrast, for charge-shift bonds, the covalent part of the Laplacian is small or positive, in agreement with the weakly attractive or repulsive character of the covalent interaction in these bonds. On the other hand, the resonance component of the Laplacian is always negative or nearly zero, and it increases in absolute value with the charge-shift character of the bond, in agreement with the decrease of kinetic energy associated with covalent-ionic mixing. A new interpretation of the topology of the total density at the bond critical point is proposed to characterize covalent, ionic, and charge-shift bonding from the density point of view.

  13. 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.

  14. The nature of electron correlation in a dissociating bond

    NASA Astrophysics Data System (ADS)

    Hollett, Joshua W.; McKemmish, Laura K.; Gill, Peter M. W.

    2011-06-01

    We have constructed the unrestricted Hartree-Fock (UHF), restricted Hartree-Fock (RHF), and full configuration interaction (FCI) position and momentum intracules and holes for HṡṡṡH at bond lengths R from 1 to 10 bohrs. We trace the recently discovered inversion of the UHF position hole at intermediate R to over-localization of the spin-orbitals, and support this by a correlation energy component analysis. The RHF and UHF momentum holes are found to be more complicated; however their features are explained through decomposition of electron correlation effects. The UHF momentum hole is also found to invert and exhibits interesting behavior at large R. The RHF (but not UHF) and FCI momentum intracules exhibit Young-type interference patterns related to recent double photoionization experiments. Our analyses yield the most comprehensive picture to date of the behavior of the electrons during homolytic bond fission.

  15. 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.

  16. Anharmonic dynamics of intramolecular hydrogen bonds driven by DNA breathing

    NASA Astrophysics Data System (ADS)

    Alexandrov, B. S.; Stanev, V. G.; Bishop, A. R.; Rasmussen, K. Ø.

    2012-12-01

    We study the effects of the anharmonic strand-separation dynamics of double-stranded DNA on the infrared spectra of the intramolecular base-pairing hydrogen bonds. Using the extended Peyrard-Bishop-Dauxois model for the DNA breathing dynamics coupled with the Lippincott-Schroeder potential for N-H⋯N and N-H⋯O hydrogen bonding, we identify a high-frequency (˜96 THz) feature in the infrared spectra. We show that this sharp peak arises as a result of the anharmonic base-pair breathing dynamics of DNA. In addition, we study the effects of friction on the infrared spectra. For higher temperatures (˜300 K), where the anharmonicity of DNA dynamics is pronounced, the high-frequency peak is always present irrespective of the friction strength.

  17. 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.

  18. 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…

  19. 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 ...

  20. 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...

  1. 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.

  2. 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.

  3. 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…

  4. 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…

  5. Double Helix Revisited.

    ERIC Educational Resources Information Center

    Glickstein, Neil M.

    1995-01-01

    Describes the use of James Watson's book, "The Double Helix," as a multidisciplinary way of introducing students to actual science; the scientific method; dilemmas encountered in the world of research; and the rich setting of personalities, politics, and history in post-World War II Europe. (MKR)

  6. 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…

  7. Halogen bonds in crystal engineering: like hydrogen bonds yet different.

    PubMed

    Mukherjee, Arijit; Tothadi, Srinu; Desiraju, Gautam R

    2014-08-19

    The halogen bond is an attractive interaction in which an electrophilic halogen atom approaches a negatively polarized species. Short halogen atom contacts in crystals have been known for around 50 years. Such contacts are found in two varieties: type I, which is symmetrical, and type II, which is bent. Both are influenced by geometric and chemical considerations. Our research group has been using halogen atom interactions as design elements in crystal engineering, for nearly 30 years. These interactions include halogen···halogen interactions (X···X) and halogen···heteroatom interactions (X···B). Many X···X and almost all X···B contacts can be classified as halogen bonds. In this Account, we illustrate examples of crystal engineering where one can build up from previous knowledge with a focus that is provided by the modern definition of the halogen bond. We also comment on the similarities and differences between halogen bonds and hydrogen bonds. These interactions are similar because the protagonist atoms-halogen and hydrogen-are both electrophilic in nature. The interactions are distinctive because the size of a halogen atom is of consequence when compared with the atomic sizes of, for example, C, N, and O, unlike that of a hydrogen atom. Conclusions may be drawn pertaining to the nature of X···X interactions from the Cambridge Structural Database (CSD). There is a clear geometric and chemical distinction between type I and type II, with only type II being halogen bonds. Cl/Br isostructurality is explained based on a geometric model. In parallel, experimental studies on 3,4-dichlorophenol and its congeners shed light on the nature of halogen···halogen interactions and reveal the chemical difference between Cl and Br. Variable temperature studies also show differences between type I and type II contacts. In terms of crystal design, halogen bonds offer a unique opportunity in the strength, atom size and interaction gradation; this may be

  8. Memory, double, shadow, and evil.

    PubMed

    McNamara, P

    1994-04-01

    In order to examine shadow dynamics the author explores the phenomenology and mythological associations of the 'double' or Doppelgänger. Current Jungian-inspired theories concerning relations of shadow and double are found to be limited because they do not explain (1) the process of personification of the psychic complex which gives rise to the double, (2) the immediate conditions under which doubling occurs, (3) the conditions which lead to the assignment of evil qualities to the double as shadow. The paper seeks to remedy each of the above limitations by redescribing shadow/double phenomena in terms of autonomous memory phenomena, both personal and trans-personal.

  9. 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.

  10. 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.

  11. 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.

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 7 CFR 1726.27 - Contractor's bonds.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Contractor's bonds. 1726.27 Section 1726.27... AGRICULTURE ELECTRIC SYSTEM CONSTRUCTION POLICIES AND PROCEDURES General § 1726.27 Contractor's bonds. (a) RUS Form 168b, Contractor's Bond, shall be used when a contractor's bond is required by RUS Forms 200,...

  18. 27 CFR 25.96 - Superseding bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 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. 27 CFR 25.96 - Superseding bond.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 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,...

  20. 27 CFR 26.69 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Liquors and Articles in Puerto Rico Bonds § 26.69 Strengthening bonds. In all cases where the penal sum of... surety to attain a sufficient penal sum, or give a new bond to cover the entire liability. Strengthening... penal sum. Strengthening bonds shall show the current date of execution and the effective date....

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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.

  7. Hydrogen-bonded clusters of ferrocenecarboxylic acid on Au(111).

    PubMed

    Quardokus, Rebecca C; Wasio, Natalie A; Christie, John A; Henderson, Kenneth W; Forrest, Ryan P; Lent, Craig S; Corcelli, Steven A; Kandel, S Alex

    2014-09-14

    Self-assembled monolayers of ferrocenecarboxylic acid (FcCOOH) contain two fundamental units, both stabilized by intermolecular hydrogen bonding: dimers and cyclic five-membered catemers. At surface coverages below a full monolayer, however, there is a significantly more varied structure that includes double-row clusters containing two to twelve FcCOOH molecules. Statistical analysis shows a distribution of cluster sizes that is sharply peaked compared to a binomial distribution. This rules out simple nucleation-and-growth mechanisms of cluster formation, and strongly suggests that clusters are formed in solution and collapse into rows when deposited on the Au(111) surface.

  8. Substituent Directed Phototransformations of BN-Heterocycles: Elimination vs Isomerization via Selective B-C Bond Cleavage.

    PubMed

    Yang, Deng-Tao; Mellerup, Soren K; Peng, Jin-Bao; Wang, Xiang; Li, Quan-Song; Wang, Suning

    2016-09-14

    Electron-rich and -poor BN-heterocycles with benzyl-pyridyl backbones and two bulky aryls on the boron (Ar = tipp, BN-1, Ar = MesF, BN-2) have been found to display distinct molecular transformations upon irradiation by UV light. BN-1 undergoes an efficient photoelimination reaction forming a BN-phenanthrene with ΦPE = 0.25, whereas BN-2 undergoes a thermally reversible, stereoselective, and quantitative isomerization to a dark colored BN-1,3,5-cyclooctatriene (BN-1,3,5-COT, BN-2a). This unusual photoisomerization persists for other BN-heterocycles with electron-deficient aryls such as BN-3 with a benzyl-benzothiazolyl backbone and Mes(F) substituents or BN-4 with a benzyl-pyridyl backbone and two C6F5 groups on the boron. The photoisomerization of BN-4 goes beyond BN-1,3,5-COT (BN-4a), forming a new species (BN-1,3,6-COT, BN-4b) via C-F bond cleavage and [1,3]-F atom sigmatropic migration. Computational studies support that BN-4a is an intermediate in the formation of BN-4b. This work establishes that steric and electronic factors can effectively control the transformations of BN-heterocycles, allowing access to important and previously unknown BN-embedded species.

  9. Benchmarking DFT methods with small basis sets for the calculation of halogen-bond strengths.

    PubMed

    Siiskonen, Antti; Priimagi, Arri

    2017-02-01

    In recent years, halogen bonding has become an important design tool in crystal engineering, supramolecular chemistry and biosciences. The fundamentals of halogen bonding have been studied extensively with high-accuracy computational methods. Due to its non-covalency, the use of triple-zeta (or larger) basis sets is often recommended when studying halogen bonding. However, in the large systems often encountered in supramolecular chemistry and biosciences, large basis sets can make the calculations far too slow. Therefore, small basis sets, which would combine high computational speed and high accuracy, are in great demand. This study focuses on comparing how well density functional theory (DFT) methods employing small, double-zeta basis sets can estimate halogen-bond strengths. Several methods with triple-zeta basis sets are included for comparison. Altogether, 46 DFT methods were tested using two data sets of 18 and 33 halogen-bonded complexes for which the complexation energies have been previously calculated with the high-accuracy CCSD(T)/CBS method. The DGDZVP basis set performed far better than other double-zeta basis sets, and it even outperformed the triple-zeta basis sets. Due to its small size, it is well-suited to studying halogen bonding in large systems.

  10. Three methods to measure RH bond energies

    NASA Astrophysics Data System (ADS)

    Berkowitz, Joseph; Ellison, G. Barney; Gutman, David

    1993-03-01

    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.

  11. 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.

  12. Halogen Bonding in Organic Synthesis and Organocatalysis.

    PubMed

    Bulfield, David; Huber, Stefan M

    2016-10-04

    Halogen bonding is a noncovalent interaction similar to hydrogen bonding, which is based on electrophilic halogen substituents. Hydrogen-bonding-based organocatalysis is a well-established strategy which has found numerous applications in recent years. In light of this, halogen bonding has recently been introduced as a key interaction for the design of activators or organocatalysts that is complementary to hydrogen bonding. This Concept features a discussion on the history and electronic origin of halogen bonding, summarizes all relevant examples of its application in organocatalysis, and provides an overview on the use of cationic or polyfluorinated halogen-bond donors in halide abstraction reactions or in the activation of neutral organic substrates.

  13. Medieval orality, mothers, and bonding.

    PubMed

    Schwartz, Scott C

    2004-01-01

    The role of women in the Middle Ages was vilification, veneration, and exclusion. Due to the high rates of maternal and infant mortality bonding shifted from the mother-child dyad to one in which the Church, Holy Family, and king acted as pseudo-parents. In art this is suggested by the virtual absence of eye contact between the Virgin and Christ-child. Frustration of early oral needs consequent to lack of adequate mother-child bonding prompted a reactive emphasis on orality in art and legend. A decrease in infant mortality and a reciprocal improvement in mother child bonding contributed to cultural shifts in how self-realization would be accomplished during the Renaissance and in the later emergence of secular humanism.

  14. 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…

  15. 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).

  16. 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…

  17. Phosphate-Bonded Fly Ash.

    DTIC Science & Technology

    1994-12-09

    FCODE OC ______________ ARLINGTON VA 22217-5660 - dis~bu~i.19~ 3 B Navy Case No. 75,787 PATENTS PHOSPHATE -BONDED FLY ASH IN’NA G. TALMY DEBORAH A. HAUGHT...2 3 , CaO. MgO, etc. with which the H.PO4 reacts to form the polymer-like phosphate bonds which hold the fly ash particles together. In the second...conventional means. The moisture (water) content of the aqueous HP0 4 /fly ash mixture is preferably from about 3 to about 5 weight percent for semidry

  18. 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.

  19. 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.

  20. 27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 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...

  1. 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...

  2. 27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 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...

  3. 27 CFR 19.162 - Operations bond for distilled spirits plant and adjacent bonded wine cellar.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 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...

  4. 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.

  5. Algebra of Majorana doubling.

    PubMed

    Lee, Jaehoon; Wilczek, Frank

    2013-11-27

    Motivated by the problem of identifying Majorana mode operators at junctions, we analyze a basic algebraic structure leading to a doubled spectrum. For general (nonlinear) interactions the emergent mode creation operator is highly nonlinear in the original effective mode operators, and therefore also in the underlying electron creation and destruction operators. This phenomenon could open up new possibilities for controlled dynamical manipulation of the modes. We briefly compare and contrast related issues in the Pfaffian quantum Hall state.

  6. 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.

  7. The selective activation of a C-F bond with an auxiliary strong Lewis acid: a method to change the activation preference of C-F and C-H bonds.

    PubMed

    Wang, Lin; Sun, Hongjian; Li, Xiaoyan; Fuhr, Olaf; Fenske, Dieter

    2016-11-15

    The selective activation of the C-F bonds in substituted (2,6-difluorophenyl)phenylimines (2,6-F2H3C6-(C[double bond, length as m-dash]NH)-n'-R-C6H4 (n' = 2, R = H (1); n' = 2, R = Me (2); n' = 4, R = tBu (3))) by Fe(PMe3)4 with an auxiliary strong Lewis acid (LiBr, LiI, or ZnCl2) was explored. As a result, iron(ii) halides ((H5C6-(C[double bond, length as m-dash]NH)-2-FH3C6)FeX(PMe3)3 (X = Br (8); Cl (9)) and (n-RH4C6-(C[double bond, length as m-dash]NH)-2'-FH3C6)FeX(PMe3)3 (n = 2, R = Me, X = Br (11); n = 4, R = tBu, X = I (12))) were obtained. Under similar reaction conditions, using LiBF4 instead of LiBr or ZnCl2, the reaction of (2,6-difluorophenyl)phenylimine with Fe(PMe3)4 afforded an ionic complex [(2,6-F2H3C6-(C[double bond, length as m-dash]NH)-H4C6)Fe(PMe3)4](BF4) (10) via the activation of a C-H bond. The method of C-F bond activation with an auxiliary strong Lewis acid is appropriate for monofluoroarylmethanimines. Without the Lewis acid, iron(ii) hydrides ((2-RH4C6-(C[double bond, length as m-dash]NH)-2'-FH3C6)FeH(PMe3)3 (R = H (13); Me (14))) were generated from the reactions of Fe(PMe3)4 with the monofluoroarylmethanimines (2-FH4C6-(C[double bond, length as m-dash]NH)-2'-RC6H4 (R = H (4); Me (5))); however, in the presence of ZnCl2 or LiBr, iron(ii) halides ((2-RH4C6-(C[double bond, length as m-dash]NH)-H4C6)FeX(PMe3)3 (R = H, X = Cl (15); R = Me, X = Br (16))) could be obtained through the activation of a C-F bond. Furthermore, a C-F bond activation with good regioselectivity in (pentafluorophenyl)arylmethanimines (F5C6-(C[double bond, length as m-dash]NH)-2,6-Y2C6H3 (Y = F (6); H (7))) could be realized in the presence of ZnCl2 to produce iron(ii) chlorides ((2,6-Y2H3C6-(C[double bond, length as m-dash]NH)-F4C6)FeCl(PMe3)3 (Y = F (17); H (18))). This series of iron(ii) halides could be used to catalyze the hydrosilylation reaction of aldehydes. Due to the stability of iron(ii) halides to high temperature, the reaction mixture was allowed to be

  8. 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

  9. 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

  10. Dinuclear Calcium Complexes with Intramolecularly NH.O Hydrogen-Bonded Dicarboxylate Ligands.

    PubMed

    Ueyama, Norikazu; Takeda, Jiro; Yamada, Yusuke; Onoda, Akira; Okamura Ta, Taka-aki; Nakamura, Akira

    1999-02-08

    A novel dinuclear calcium complex, [Ca(2){(2-OCO-3-CH(3)C(6)H(3)NHCO)(2)C(CH(3))(2)}(2)(CH(3)OH)(6)] (1), was synthesized as a structural model of 8-coordinated Ca(II) ions in the double calcium-binding site of thermolysin. The complex has four NH.O hydrogen bonds between the amide NH and the carboxylate oxygen anion. Two types of bridging coordination of the carboxylate ligand to Ca(II) were found in 1. The amide NH forms a strong NH.O hydrogen bond with the anionic oxygen of the two carboxylate oxygens. A ligand-exchange reaction between the dinuclear calcium complex and eight equimolar amounts of 2,4,6-trimethylbenzoic acid or 2-CH(3)-6-t-BuCONHC(6)H(3)COOH indicates that the NH.O hydrogen bond prevents the dissociation of the Ca-O bond.

  11. Capillary flow weld-bonding

    NASA Technical Reports Server (NTRS)

    Vaughan, R. W.; Jones, R. J. (Inventor)

    1976-01-01

    The invention of a weld-bonding technique for titanium plates was described. This involves fastening at least two plates of titanium together using spot-welding and applying a bead of adhesive along the edge of the resistance spot-welded joint which upon heating, flows and fills the separation between the joint components.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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…

  17. 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

  18. 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.

  19. 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

  20. Effect of moisture, saliva, and blood contamination on the shear bond strength of brackets bonded with a conventional bonding system and self-etched bonding system

    PubMed Central

    Prasad, Mandava; Mohamed, Shamil; Nayak, Krishna; Shetty, Sharath Kumar; Talapaneni, Ashok Kumar

    2014-01-01

    Background: The success of bonding brackets to enamel with resin bonding systems is negatively affected by contamination with oral fluids such as blood and saliva. The new self-etch primer systems combine conditioning and priming agents into a single application, making the procedure more cost effective. Objective: The purpose of the study was to investigate the effect of moisture, saliva and blood contamination on shear bond strength of orthodontic brackets bonded with conventional bonding system and self-etch bonding system. Materials and Methods: Each system was examined under four enamel surface conditions (dry, water, saliva, and blood), and 80 human teeth were divided into two groups with four subgroups each of 10 according to enamel surface condition. Group 1 used conventional bonding system and Group 2 used self-etched bonding system. Subgroups 1a and 2a under dry enamel surface conditions; Subgroups 1b and 2b under moist enamel surface condition; Subgroups 3a and 3b under saliva enamel surface condition and Subgroup 4a and 4b under blood enamel surface condition. Brackets were bonded, and all the samples were then submitted to a shear bond test with a universal testing machine with a cross head speed of 1mm/sec. Results: The results showed that the contamination reduced the shear bond strength of all groups. In self-etch bonding system water and saliva had significantly higher bond strength when compared to other groups. Conclusion: It was concluded that the blood contamination showed lowest bond strength from both bonding systems. Self-etch bonding system resulted in higher bond strength than conventional bonding system under all conditions except the dry enamel surface. PMID:24678210

  1. 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.

  2. The effect of nitrogen incorporation on the bonding structure of hydrogenated carbon nitride films

    SciTech Connect

    Camero, M.; Buijnsters, J. G.; Gomez-Aleixandre, C.; Gago, R.; Caretti, I.; Jimenez, I.

    2007-03-15

    This work describes the composition and bonding structure of hydrogenated carbon nitride (a-CN{sub x}:H) films synthesized by electron cyclotron resonance chemical vapor deposition using as precursor gases argon, methane, and nitrogen. The composition of the films was derived from Rutherford backscattering and elastic recoil detection analysis and the bonding structure was examined by infrared (IR) spectroscopy and x-ray absorption near edge spectroscopy (XANES). By varying the nitrogen to methane ratio in the applied gas mixture, polymeric a-CN{sub x}:H films with N/C contents varying from 0.06 to 0.49 were obtained. Remarkably, the H content of the films ({approx}40 at. %) was rather unaffected by the nitrogenation process. The different bonding states as detected in the measured XANES C(1s) and N(1s) spectra have been correlated with those of a large number of reference samples. The XANES and IR spectroscopy results indicate that N atoms are efficiently incorporated into the amorphous carbon network and can be found in different bonding environments, such as pyridinelike, graphitelike, nitrilelike, and amino groups. The nitrogenation of the films results in the formation of N-H bonding environments at the cost of C-H structures. Also, the insertion of N induces a higher fraction of double bonds in the structure at the expense of the linear polymerlike chains, hence resulting in a more cross-linked solid. The formation of double bonds takes place through complex C=N structures and not by formation of graphitic aromatic rings. Also, the mechanical and tribological properties (hardness, friction, and wear) of the films have been studied as a function of the nitrogen content. Despite the major modifications in the bonding structure with nitrogen uptake, no significant changes in these properties are observed.

  3. Accurate bond energies of biodiesel methyl esters from multireference averaged coupled-pair functional calculations.

    PubMed

    Oyeyemi, Victor B; Keith, John A; Carter, Emily A

    2014-09-04

    Accurate bond dissociation energies (BDEs) are important for characterizing combustion chemistry, particularly the initial stages of pyrolysis. Here we contribute to evaluating the thermochemistry of biodiesel methyl ester molecules using ab initio BDEs derived from a multireference averaged coupled-pair functional (MRACPF2)-based scheme. Having previously validated this approach for hydrocarbons and a variety of oxygenates, herein we provide further validation for bonds within carboxylic acids and methyl esters, finding our scheme predicts BDEs within chemical accuracy (i.e., within 1 kcal/mol) for these molecules. Insights into BDE trends with ester size are then analyzed for methyl formate through methyl crotonate. We find that the carbonyl group in the ester moiety has only a local effect on BDEs. C═C double bonds in ester alkyl chains are found to increase the strengths of bonds adjacent to the double bond. An important exception are bonds beta to C═C or C═O bonds, which produce allylic-like radicals upon dissociation. The observed trends arise from different degrees of geometric relaxation and resonance stabilization in the radicals produced. We also compute BDEs in various small alkanes and alkenes as models for the long hydrocarbon chain of actual biodiesel methyl esters. We again show that allylic bonds in the alkenes are much weaker than those in the small methyl esters, indicating that hydrogen abstractions are more likely at the allylic site and even more likely at bis-allylic sites of alkyl chains due to more electrons involved in π-resonance in the latter. Lastly, we use the BDEs in small surrogates to estimate heretofore unknown BDEs in large methyl esters of biodiesel fuels.

  4. Chemical Bonding of Polymer on Carbon Nanotube

    DTIC Science & Technology

    2001-04-01

    vetIcal displacement of CNT z dl:streched length of C-C bond in polymer .Z dLI: streching of C-C bond within polymer SdL2: streched length Of C-C...bond at interface - dL2: streching of C-C bond at intedace of B of polymer/CNT ’ n polymer-CNT at first bonding site E 1 1 I dL3: streching of C-C bond

  5. 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.

  6. 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.

  7. 76 FR 14746 - Surety Companies Acceptable on Federal Bonds Change in State of Incorporation; Western Bonding...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-17

    ... Bonding Company; Western Insurance Company AGENCY: Financial Management Service, Fiscal Service... Bonding Company (NAIC 13191) and Western Insurance Company (NAIC 10008) have redomesticated from the...

  8. Boron as an Electron-Pair Donor for B⋅⋅⋅Cl Halogen Bonds.

    PubMed

    Alkorta, Ibon; Elguero, José; Del Bene, Janet E

    2016-10-05

    MP2/aug'-cc-pVTZ calculations were performed to investigate boron as an electron-pair donor in halogen-bonded complexes (CO)2 (HB):ClX and (N2 )2 (HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH3 , and H. Equilibrium halogen-bonded complexes with boron as the electron-pair donor are found on all of the potential surfaces, except for (CO)2 (HB):ClCH3 and (N2 )2 (HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO)2 (HB):ClF, (CO)2 (HB):ClCl, (N2 )2 (HB):ClCl, and (N2 )2 (HB):ClOH, which are stabilized by chlorine-shared halogen bonds. These complexes have increased binding energies and shorter B-Cl distances. Charge transfer stabilizes all complexes and occurs from the B lone pair to the σ* Cl-A orbital of ClX, in which A is the atom of X directly bonded to Cl. A second reduced charge-transfer interaction occurs in (CO)2 (HB):ClX complexes from the Cl lone pair to the π* C≡O orbitals. Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) spin-spin coupling constants, (1x) J(B-Cl), across the halogen bonds are also indicative of the changing nature of this bond. (1x) J(B-Cl) values for both series of complexes are positive at long distances, increase as the distance decreases, and then decrease as the halogen bonds change from traditional to chlorine-shared bonds, and begin to approach the values for the covalent bonds in the corresponding ions [(CO)2 (HB)-Cl](+) and [(N2 )2 (HB)-Cl](+) . Changes in (11) B chemical shieldings upon complexation correlate with changes in the charges on B.

  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. Regulation of actin catch-slip bonds with a RhoA-formin module

    PubMed Central

    Lee, Cho-yin; Lou, Jizhong; Wen, Kuo-Kuang; McKane, Melissa; Eskin, Suzanne G.; Rubenstein, Peter A.; Chien, Shu; Ono, Shoichiro; Zhu, Cheng; McIntire, Larry V.

    2016-01-01

    The dynamic turnover of the actin cytoskeleton is regulated cooperatively by force and biochemical signaling. We previously demonstrated that actin depolymerization under force is governed by catch-slip bonds mediated by force-induced K113:E195 salt-bridges. Yet, the biochemical regulation as well as the functional significance of actin catch bonds has not been elucidated. Using AFM force-clamp experiments, we show that formin controlled by RhoA switches the actin catch-slip bonds to slip-only bonds. SMD simulations reveal that the force does not induce the K113:E195 interaction when formin binds to actin K118 and E117 residues located at the helical segment extending to K113. Actin catch-slip bonds are suppressed by single residue replacements K113E and E195K that interrupt the force-induced K113:E195 interaction; and this suppression is rescued by a K113E/E195K double mutant (E/K) restoring the interaction in the opposite orientation. These results support the biological significance of actin catch bonds, as they corroborate reported observations that RhoA and formin switch force-induced actin cytoskeleton alignment and that either K113E or E195K induces yeast cell growth defects rescued by E/K. Our study demonstrates how the mechano-regulation of actin dynamics is modulated by biochemical signaling molecules, and suggests that actin catch bonds may be important in cell functions. PMID:27731359

  11. Regulation of actin catch-slip bonds with a RhoA-formin module

    NASA Astrophysics Data System (ADS)

    Lee, Cho-Yin; Lou, Jizhong; Wen, Kuo-Kuang; McKane, Melissa; Eskin, Suzanne G.; Rubenstein, Peter A.; Chien, Shu; Ono, Shoichiro; Zhu, Cheng; McIntire, Larry V.

    2016-10-01

    The dynamic turnover of the actin cytoskeleton is regulated cooperatively by force and biochemical signaling. We previously demonstrated that actin depolymerization under force is governed by catch-slip bonds mediated by force-induced K113:E195 salt-bridges. Yet, the biochemical regulation as well as the functional significance of actin catch bonds has not been elucidated. Using AFM force-clamp experiments, we show that formin controlled by RhoA switches the actin catch-slip bonds to slip-only bonds. SMD simulations reveal that the force does not induce the K113:E195 interaction when formin binds to actin K118 and E117 residues located at the helical segment extending to K113. Actin catch-slip bonds are suppressed by single residue replacements K113E and E195K that interrupt the force-induced K113:E195 interaction; and this suppression is rescued by a K113E/E195K double mutant (E/K) restoring the interaction in the opposite orientation. These results support the biological significance of actin catch bonds, as they corroborate reported observations that RhoA and formin switch force-induced actin cytoskeleton alignment and that either K113E or E195K induces yeast cell growth defects rescued by E/K. Our study demonstrates how the mechano-regulation of actin dynamics is modulated by biochemical signaling molecules, and suggests that actin catch bonds may be important in cell functions.

  12. 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.

  13. Does silica surface catalyse peptide bond formation? New insights from first-principles calculations.

    PubMed

    Rimola, Albert; Tosoni, Sergio; Sodupe, Mariona; Ugliengo, Piero

    2006-01-16

    The role that silica surface could have played in prebiotic chemistry as a catalyst for peptide bond formation has been addressed at the B3LYP/6-31+G(d,p) level for a model reaction involving glycine and ammonia on a silica cluster mimicking an isolated terminal silanol group present at the silica surface. Hydrogen-bond complexation between glycine and the silanol is followed by the formation of the mixed surface anhydride Si(surf)-O-C(=O)-R, which has been suggested in the literature to activate the C=O bond towards nucleophilic attack by a second glycine molecule, here simulated by the simpler NH3 molecule. However, B3LYP/6-31+G(d,p) calculations show that formation of the surface mixed anhydride Si(surf)-O-C(=O)-R is disfavoured (delta(r)G298 approximately 6 kcal mol(-1)), and that the surface bond only moderately lowers the free-energy barrier of the nucleophilic attack responsible for peptide bond formation (deltaG298(double dagger) approximately 48 kcal mol(-1)) in comparison with the uncatalysed reaction (deltaG298(double dagger) approximately 52 kcal mol(-1)). A further decrease of the free-energy barrier of peptide bond formation (deltaG298(double dagger) approximately 41 kcal mol(-1)) is achieved by a single water molecule close to the reaction centre acting as a proton-transfer helper in the activated complex. A possible role of strained silica surface defects on the formation of the surface mixed anhydride Si(surf)-O-C(=O)-R has also been addressed.

  14. Experimental Characterisation and Multi-Physic Modelling of Direct Bonding Mechanical Behaviour: Application to Spatial Optical Systems

    NASA Astrophysics Data System (ADS)

    Cocheteau, N.; Maurel-Pantel, A.; Lebon, F.; Rosu, I.; Ait-Zaid, S.; Savin de Larclause, I.; Salaun, Y.

    2014-06-01

    Direct bonding is a well-known process. However in order to use this process in spatial instrument fabrication the mechanical resistance needs to be quantified precisely. In order to improve bonded strength, optimal parameters of the process are found by studying the influence of annealing time, temperature and roughness which are studied using three experimental methods: double shear, cleavage and wedge tests. Those parameters are chosen thanks to the appearance of time/temperature equivalence. All results brought out the implementation of a multi-physic model to predict the mechanical behavior of direct bonding interface.

  15. 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.

  16. 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.

  17. 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)

  18. 'Love Hormone' Helps Dads and Babies Bond

    MedlinePlus

    ... page: https://medlineplus.gov/news/fullstory_163657.html 'Love Hormone' Helps Dads and Babies Bond Brain scans ... 2017 FRIDAY, Feb. 17, 2017 (HealthDay News) -- The "love hormone" oxytocin may program fathers to bond with ...

  19. 25 CFR 214.4 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... MINING, EXCEPT OIL AND GAS § 214.4 Bonds. Lessee shall furnish with each lease at the time it is filed... consent of the Indian landowner may authorize a bond for a lesser amount if, in his opinion,...

  20. 25 CFR 214.4 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... MINING, EXCEPT OIL AND GAS § 214.4 Bonds. Lessee shall furnish with each lease at the time it is filed... consent of the Indian landowner may authorize a bond for a lesser amount if, in his opinion,...

  1. 29 CFR 501.9 - Surety bond.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) The bond must be payable to the Administrator, Wage and Hour Division, United States Department of Labor, 200 Constitution Avenue, NW., Room S-3502, Washington, DC 20210. The bond must obligate...

  2. 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.

  3. 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.

  4. 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)

  5. 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.

  6. Double Eclipsing Binary Fitting

    NASA Astrophysics Data System (ADS)

    Cagas, P.; Pejcha, O.

    2012-06-01

    The parameters of the mutual orbit of eclipsing binaries that are physically connected can be obtained by precision timing of minima over time through light travel time effect, apsidal motion or orbital precession. This, however, requires joint analysis of data from different sources obtained through various techniques and with insufficiently quantified uncertainties. In particular, photometric uncertainties are often underestimated, which yields too small uncertainties in minima timings if determined through analysis of a χ2 surface. The task is even more difficult for double eclipsing binaries, especially those with periods close to a resonance such as CzeV344, where minima get often blended with each other. This code solves the double binary parameters simultaneously and then uses these parameters to determine minima timings (or more specifically O-C values) for individual datasets. In both cases, the uncertainties (or more precisely confidence intervals) are determined through bootstrap resampling of the original data. This procedure to a large extent alleviates the common problem with underestimated photometric uncertainties and provides a check on possible degeneracies in the parameters and the stability of the results. While there are shortcomings to this method as well when compared to Markov Chain Monte Carlo methods, the ease of the implementation of bootstrapping is a significant advantage.

  7. Firewalls from double purity

    NASA Astrophysics Data System (ADS)

    Bousso, Raphael

    2013-10-01

    The firewall paradox is often presented as arising from double entanglement, but I argue that more generally the paradox is double purity. Near-horizon modes are purified by the interior, in the infalling vacuum. Hence, they cannot also be pure alone, or in combination with any third system, as demanded by unitarity. This conflict arises independently of the Page time, for entangled and for pure states. It implies that identifications of Hilbert spaces cannot resolve the paradox. Traditional complementarity requires the unitary identification of infalling matter with a scrambled subsystem of the Hawking radiation. Extending this map to the infalling vacuum overdetermines the out-state. More general complementarity maps (“A=RB,” “ER=EPR”) necessarily fail when the near-horizon zone is pure. I argue that pure-zone states span the microcanonical ensemble, and that this suffices to make the horizon a special place. I advocate that the ability to detect the horizon locally, rather than the degree or probability of violence, is what makes firewalls problematic. Conversely, if the production of matter at the horizon can be dynamically understood and shown to be consistent, then firewalls do not constitute a violation of the equivalence principle.

  8. Durability of Adhesively Bonded Structure

    DTIC Science & Technology

    1992-08-11

    frequently. Significant technology improvements have occurred In surface treatment, primers, joint analyses, adhesives and process controls. These have...clearly established the Initial cost savings potential for adhesive bonding. While this approach addresses the adequacy of joints early in service, there...processes with those changes which occur as a result of residual stress or cyclic loading in the adhesive joint 074-2R-bh 1 To fill a small part of this

  9. 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.

  10. 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.

  11. H bonds in astrophysical ices

    NASA Astrophysics Data System (ADS)

    Palumbo, M. E.; Baratta, G. A.; Leto, G.; Strazzulla, G.

    2010-05-01

    We have studied, by infrared absorption spectroscopy, the profile (shape and peak position) of the OH dangling bond feature in pure porous amorphous solid water (ASW) and in mixtures of water with other species (CO, CO2, O2, N2, H2O2, CH4, SO2, and CH3OH) at 12-16 K. Furthermore, we have investigated the effects of ion and UV irradiation on the morphology/porosity of amorphous water ice. Thin films (about 0.25 - 1 micrometer) of porous amorphous water ice were irradiated with 200 keV H+, 30 keV He+, and 10.2 eV Lyman al pha photons at 12-16 K. We have found that the profile of the OH dangling bond feature depends on the mixture considered and that the intensity of the OH dangling bond feature decreases after irradiation. This latter result indicates that the porosity of amorphous water ice decreases after both ion and UV irradiation.

  12. Evaluation of Shear Bond Strength of Newer Bonding Systems on Superficial and Deep Dentin

    PubMed Central

    Kumari, R Veena; Siddaraju, Kishore; Nagaraj, Hema; Poluri, Ramya Krishna

    2015-01-01

    Background: The purpose of this study was to compare the shear bond strength of nanocomposite resin to superficial dentin and deep dentin using two different dentin bonding systems. Materials and Methods: All teeth were sectioned at various levels (superficial dentin: Dentin within 0.5-1 mm of dentinoenamel junction; deep dentin: Dentin within 0.5 mm of the highest pulp horn) using a Carborundum Disc and embedded in acrylic block of specific size. Selected specimens (60 premolar teeth) were grouped randomly into three groups, the groups were differentiated into superficial dentin, deep dentin, and control group which were further divided into sub Group A and Subgroup B containing 10 teeth each, depending on the bonding agents used. In Subgroup A, Tetric N Bond, and in Subgroup B Single Bond Universal were used. In the control group no bonding agent was used. The specimens were thermocycled for 500 cycles between 5°C and 55°C water bath for 40 s. Finally, the specimens were subjected to shear bond strength study under INSTRON machine (Universal Testing Machine). The maximum shear bond strengths were noted at the time of fracture (de-bonding) of the restorative material. Results were analyzed using ANOVA test, Bonferroni test, and paired t-test. Results: Bond strength values of fifth generation bonding system (Tetric N Bond) showed higher mean shear bond strength compared to seventh generation bonding system (Single Bond Universal). There was a significant fall in bond strength values as one reaches deeper levels of dentin from superficial to deep dentin. Conclusion: There was a significant difference between the bond strength of fifth generation bonding system (Tetric N Bond) and seventh generation bonding system (Single Bond Universal). Decrease in the bond strength values is seen for the deeper level of dentin as compared to superficial dentin. PMID:26435613

  13. Recovery of the wild type atomic flexibility in the HIV-1 protease double mutants.

    PubMed

    De Conto, Valderes; Braz, Antônio S K; Perahia, David; Scott, Luis P B

    2015-06-01

    The emergence of drug resistant mutations due to the selective pressure exerted by antiretrovirals, including protease inhibitors (PIs), remains a major problem in the treatment of AIDS. During PIs therapy, the occurrence of primary mutations in the wild type HIV-1 protease reduces both the affinity for the inhibitors and the viral replicative capacity compared to the wild type (WT) protein, but additional mutations compensate for this reduced viral fitness. To investigate this phenomenon from the structural point of view, we combined Molecular Dynamics and Normal Mode Analysis to analyze and compare the variations of the flexibility of C-alpha atoms and the differences in hydrogen bond (h-bond) network between the WT and double mutants. In most cases, the flexibility profile of the double mutants was more often similar to that of the WT than to that of the related single base mutants. All single mutants showed a significant alteration in h-bond formation compared to WT. Most of the significant changes occur in the border between the flap and cantilever regions. We found that all the considered double mutants have their h-bond pattern significantly altered in comparison to the respective single base mutants affecting their flexibility profile that becomes more similar to that of WT. This WT flexibility restoration in the double mutants appears as an important factor for the HIV-1 fitness recovery observed in patients.

  14. Full CI benchmark calculations on N2, NO, and O2 - A comparison of methods for describing multiple bonds

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1987-01-01

    Full configuration interaction (CI) calculations on the ground states of N2, NO, and O2 using a DZP Gaussian basis are compared with single-reference SDCI and coupled pair approaches (CPF), as well as with CASSCF multireference CI approaches. The CASSCF/MRCI technique is found to describe multiple bonds as well as single bonds. Although the coupled pair functional approach gave chemical accuracy (1 kcal/mol) for bonds involving hydrogen, larger errors occur in the CPF approach for the multiple bonded systems considered here. CI studies on the 1Sigma(g +) state of N2, including all single, double, triple, and quadruple excitations show that triple excitations are very important for the multiple bond case, and accounts for most of the deficiency in the coupled pair functional methods.

  15. The Muon F-µ+-F Hydrogen Bond-like Complex.

    PubMed

    Blinc, Robert; Lahajnar, Gojmir; Potočnik, Anton

    2011-09-01

    Muon spin rotation (µSR) and relaxation has been used to study the local magnetic structure of K3Fe5F15. A collinear F-µ+-F "hydrogen bond-like" symmetric double minimum type complex with a F...F distance of 2.8 Å and a separation between the two minima of 0.8 Å has been found in the paramagnetic phase. The apparent central position of the muon seems to be the result of fast muon tunneling between two equivalent minima in the F-µ+-F bond.

  16. Synthesis and Characterization of a Hyperbranched Hydrogen Bond Acidic Carbosilane Sorbent Polymer

    DTIC Science & Technology

    2010-01-01

    double bond of HCSA2 (1) electrophilically attacks the ketone carbon of the HFA. The bonds are formed via a pericyclic mechanism which requires formation...val- ues for H, 3.1% and C, 35.4% compared with the theoretical weight percents of H, 2.2%, and C, 34.3%. Fluorine composi- tion numbers were...Srcic, S. Acta Chim Solv 2004, 51, 373–394. 43 Bhadury, P. S.; Dubey, V.; Singh, S.; Saxena, C. J. Fluorine Chem 2005, 126, 1252–1256. 44 Grate, J. W

  17. Effortless way of bonding a lingual retainer.

    PubMed

    Pai, Vikram; Pai, Ramya; Revenkar, Ameet; Jasoria, Gaurav

    2013-01-01

    Post orthodontic treatment, retention is one of the most important step for prevention of relapse. Over the years many direct and indirect techniques for placing a bonded lingual retainer have been practiced clinically. Present clinical practice demands a much convenient and effortless technique for bonding a lingual retainer. This article describes a simplified technique of bonding a lingual retainer.

  18. 25 CFR 163.21 - Bonds required.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Bonds required. 163.21 Section 163.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER GENERAL FORESTRY REGULATIONS Forest Management and Operations § 163.21 Bonds required. (a) Performance bonds will be required in connection with...

  19. 25 CFR 163.21 - Bonds required.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Bonds required. 163.21 Section 163.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER GENERAL FORESTRY REGULATIONS Forest Management and Operations § 163.21 Bonds required. (a) Performance bonds will be required in connection with...

  20. 25 CFR 163.21 - Bonds required.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Bonds required. 163.21 Section 163.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER GENERAL FORESTRY REGULATIONS Forest Management and Operations § 163.21 Bonds required. (a) Performance bonds will be required in connection with...

  1. 25 CFR 163.21 - Bonds required.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Bonds required. 163.21 Section 163.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER GENERAL FORESTRY REGULATIONS Forest Management and Operations § 163.21 Bonds required. (a) Performance bonds will be required in connection with...

  2. 25 CFR 163.21 - Bonds required.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 25 Indians 1 2014-04-01 2014-04-01 false Bonds required. 163.21 Section 163.21 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER GENERAL FORESTRY REGULATIONS Forest Management and Operations § 163.21 Bonds required. (a) Performance bonds will be required in connection with...

  3. 43 CFR 3134.1 - Bonding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Bonding. 3134.1 Section 3134.1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bonding: General § 3134.1 Bonding. (a) Prior to issuance of an oil and gas lease, the successful...

  4. 43 CFR 3430.6-2 - Bonding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Bonding. 3430.6-2 Section 3430.6-2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT... Bonding. The lease bond for a preference right lease shall be set in accordance with subpart 3474 of...

  5. 30 CFR 57.12042 - Track bonding.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Track bonding. 57.12042 Section 57.12042 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... and Underground § 57.12042 Track bonding. Both rails shall be bonded or welded at every joint...

  6. 36 CFR 228.51 - Bonding.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 2 2011-07-01 2011-07-01 false Bonding. 228.51 Section 228... Mineral Materials General Provisions § 228.51 Bonding. (a) Bond requirements. Before operations may begin... noted in paragraphs (a) (1) and (3) of this section, where the authorized officer may waive such...

  7. 30 CFR 57.12042 - Track bonding.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Track bonding. 57.12042 Section 57.12042 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... and Underground § 57.12042 Track bonding. Both rails shall be bonded or welded at every joint...

  8. 36 CFR 228.51 - Bonding.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 2 2010-07-01 2010-07-01 false Bonding. 228.51 Section 228... Mineral Materials General Provisions § 228.51 Bonding. (a) Bond requirements. Before operations may begin... noted in paragraphs (a) (1) and (3) of this section, where the authorized officer may waive such...

  9. 43 CFR 3154.2 - Additional bonding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Additional bonding. 3154.2 Section 3154.2 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT... Requirements § 3154.2 Additional bonding. The authorized officer may increase the amount of any bond that...

  10. Cleanliness inspection tool for RSRM bond surfaces

    NASA Technical Reports Server (NTRS)

    Mattes, Robert A.

    1995-01-01

    Using optically stimulated electron emission (OSEE), Thiokol has monitored bond surfaces in process for contamination on the Redesigned Solid Rocket Motor (RSRM). This technique provides process control information to help assure bond surface quality and repeatability prior to bonding. This paper will describe OSEE theory of operation and the instrumentation implemented at Thiokol Corporation since 1987. Data from process hardware will be presented.

  11. 43 CFR 16.5 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Bonds. 16.5 Section 16.5 Public Lands: Interior Office of the Secretary of the Interior CONSERVATION OF HELIUM § 16.5 Bonds. The applicant shall be required to submit a bond in such amount and in such form as the Secretary may prescribe to...

  12. 43 CFR 16.5 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Bonds. 16.5 Section 16.5 Public Lands: Interior Office of the Secretary of the Interior CONSERVATION OF HELIUM § 16.5 Bonds. The applicant shall be required to submit a bond in such amount and in such form as the Secretary may prescribe to...

  13. 43 CFR 16.5 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Bonds. 16.5 Section 16.5 Public Lands: Interior Office of the Secretary of the Interior CONSERVATION OF HELIUM § 16.5 Bonds. The applicant shall be required to submit a bond in such amount and in such form as the Secretary may prescribe to...

  14. 36 CFR 223.35 - Performance bond.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 2 2010-07-01 2010-07-01 false Performance bond. 223.35 Section 223.35 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE SALE AND... Performance bond. Timber sale contracts may require the purchaser to furnish a performance bond...

  15. 43 CFR 23.9 - Performance bond.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Performance bond. 23.9 Section 23.9 Public... LANDS § 23.9 Performance bond. (a)(1) Upon approval of an exploration plan or mining plan, the operator shall be required to file a suitable performance bond of not less than $2,000 with satisfactory...

  16. 25 CFR 216.8 - Performance bond.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Performance bond. 216.8 Section 216.8 Indians BUREAU OF... RECLAMATION OF LANDS General Provisions § 216.8 Performance bond. (a) Upon approval of an exploration plan or mining plan, the operator shall be required to file a suitable performance bond of not less than...

  17. 43 CFR 23.9 - Performance bond.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Performance bond. 23.9 Section 23.9 Public... LANDS § 23.9 Performance bond. (a)(1) Upon approval of an exploration plan or mining plan, the operator shall be required to file a suitable performance bond of not less than $2,000 with satisfactory...

  18. 36 CFR 9.13 - Performance bond.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 1 2011-07-01 2011-07-01 false Performance bond. 9.13... MINERALS MANAGEMENT Mining and Mining Claims § 9.13 Performance bond. (a) Upon approval of a plan of operations the operator shall be required to file a suitable performance bond with satisfactory...

  19. 36 CFR 223.35 - Performance bond.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 2 2011-07-01 2011-07-01 false Performance bond. 223.35... Sale Contracts Contract Conditions and Provisions § 223.35 Performance bond. Timber sale contracts may require the purchaser to furnish a performance bond for satisfactory compliance with its terms....

  20. 25 CFR 216.8 - Performance bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Performance bond. 216.8 Section 216.8 Indians BUREAU OF... RECLAMATION OF LANDS General Provisions § 216.8 Performance bond. (a) Upon approval of an exploration plan or mining plan, the operator shall be required to file a suitable performance bond of not less than...