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Sample records for hg-s bond length

  1. Equilibrium CO bond lengths

    Science.gov (United States)

    Demaison, Jean; Császár, Attila G.

    2012-09-01

    Based on a sample of 38 molecules, 47 accurate equilibrium CO bond lengths have been collected and analyzed. These ultimate experimental (reEX), semiexperimental (reSE), and Born-Oppenheimer (reBO) equilibrium structures are compared to reBO estimates from two lower-level techniques of electronic structure theory, MP2(FC)/cc-pVQZ and B3LYP/6-311+G(3df,2pd). A linear relationship is found between the best equilibrium bond lengths and their MP2 or B3LYP estimates. These (and similar) linear relationships permit to estimate the CO bond length with an accuracy of 0.002 Å within the full range of 1.10-1.43 Å, corresponding to single, double, and triple CO bonds, for a large number of molecules. The variation of the CO bond length is qualitatively explained using the Atoms in Molecules method. In particular, a nice correlation is found between the CO bond length and the bond critical point density and it appears that the CO bond is at the same time covalent and ionic. Conditions which permit the computation of an accurate ab initio Born-Oppenheimer equilibrium structure are discussed. In particular, the core-core and core-valence correlation is investigated and it is shown to roughly increase with the bond length.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

  3. Bond length variation in hydronitride molecules and nitride crystals

    Science.gov (United States)

    Buterakos, L. A.; Gibbs, G. V.; Boisen, M. B.

    1992-08-01

    Bond lengths calculated for the coordination polyhedra in hydronitride molecules match average values observed for XN bonds involving main group X-cations in nitride crystals to within ˜0.04 Å. As suggested for oxide and sulfide molecules and crystals, the forces that determine the average bond lengths recorded for coordinated polyhedra in hydronitride molecules and nitride crystals appear to be governed in large part by the atoms that comprise the polyhedra and those that induce local charge balance. The forces exerted on the coordinated polyhedra by other parts of the structure seem to play a small if not an insignificant role in governing bond length variations. Bonded radii for the nitride ion obtained from theoretical electron density maps calculated for the molecules increase linearly with bond length as observed for nitride crystals with the rock salt structure. Promolecule radii calculated for the molecules correlate with bonded and ionic radii, indicating that the electron density distributions in hydronitride molecules possess a significant atomic component, despite bond type.

  4. Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals.

    Science.gov (United States)

    Gagné, Olivier Charles; Hawthorne, Frank Christopher

    2016-08-01

    Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: ([3])Li(+), ([3])Na(+), ([4])K(+), ([4])Rb(+), ([6])Cs(+), ([3])Be(2+), ([4])Mg(2+), ([6])Ca(2+), ([6])Sr(2+) and ([6])Ba(2+), but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of ([6])Na(+), the ratio Ueq(Na)/Ueq(bonded anions) is partially correlated with 〈([6])Na(+)-O(2-)〉 (R(2) = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li(+) in

  5. Correlation of Fe2+ isomer shifts with bond lengths and bond strengths in neso- and sorosilicates

    Institute of Scientific and Technical Information of China (English)

    李哲; E.DeGrave

    1995-01-01

    An evaluation of Mbssbauer isomer shift and quadrupole splitting data of Fe2+ in a number of structurally well characterized neso- and sorosilicates is presented. It is found that the nearly linear correlations exist both between the isomer shift and the bond length and between the isomer shift and the bond strength. These correlations are discussed on the basis of the variation of the s-electron density at the Fe2+ nuclei with the chemical bond characteristics.

  6. Variation of H 2 bond length with magnetic field

    Science.gov (United States)

    Misra, Anirban; Panda, Anirban

    2008-11-01

    We find a new effect, namely, the variation of the ratio of concentrations of ortho- and para-isomers of hydrogen in thermal equilibrium in a uniform external magnetic field with field strength and temperature, that can be observed experimentally. The observation can determine the variation of bond length with the magnetic field strength.

  7. Bond Length Dependence on Quantum States as Shown by Spectroscopy

    Science.gov (United States)

    Lim, Kieran F.

    2005-01-01

    A discussion on how a spreadsheet simulation of linear-molecular spectra could be used to explore the dependence of rotational band spacing and contours on average bond lengths in the initial and final quantum states is presented. The simulation of hydrogen chloride IR, iodine UV-vis, and nitrogen UV-vis spectra clearly show whether the average…

  8. Mean bond-length variation in crystal structures: a bond-valence approach.

    Science.gov (United States)

    Bosi, Ferdinando

    2014-08-01

    The distortion theorem of the bond-valence theory predicts that the mean bond length 〈D〉 increases with increasing deviation of the individual bond lengths from their mean value according to the equation 〈D〉 = (D' + ΔD), where D' is the length found in a polyhedron having equivalent bonds and ΔD is the bond distortion. For a given atom, D' is expected to be similar from one structure to another, whereas 〈D〉 should vary as a function of ΔD. However, in several crystal structures 〈D〉 significantly varies without any relevant contribution from ΔD. In accordance with bond-valence theory, 〈D〉 variation is described here by a new equation: 〈D〉 = (DRU + ΔDtop + ΔDiso + ΔDaniso + ΔDelec), where DRU is a constant related to the type of cation and coordination environment, ΔDtop is the topological distortion related to the way the atoms are linked, ΔDiso is an isotropic effect of compression (or stretching) in the bonds produced by steric strain and represents the same increase (or decrease) in all the bond lengths in the coordination sphere, ΔDaniso is the distortion produced by compression and stretching of bonds in the same coordination sphere, ΔDelec is the distortion produced by electronic effects. If present, ΔDelec can be combined with ΔDaniso because they lead to the same kind of distortions in line with the distortion theorem. Each D-index, in the new equation, corresponds to an algebraic expression containing experimental and theoretical bond valences. On the basis of this study, the ΔD index defined in bond valence theory is a result of both the bond topology and the distortion theorem (ΔD = ΔDtop + ΔDaniso + ΔDelec), and D' is a result of the compression, or stretching, of bonds (D' = DRU + ΔDiso). The deficiencies present in the bond-valence theory in explaining mean bond-length variations can therefore be overcome, and the observed variations of 〈D〉 in crystal structures can be

  9. Simple bond length dependence: A correspondence between reactive fluid theories

    Science.gov (United States)

    Dyer, Kippi M.; Perkyns, John S.; Pettitt, B. M.

    2005-06-01

    Two elementary models of reactive fluids are examined, the first being a standard construction assuming molecular dissociation at infinite separation; the second is an open mixture of nondissociative molecules and free atoms in which the densities of free atoms and molecules are coupled. An approximation to the density of molecules, to low order in site density, is derived in terms of the classical associating fluid theory variously described by Wertheim [J. Chem. Phys. 87, 7323 (1987)] and Stell [Physica A 231, 1 (1996)]. The results are derived for a fluid of dimerizing hard spheres, and predict dependence of the molecular density on the total site density, the hard sphere diameter, and the bond length of the dimer. The results for the two reactive models are shown to be qualitatively similar, and lead to equivalent predictions of the molecular density for the infinitely short and infinitely long bond lengths.

  10. Electron correlation and bond-length alternation in polyene chains

    Energy Technology Data Exchange (ETDEWEB)

    Kuprievich, V.A.

    1986-11-01

    The PPP model is used to consider polyene chains in the ground state with allowance for the interaction of the electrons with core deformations. The stationary wave functions describing the electron correlations are derived as antisymmetrized products of two-electron functions optimized with respect to all variational parameters. The bond-length alternation can be related to the characteristics of the electron-electron potential; one can allow approximately for the effects of interaction between electrons at adjacent centers on the alternation by renormalizing the parameters in the Hubbard model.

  11. The bond length and bond energy of gaseous CrW.

    Science.gov (United States)

    Matthew, Daniel J; Oh, Sang Hoon; Sevy, Andrew; Morse, Michael D

    2016-06-07

    Supersonically cooled CrW was studied using resonant two-photon ionization spectroscopy. The vibronically resolved spectrum was recorded over the region 21 100 to 23 400 cm(-1), showing a very large number of bands. Seventeen of these bands, across three different isotopologues, were rotationally resolved and analyzed. All were found to arise from the ground (1)Σ(+) state of the molecule and to terminate on states with Ω' = 0. The average r0 bond length across the three isotopic forms was determined to be 1.8814(4) Å. A predissociation threshold was observed in this dense manifold of vibronic states at 23 127(10) cm(-1), indicating a bond dissociation energy of D0(CrW) = 2.867(1) eV. Using the multiple bonding radius determined for atomic Cr in previous work, the multiple bonding radius for tungsten was calculated to be 1.037 Å. Comparisons are made between CrW and the previously investigated group 6 diatomic metals, Cr2, CrMo, and Mo2, and to previous computational studies of this molecule. It is also found that the accurately known bond dissociation energies of group 5/6 metal diatomics Cr2, V2, CrW, NbCr, VNb, Mo2, and Nb2 display a qualitative linear dependence on the sum of the d-orbital radial expectation values, r; this relationship allows the bond dissociation energies of other molecules of this type to be estimated.

  12. Bond-length fluctuations in the copper oxide superconductors

    CERN Document Server

    Goodenough, J B

    2003-01-01

    Superconductivity in the copper oxides occurs at a crossover from localized to itinerant electronic behaviour, a transition that is first order. A spinodal phase segregation is normally accomplished by atomic diffusion; but where it occurs at too low a temperature for atomic diffusion, it may be realized by cooperative atomic displacements. Locally cooperative, fluctuating atomic displacements may stabilize a distinguishable phase lying between a localized-electron phase and a Fermi-liquid phase; this intermediate phase exhibits quantum-critical-point behaviour with strong electron-lattice interactions making charge transport vibronic. Ordering of the bond-length fluctuations at lower temperatures would normally stabilize a charge-density wave (CDW), which suppresses superconductivity. It is argued that in the copper oxide superconductors, crossover occurs at an optimal doping concentration for the formation of ordered two-electron/two-hole bosonic bags of spin S = 0 in a matrix of localized spins; the correl...

  13. Bond Alternation in Halogen Substituted Polyacetylene ---Possibility of C-F Bond Length Alternation in (CF)x---

    Science.gov (United States)

    Abdelaty, S. M.; Sasai, M.; Fukutome, H.

    1985-08-01

    Using the Hückel model, we study the π electronic and lattice structures of the ground state of halogen substituted polyacetylene (CX)x where X is F, Cl, Br or I. The halogen substitution always makes the C-C bond length alternation in the main chain and the corresponding band gap smaller than those in unsubstituted polyacetylene (CH)x. (CCl)x, (CBr)x and (CI)x have only the bond alternation in the main chain. (CF)x may take one of the three lattice structures depending on the value of the C-F σ bond force constant; the structure with the bond alternation in the main chain, the one with the bond length alternation in the C-F bonds and the one with coexistence of the two kinds of bond alternation. The structure with the C-F bond length alternation is ferroelectric.

  14. Cyanine-like dyes with large bond-length alternation.

    Science.gov (United States)

    Thorley, Karl J; Hales, Joel M; Kim, Hyeongeu; Ohira, Shino; Brédas, Jean-Luc; Perry, Joseph W; Anderson, Harry L

    2013-07-29

    Herein, the synthesis and properties of alkyne-bridged carbocations, which are analogous in structure to cyanine dyes, are reported. An alkene-bridged dye, linked at the third position of the indole, was also synthesized as a reference compound. These new carbocations are stable under ambient conditions, allowing characterization by UV/Vis and NMR ((1)H and (13)C) spectroscopies. These techniques revealed a large degree of delocalization of the positive charge, similar to a previously reported porphyrin carbocation. The linear and nonlinear optical properties are compared with cyanine dyes and triarylmethyl cations, to investigate the effects of the bond-length alternation and the overall molecular geometry. The value of Re(γ), the real part of the third-order microscopic polarizability, of -1.3×10(-33)  esu for the alkyne-linked cation is comparable to that of a cyanine dye of similar length. Nondegenerate two-photon absorption spectra showed that the alkene-bridged dye exhibited characteristics of cyanines, whereas the alkyne-bridged dye is reminiscent of octupolar chromophores, such as the triarylmethyl carbocation brilliant green. Such attributes were confirmed and rationalized by quantum chemical calculations.

  15. Predictions of the bond length and vibrational frequency of Ge/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Northrup, J.E.; Cohen, M.L.

    1983-12-02

    A pseudopotential local spin density calculation of the bond length, vibrational frequency, and binding energy for the ..sigma../sub g//sup -/ state of the germanium dimer is presented. Predictions for the equilibrium bond length and vibrational frequency are given. An overestimate of the binding energy is obtained; this is consistent with other local density calculations for sp bonded diatomic molecules.

  16. Predictions of the bond length and vibrational frequency of Ge 2

    Science.gov (United States)

    Northrup, John E.; Cohen, Marvin L.

    1983-12-01

    We present a pseudopotential local spin density calculation of the bond length, vibrational frequency, and binding energy for the 3Σ g- state of the germanium dimer. Predictions for the equilibrium bond length and vibrational frequency are given. An overestimate of the binding energy is obtained; this is consistent with other local spin density calculations for sp bonded diatomic molecules.

  17. Bond length variation with coverage for caesium adsorption on Si{111} (7 × 7)

    Science.gov (United States)

    Batchelor, D. R.; King, D. A.

    1991-11-01

    The adsorption of Cs on the Si{111} (7 × 7) surface has been studied using SEXAFS. A contraction is observed in the CsSi bond length from 3.79±0.04 Å at low to 3.50±0.04 Å at saturation coverage. At the lower coverage, a longer bond length can be attributed to a degree of ionicity in the CsSi surface bond, due to charge transfer from Cs to the Si. The saturation coverage bond length is consistent with covalent bonding and at this coverage a second site is also populated which has CsSi bond length of 4.68±0.06 Å.

  18. Molecular Adsorption Bond Lengths at Metal Oxide Surfaces: Failure of Current Theoretical Methods

    Energy Technology Data Exchange (ETDEWEB)

    Hoeft, J.-T.; Kittel, M.; Polcik, M.; Bao, S.; Toomes, R. L.; Kang, J.-H.; Woodruff, D. P.; Pascal, M.; Lamont, C. L. A.

    2001-08-20

    New experimental structure determinations for molecular adsorbates on NiO(100) reveal much shorter Ni-C and Ni-N bond lengths for adsorbed CO and NH{sub 3} as well as NO (2.07, 1.88, 2.07{angstrom}) than previously computed theoretical values, with discrepancies up to 0.79{angstrom}, highlighting a major weakness of current theoretical descriptions of oxide-molecule bonding. Comparisons with experimentally determined bond lengths of the same species adsorbed atop Ni on metallic Ni(111) show values on the oxide surface that are consistently larger (0.1--0.3{angstrom}) than on the metal, indicating somewhat weaker bonding.

  19. Bond length, dipole moment, and harmonic frequency of CO

    Science.gov (United States)

    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.

  20. Correlation between carbon-carbon bond length and the ease of retro Diels-Alder reaction

    Indian Academy of Sciences (India)

    Sambasivarao Kotha; Shaibal Banerjee; Mobin Shaikh

    2014-09-01

    The bond length between C8-C9 in (1′R,4′S,4a′R,8a′S)-6′,7′-dimethyl-1′,4′,4a′,8a′-tetrahydrospiro [cyclopropane-1,9′-[1,4]methanonaphthalene]-5′,8′-dione is 1.571 (2) Å and between C7-C12 is 1.567 (2) Å which are longer than the corresponding bond length for saturated bicyclic systems (1.531-1.535Å). This paper reports the correlation between bond length and the ease of retro Diels−Alder reaction.

  1. Bond length alternation and aromaticity in large annulenes

    Science.gov (United States)

    Choi, Cheol Ho; Kertesz, Miklos

    1998-04-01

    Properties of [4n] and [4n+2]annulenes were studied as a function of n for up to [66]annulene using Hartree-Fock and density functional theory in the generalized gradient approximation (DFT-GGA). In the 4n+2 series a "transition" from delocalized to localized structures occurs at 4n+2=30. Various indices of aromaticity, including NMR chemical shifts, bond localization, and aromatic stabilization energy (ASE) were monitored. π-bond localization occurs not due to a dramatic decrease of ASE as n increases, but rather as a result of a pseudo-Jahn-Teller (PJT) effect that sets in as the HOMO-LUMO gap decreases with increasing size. The NMR measures of aromaticity (difference between inner and outer 1H chemical shielding constants and the nucleus-independent chemical shifts, NICS) are reduced in the localized structures in comparison to the delocalized ones. The gradual nature of this "transition" is also implied by the relatively large values of the NMR measures of aromaticity that approach zero only gradually for larger size annulenes. Therefore intermediate size annulenes, such as [30]annulene are predicted to have a localized structure and aromatic properties at the same time showing the delocalized structure is not a necessary condition to be aromatic.

  2. Hydrothermal synthesis of alpha- and beta-HgS nanostructures

    Science.gov (United States)

    Galain, Isabel; María, Pérez Barthaburu; Ivana, Aguiar; Laura, Fornaro

    2017-01-01

    We synthesized HgS nanostructures by the hydrothermal method in order to use them as electron acceptors in hybrid organic-inorganic solar cells. We employed different mercury sources (HgO and Hg(CH3COO)2) and polyvinylpyrrolidone (PVP) or hexadecanethiol (HDT) as stabilizing/capping agent for controlling size, crystallinity, morphology and stability of the obtained nanostructures. We also used thiourea as sulfur source, and a temperature of 180 °C during 6 h. Synthesized nanostructures were characterized by powder X-Ray Diffraction, Diffuse Reflectance Infrared Fourier Transform and Transmission Electron Microscopy. When PVP acts as stabilizing agent, the mercury source has influence on the size -but not in morphology- of the beta-HgS obtained nansostructures. HDT has control over nanostructures' size and depending on the relation Hg:HDT, we obtained a mixture of alpha and beta HgS which can be advantageous in the application in solar cells, due their absorption in different spectral regions. The smallest nanostructures obtained have a mean diameter of 20 nm when using HDT as capping agent. Also, we deposited the aforementioned nanostructures onto flat glass substrates by the spin coating technique as a first approach of an active layer of a solar cell. The depositions were characterized by atomic force microscopy. We obtained smaller particle deposition and higher particle density -but a lower area coverage (5%) - in samples with HDT as capping agent. This work presents promising results on nanostructures for future application on hybrid solar cells. Further efforts will be focused on the deposition of organic-inorganic layers.

  3. Bond length and local energy density property connections for non-transition-metal oxide-bonded interactions.

    Science.gov (United States)

    Gibbs, G V; Spackman, M A; Jayatilaka, D; Rosso, K M; Cox, D F

    2006-11-01

    For a variety of molecules and earth materials, the theoretical local kinetic energy density, G(r(c)), increases and the local potential energy density, V(r(c)), decreases as the M-O bond lengths (M = first- and second-row metal atoms bonded to O) decrease and the electron density, rho(r(c)), accumulates at the bond critical points, r(c). Despite the claim that the local kinetic energy density per electronic charge, G(r(c))/rho(r(c)), classifies bonded interactions as shared interactions when less than unity and closed-shell when greater, the ratio was found to increase from 0.5 to 2.5 au as the local electronic energy density, H(r(c)) = G(r(c)) + V(r(c)), decreases and becomes progressively more negative. The ratio appears to be a measure of the character of a given M-O bonded interaction, the greater the ratio, the larger the value of rho(r(c)), the smaller the coordination number of the M atom and the more shared the bonded interaction. H(r(c))/rho(r(c)) versus G(r(c))/rho(r(c)) scatter diagrams categorize the M-O bonded interactions into domains with the local electronic energy density per electron charge, H(r(c))/rho(r(c)), tending to decrease as the electronegativity differences for the bonded pairs of atoms decrease. The values of G(r(c)) and V(r(c)), estimated with a gradient-corrected electron gas theory expression and the local virial theorem, are in good agreement with theoretical values, particularly for the bonded interactions involving second-row M atoms. The agreement is poorer for shared C-O and N-O bonded interactions.

  4. Relation Between Bond-Length Alternation and Second Electronic Hyperpolarizability of Conjugated Organic Molecules

    Science.gov (United States)

    Marder, Seth R.; Perry, Joseph W.; Bourhill, Grant; Gorman, Christopher B.; Tiemann, Bruce G.; Mansour, Kamjou

    1993-07-01

    The solvent dependence of the second hyperpolarizability, γ, of a variety of unsaturated organic compounds has been measured by third harmonic generation at 1907 nanometers. It is seen that the measured γ is a function of solvent polarity. These solvent-dependent hyperpolarizabilities are associated with changes in molecular geometry from a highly bond-length alternated, polyene-like structure for a formyl-substituted compound in non-polar solvents, to a cyanine-like structure, with little bond-length alternation, for a dicyanovinyl-substituted compound in polar solvents. By tuning bond-length alternation, γ can be optimized in either a positive or negative sense for polymethine dyes of a given conjugation length.

  5. Insights into the enhanced Ce[triple bond, length as m-dash]N triple bond in the HCe[triple bond, length as m-dash]N molecule.

    Science.gov (United States)

    Pu, Zhen; Yu, Wenjie; Roy, Soumendra K; Li, Chaoyang; Ao, Bingyun; Liu, Tianwei; Shuai, Maobing; Wang, Xuefeng

    2017-03-22

    Herein, an experimental study of the vibrational spectra of HCeN was carried out in solid argon, followed by theoretical investigations of molecular structures and the nature of Ce[triple bond, length as m-dash]N bond. The absorption band at 937.7 cm(-1) with the 1.0311 (14)N/(15)N isotopic shift ratio is characteristic of Ce[triple bond, length as m-dash]N stretching band for HCeN, showing a 94 cm(-1) higher shift relative to that of the diatomic CeN molecule. This large frequency shift indicates a much stronger Ce[triple bond, length as m-dash]N bond in HCeN, which is confirmed by DFT calculations. Qualitative orbital interaction and orbital composition analyses suggest that the addition of the H ligand to the Ce center will activate the 4f valence shell and strengthen the covalent bond between Ce and N, which may contribute to enhance the Ce[triple bond, length as m-dash]N triple bond in the HCeN molecule.

  6. Theoretical Electron Density Distributions for Fe- and Cu-Sulfide Earth Materials: A Connection between Bond Length, Bond Critical Point Properties, Local Energy Densities, and Bonded Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, Gerald V.; Cox, David F.; Rosso, Kevin M.; Ross, Nancy L.; Downs, R. T.; Spackman, M. A.

    2007-03-01

    Bond critical point and local energy density properties together with net atomic charges were calculated for theoretical electron density distributions, F(r), generated for a variety of Fe and Cu metal-sulfide materials with high- and low-spin Fe atoms in octahedral coordination and high-spin Fe atoms in tetrahedral coordination. The electron density, F(rc), the Laplacian, 32F(rc), the local kinetic energy, G(rc), and the oxidation state of Fe increase as the local potential energy density, V(rc), the Fe-S bond lengths, and the coordination numbers of the Fe atoms decrease. The properties of the bonded interactions for the octahedrally coordinated low-spin Fe atoms for pyrite and marcasite are distinct from those for high-spin Fe atoms for troilite, smythite, and greigite. The Fe-S bond lengths are shorter and the values of F(rc) and 32F(rc) are larger for pyrite and marcasite, indicating that the accumulation and local concentration of F(r) in the internuclear region are greater than those involving the longer, high-spin Fe-S bonded interactions. The net atomic charges and the bonded radii calculated for the Fe and S atoms in pyrite and marcasite are also smaller than those for sulfides with high-spin octahedrally coordinated Fe atoms. Collectively, the Fe-S interactions are indicated to be intermediate in character with the low-spin Fe-S interactions having greater shared character than the highspin interactions. The bond lengths observed for chalcopyrite together with the calculated bond critical point properties are consistent with the formula Cu+Fe3+S2. The bond length is shorter and the F(rc) value is larger for the FeS4 tetrahedron displayed by metastable greigite than those displayed by chalcopyrite and cubanite, consistent with a proposal that the Fe atom in greigite is tetravalent. S-S bond paths exist between each of the surface S atoms of adjacent slabs of FeS6 octahedra comprising the layer sulfide smythite, suggesting that the neutral Fe3S4 slabs are

  7. Bond length and charge density variations within extended arm chair defects in graphene.

    Science.gov (United States)

    Warner, Jamie H; Lee, Gun-Do; He, Kuang; Robertson, Alex W; Yoon, Euijoon; Kirkland, Angus I

    2013-11-26

    Extended linear arm chair defects are intentionally fabricated in suspended monolayer graphene using controlled focused electron beam irradiation. The atomic structure is accurately determined using aberration-corrected transmission electron microscopy with monochromation of the electron source to achieve ∼80 pm spatial resolution at an accelerating voltage of 80 kV. We show that the introduction of atomic vacancies in graphene disrupts the uniformity of C-C bond lengths immediately surrounding linear arm chair defects in graphene. The measured changes in C-C bond lengths are related to density functional theory (DFT) calculations of charge density variation and corresponding DFT calculated structural models. We show good correlation between the DFT predicted localized charge depletion and structural models with HRTEM measured bond elongation within the carbon tetragon structure of graphene. Further evidence of bond elongation within graphene defects is obtained from imaging a pair of 5-8-5 divacancies.

  8. The effect of substituents on triply bonded boron[triple bond, length as m-dash]antimony molecules: a theoretical approach.

    Science.gov (United States)

    Lu, Jia-Syun; Yang, Ming-Chung; Su, Ming-Der

    2017-03-15

    Three (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP and B3LYP/LANL2DZ+dp) levels of theory are used to study the effect of substituents on the potential energy surfaces of RB[triple bond, length as m-dash]SbR (R = F, OH, H, CH3, SiH3, SiMe(SitBu3)2, SiiPrDis2 and NHC). The theoretical results demonstrate that the triply bonded RB[triple bond, length as m-dash]SbR molecules favor a bent geometry: that is, ∠R-B-Sb ≈ 180° and ∠B-Sb-R ≈ 120°. Regardless of the type of substituents that are attached to the RB[triple bond, length as m-dash]SbR compounds, theoretical evidence strongly indicates that their B[triple bond, length as m-dash]Sb triple bonds have a donor-acceptor nature and are proven to be very weak. Two valence bond models clarify the bonding characters of the B[triple bond, length as m-dash]Sb triple bond. For RB[triple bond, length as m-dash]SbR molecules that feature small substituents, the triple bond is represented as . For RB[triple bond, length as m-dash]SbR molecules that feature large substituents, the triple bond is represented as . Most importantly, this theoretical study predicts that only bulkier substituents significantly stabilize the triply bonded RB[triple bond, length as m-dash]SbR molecules, from the kinetic viewpoint.

  9. Bond length variation in Ga1-xInxAs crystals from the Tersoff potential

    Science.gov (United States)

    Titantah, J. T.; Lamoen, D.; Schowalter, M.; Rosenauer, A.

    2007-06-01

    In this work we show that a reparametrized Tersoff potential accurately reproduces the bond length variations observed in ternary Ga1-xInxAs mixed crystals. The reparametrization is based on accurate first-principles electronic structure calculations. Previous parametrizations of the Tersoff potential for GaAs and InAs structures, although they accurately reproduce the properties of the zinc-blende GaAs and InAs crystals, are shown to be unable to reproduce the bond length variations in these mixed crystals. In addition to correcting the bond length inconsistencies, the new set of parameters is also shown to yield the elastic constants of GaAs and InAs that agree fairly well with measurements and to reproduce accurately their respective melting temperature.

  10. Quantification of hyperconjugative effect on the proton donor X-H bond length changes in the red- and blueshifted hydrogen-bonded complexes

    Science.gov (United States)

    Zhou, Pan-Pan; Qiu, Wen-Yuan; Jin, Neng-Zhi

    2012-08-01

    A whole dataset containing 55 hydrogen bonds were studied at the MP2/aug-cc-pVTZ level of theory. The changes of geometries and stretching vibrational frequencies show that there are 31 redshifted and 24 blueshifted hydrogen-bonded complexes. Natural bond orbital analysis was carried out at the B3LYP/aug-cc-pVTZ level of theory to obtain the electron densities in the bonding and antibonding orbitals of the proton donor X-H bond, which are closely associated with its bond length. Based on their relationship, a generally applicable method considering both the electron densities in the bonding and antibonding orbitals of the proton donor X-H bond has been developed to quantitatively describe the hyperconjugative effect on the X-H bond length changes in these hydrogen-bonded complexes.

  11. Intramolecular bond length dependence of the anisotropic dispersion coefficients for H2-rare gas interactions

    Science.gov (United States)

    Wormer, Paul E. S.; Hettema, Hinne; Thakkar, Ajit J.

    1993-05-01

    Effective states arising from variational perturbation calculations in a full configuration interaction basis are used to calculate dynamic multipole polarizabilities for H2 at seven different bond lengths. These are combined with previously calculated dynamic polarizabilities for rare gas atoms to obtain the intramolecular bond length dependence of the anisotropic C6, C8, and C10 dispersion coefficients for H2-X (X=He, Ne, Ar, Kr, Xe) interactions. The results are generally in good agreement with previous semiempirical estimates where available.

  12. Localized and extended states in doped polyaniline: The effect of bond-length alternation

    Science.gov (United States)

    Dücker, H.; Struck, M.; Koslowski, Th.; von Niessen, W.

    1992-11-01

    We present numerical studies of localization properties of oxidized and protonated disordered polyaniline. The calculations are performed on the single electron level, using Hückel theory for π electrons. The spatial extension of the eigenstates at the Fermi energy is determined by a fast and accurate transfer-matrix scheme. The spatial extension of eigenstates diverges for a large degree of protonation, provided all bonds within the benzoid and quinoid can be described with the same set of tight-binding parameters. Localization effects become important for small degrees of protonation and in systems that show bond-length alternation in quinoid rings and aromatic bonds in benzoid rings.

  13. Isotopic fractionation in proteins as a measure of hydrogen bond length

    Energy Technology Data Exchange (ETDEWEB)

    McKenzie, Ross H., E-mail: r.mckenzie@uq.edu.au [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia); Athokpam, Bijyalaxmi; Ramesh, Sai G. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)

    2015-07-28

    If a deuterated molecule containing strong intramolecular hydrogen bonds is placed in a hydrogenated solvent, it may preferentially exchange deuterium for hydrogen. This preference is due to the difference between the vibrational zero-point energy for hydrogen and deuterium. It is found that the associated fractionation factor Φ is correlated with the strength of the intramolecular hydrogen bonds. This correlation has been used to determine the length of the H-bonds (donor-acceptor separation) in a diverse range of enzymes and has been argued to support the existence of short low-barrier H-bonds. Starting with a potential energy surface based on a simple diabatic state model for H-bonds, we calculate Φ as a function of the proton donor-acceptor distance R. For numerical results, we use a parameterization of the model for symmetric O–H⋯O bonds [R. H. McKenzie, Chem. Phys. Lett. 535, 196 (2012)]. We consider the relative contributions of the O–H stretch vibration, O–H bend vibrations (both in plane and out of plane), tunneling splitting effects at finite temperature, and the secondary geometric isotope effect. We compare our total Φ as a function of R with NMR experimental results for enzymes, and in particular with an earlier model parametrization Φ(R), used previously to determine bond lengths.

  14. Bond length-bond angle correlation in densified silica—Results from 17O NMR spectroscopy

    Science.gov (United States)

    Trease, Nicole M.; Clark, Ted M.; Grandinetti, Philip J.; Stebbins, Jonathan F.; Sen, Sabyasachi

    2017-05-01

    Pressure induced correlated evolution of the distributions of the Si-O distance and Si-O-Si inter-tetrahedral bond angle in vitreous silica quenched from pressures of up to ˜14 GPa at ambient temperature is measured in unprecedented detail using two-dimensional dynamic-angle-spinning 17O nuclear magnetic resonance spectroscopy. The results demonstrate that, in contrast to the conventional wisdom, vitreous silica undergoes irreversible structural changes even at pressures as low as ˜8 GPa. These structural changes at the short range involve a progressive reduction in the mean Si-O-Si angle and a broadening of the corresponding distribution, with increasing pressure. This bond angle reduction is accompanied by a concomitant monotonic increase in the mean Si-O distance. The mean values of the Si-O-Si angle and Si-O distance at various pressures closely follow the minimum in the corresponding potential energy surface calculated for the H6Si2O7 dimer molecule.

  15. Local density approximation results for bond length alternation in the infinite polyyne chain

    Science.gov (United States)

    Bylaska, Eric; Weare, John

    1998-03-01

    Calculations for large even numbered carbon ring molecules and band structure calculations for the infinite polyyne chain within the local density approximation are reported. We studied the alternation of bond lengths in this system as a function of size. Particular focus is on alternation in the infinite system. For intermediate and large sized Cn rings with n satisfying n=4N (doubly-antiaromatic rings) there is a substantial first order Jahn-Teller distortion which decreases for large N. On the other hand, for Cn rings satisfying n=4N+2 (doubly-aromatic rings) the second order Jahn-Teller distortion does not produce bond length alternation even by the large C_42 ring. The persistance of aromatic behavior in the very large carbon rings manifests itself in the band structure calculations by making the amount of bond length alternation predicted for the infinite polyyne chain extremely sensitive to the numerical treatment of the Brillouin zone. We have shown that the infinite polyyne has a finite amount of bond length alternation but the condensation energy is very small.

  16. Applications of the Local Mode Model to CH Bond Length Changes, Molecular Conformations and Vibrational Dynamics

    OpenAIRE

    Henry, Bryan R.; Gough, Kathleen M.

    1983-01-01

    The theoretical basis for the local mode model is reviewed. The model is applied to gas phase overtone spectra of aromatic molecules to investigate both substituent induced CH bond length changes and conformationally inequivalent hydrogens. The dynamic implications of the local mode model are discussed.

  17. Effect of bond length and radius on superconducting transition temperature for FeAs-based superconductors

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    By comparing the data of lattice parameters of more than 50 new FeAs-based high temperature superconductors in two syetems, the effect of bondlength on superconducting transition temperature (T C ) was found that, for both FeAs superconductor systems with similar ionic radii of cation A, the bond length L As-A between Arsenic atom and its nearest neighbor cation at the A site is in an inverse proportion to T C , i.e. the larger the bond length L As-A , the lower the T C . In addition, we also found a noticeable effect of ionic radius on T C , in which deviation from the tendency line of bond length vs. T C decreases with the increasing ionic radius. Both bond length-T C and ionic radii-T C relations indicate that the interaction of cation A and As ion have significant effect on superconductivity. The analysis on the electronic structure indicates that there exists the proximity of the secondary-outer p-orbit of the cation A and the 4s orbit of the As ion, both in energy space and in real space. Some high frequency individual vibrating modes would be established through exchange coupling on their inner orbits. It is worth of mention that the superconducting condensation is influenced by the interaction between the cation A and the As atoms.

  18. Complex transition metal hydrides: linear correlation of countercation electronegativity versus T-D bond lengths.

    Science.gov (United States)

    Humphries, T D; Sheppard, D A; Buckley, C E

    2015-06-30

    For homoleptic 18-electron complex hydrides, an inverse linear correlation has been established between the T-deuterium bond length (T = Fe, Co, Ni) and the average electronegativity of the metal countercations. This relationship can be further employed towards aiding structural solutions and predicting physical properties of novel complex transition metal hydrides.

  19. Variation of persistence length with concentration in a hydrogen bonding polymer solution

    Science.gov (United States)

    Sukumaran, S.; Beaucage, G.

    2000-03-01

    Miscibility of some polymers in water is usually attributed to the ability of the polymer to hydrogen bond with water. Hydrogen bonding contributes a strong interaction component to the free energy that enhances mixing between the polymer and water. It is widely known that certain conformations of the polymer have significantly higher dipole moment and consequently higher affinity for water. If the solvent alters the bond rotation energetics of the polymer it is natural to expect the average local structure of the chain to be affected leading to a change in the persistence length. Small angle neutron scattering experiments were performed on aqueous (D2O) solutions of a polymer (PEO or PVME) at different concentrations to investigate the microscopic structure of these solutions. The persistence length was strongly dependent on concentration. A simple physical explanation for this phenomenon will be provided. Possible ramifications of such a phenomenon in understanding phase behavior will be indicated.

  20. Calculation of Bond-length, Bond-energy and Force Constant of Hydrogen Molecule by Classical Mechanics

    Institute of Scientific and Technical Information of China (English)

    ChenJing

    2004-01-01

    Until recently the hydrogen molecule structural parameters are calculated with the methods of quantum mechanics. To achieve results close to experimental values, the wave function used is complicated and has no clear physical meaning. Because the distribution of the electron probability density is a statistical rule, the macro-time has actually been used in the concept on a electron cloud graph. Here are obtained three formulas with a classical mechanics method on the bond-length re , bond-energy De and force constant k of the ground state hydrogen molecule, which have a clear physical meaning but no artificial parameters, and compared with experimental values, the relative errors are respectively less than 1% , 2% and 4% .

  1. Scaling of the critical free length for progressive unfolding of self-bonded graphene

    Energy Technology Data Exchange (ETDEWEB)

    Kwan, Kenny; Cranford, Steven W., E-mail: s.cranford@neu.edu [Laboratory of Nanotechnology in Civil Engineering (NICE), Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, Massachusetts 02115 (United States)

    2014-05-19

    Like filled pasta, rolled or folded graphene can form a large nanocapsule surrounding a hollow interior. Use as a molecular carrier, however, requires understanding of the opening of such vessels. Here, we investigate a monolayer sheet of graphene as a theoretical trial platform for such a nanocapsule. The graphene is bonded to itself via aligned disulfide (S-S) bonds. Through theoretical analysis and atomistic modeling, we probe the critical nonbonded length (free length, L{sub crit}) that induces fracture-like progressive unfolding as a function of folding radius (R{sub i}). We show a clear linear scaling relationship between the length and radius, which can be used to determine the necessary bond density to predict mechanical opening/closing. However, stochastic dissipated energy limits any exact elastic formulation, and the required energy far exceeds the dissociation energy of the S-S bond. We account for the necessary dissipated kinetic energy through a simple scaling factor (Ω), which agrees well with computational results.

  2. Indirect versus direct photoionization with ultrashort pulses: interferences and time-resolved bond-length changes

    Science.gov (United States)

    Gräfe, S.; Engel, V.

    2004-02-01

    The photoionization of NaI molecules with femtosecond laser pulses leads to photoelectron distributions which vary with the delay between a pump- and a probe-pulse. If the vibrational wave packet as prepared in the pump-transition is located in a region where the bonding character is ionic, the photoelectron, due to its localization on the iodine atom, may be ejected directly or be scattered from the Na + ion. This leads to structures in the photoelectron spectrum which, in turn, reflect temporal bond-length changes.

  3. Anatomy of bond formation. Bond length dependence of the extent of electron sharing in chemical bonds from the analysis of domain-averaged Fermi holes.

    Science.gov (United States)

    Ponec, Robert; Cooper, David L

    2007-01-01

    We demonstrate that domain-average Fermi hole (DAFH) analysis, which has previously been used at the Hartree-Fock level, remains useful after the proper introduction of electron correlation. We perform a systematic investigation of the variation of the picture of bonding with increasing bond length in simple diatomic molecules such as N2 and LiH. Alongside values of a shared-electron distribution index (SEDI), this analysis provides further insight into the geometry dependence of the extent of electron sharing in polar and non-polar systems. We also use DAFH analysis, with correlated wave functions, to evaluate the (potential) multicentre bonding in the electron-deficient and electron-rich molecules CH2Li2 and CH2N2, respectively.

  4. Isotopic fractionation in proteins as a measure of hydrogen bond length

    CERN Document Server

    McKenzie, Ross H; Ramesh, Sai

    2015-01-01

    If a deuterated molecule containing strong intramolecular hydrogen bonds is placed in a hydrogenated solvent it may preferentially exchange deuterium for hydrogen. This preference is due to the difference between the vibrational zero-point energy for hydrogen and deuterium. It is found that the associated fractionation factor $\\Phi$ is correlated with the strength of the intramolecular hydrogen bonds. This correlation has been used to determine the length of the H-bonds (donor-acceptor separation) in a diverse range of enzymes and has been argued to support the existence of short low-barrier H-bonds. Starting with a potential energy surface based on a simple diabatic state model for H-bonds we calculate $\\Phi$ as a function of the proton donor-acceptor distance $R$. For numerical results, we use a parameterization of the model for symmetric O-H.... O bonds. We consider the relative contributions of the O-H stretch vibration, O-H bend vibrations (both in plane and out of plane), tunnelling splitting effects at...

  5. The effect of substituents on the stability of triply bonded gallium[triple bond, length as m-dash]antimony molecules: a new target for synthesis.

    Science.gov (United States)

    Lu, Jia-Syun; Yang, Ming-Chung; Su, Ming-Der

    2017-02-14

    The effect of substitution on the potential energy surfaces of RGa(-)[triple bond, length as m-dash]Sb(+)R (R = F, OH, H, CH3, SiH3, SiMe(SitBu3)2, SiiPrDis2 and NHC) is studied using density functional theory (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP and B3LYP/LANL2DZ + dp). The computational results show that all of the triply bonded RGa(-)[triple bond, length as m-dash]Sb(+)R molecules have a preference for a bent geometry (i.e., ∠RGaSb ≈ 180° and ∠GaSbR ≈ 90°), which can be described using a valence bond model. The theoretical results show that because RGa(-)[triple bond, length as m-dash]Sb(+)R has smaller electropositive groups, it could be both kinetically and thermodynamically stable and may be experimentally detectable. However, these theoretical results predict that the triply bonded R'Ga(-)[triple bond, length as m-dash]Sb(+)R' molecules that have bulkier groups (R' = SiMe(SitBu3)2, SiiPrDis2, and NHC) are kinetically stable. In other words, both the electronic and the steric effects of bulkier substituent groups mean that it should be possible to experimentally isolate triply bonded RGa(-)[triple bond, length as m-dash]Sb(+)R molecules in a stable form.

  6. Comparison of theoretical approaches for computing the bond length alternation of polymethineimine

    Energy Technology Data Exchange (ETDEWEB)

    Jacquemin, Denis [Laboratoire de Chimie Theorique Appliquee, Facultes Universitaires Notre-Dame de la Paix, rue de Bruxelles, 61, B-5000 Namur (Belgium)], E-mail: denis.jacquemin@fundp.ac.be; Perpete, Eric A. [Laboratoire de Chimie Theorique Appliquee, Facultes Universitaires Notre-Dame de la Paix, rue de Bruxelles, 61, B-5000 Namur (Belgium); Chermette, Henry [Laboratoire de Chimie Physique Theorique, Universite Claude Bernard, Lyon I Bat. 210, and CNRS UMR 5180 43, Boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France); Ciofini, Ilaria; Adamo, Carlo [Ecole Nationale Superieure de Chimie de Paris, Laboratoire Electrochimie et Chimie Analytique, UMR CNRS ENSCP no. 7575, rue Pierre et Marie Curie, 11 F-75321 Paris Cedex 05 (France)

    2007-01-25

    Using electron-correlated wavefunction approaches and several pure and hybrid density functionals combined with three atomic basis sets, we have optimized the ground-state geometry of increasingly long polymethineimine oligomers presenting all-trans and gliding-plane symmetries. It turns out that MP2 bond length alternations (BLA) are in good agreement with higher-order electron-correlated wavefunction approaches, whereas, for both conformers, large qualitative and quantitative discrepancies between MP2 and DFT geometries have been found. Indeed, all the selected GGA, meta-GGA and hybrid functionals tend to overestimate bond length equalization in extended polymethineimine structures. On the other hand, self-interaction corrections included in the ADSIC framework provide, in this particular case, a more efficient approach to predict the BLA for medium-size oligomers.

  7. Mathematical Simulation of Graphene With Modified c-c Bond Length and Transfer Energy

    Directory of Open Access Journals (Sweden)

    P.A. Alvi

    2011-01-01

    Full Text Available In nanotechnology research, allotropes of carbon like Graphene, Fullerene (Buckyball and Carbon nanotubes are widely used due to their remarkable properties. Electrical and mechanical properties of those allotropes vary with their molecular geometry. This paper is specially based on modeling and simulation of graphene in order to calculate energy band structure in k space with varying the C-C bond length and C-C transfer energy. Significant changes have been observed in the energy band structure of graphene due to variation in C-C bond length and C-C transfer energy. In particular, this paper focuses over the electronic structure of graphene within the frame work of tight binding approximation. It has been reported that conduction and valence states in graphene only meet at two points in k-space and that dispersion around these special points is conical.

  8. Comparison of theoretical approaches for computing the bond length alternation of polymethineimine

    Science.gov (United States)

    Jacquemin, Denis; Perpète, Eric A.; Chermette, Henry; Ciofini, Ilaria; Adamo, Carlo

    2007-01-01

    Using electron-correlated wavefunction approaches and several pure and hybrid density functionals combined with three atomic basis sets, we have optimized the ground-state geometry of increasingly long polymethineimine oligomers presenting all- trans and gliding-plane symmetries. It turns out that MP2 bond length alternations (BLA) are in good agreement with higher-order electron-correlated wavefunction approaches, whereas, for both conformers, large qualitative and quantitative discrepancies between MP2 and DFT geometries have been found. Indeed, all the selected GGA, meta-GGA and hybrid functionals tend to overestimate bond length equalization in extended polymethineimine structures. On the other hand, self-interaction corrections included in the ADSIC framework provide, in this particular case, a more efficient approach to predict the BLA for medium-size oligomers.

  9. Primary Role of the Chromophore Bond Length Alternation in Reversible Photoconversion of Red Fluorescence Proteins

    Science.gov (United States)

    Drobizhev, Mikhail; Hughes, Thomas E.; Stepanenko, Yuriy; Wnuk, Pawel; O'Donnell, Kieran; Scott, J. Nathan; Callis, Patrik R.; Mikhaylov, Alexander; Dokken, Leslie; Rebane, Aleksander

    2012-01-01

    Rapid photobleaching of fluorescent proteins can limit their use in imaging applications. The underlying kinetics is multi-exponential and strongly depends on the local chromophore environment. The first, reversible, step may be attributed to a rotation around one of the two exocyclic C-C bonds bridging phenol and imidazolinone groups in the chromophore. However it is not clear how the protein environment controls this motion - either by steric hindrances or by modulating the electronic structure of the chromophore through electrostatic interactions. Here we study the first step of the photobleaching kinetics in 13 red fluorescent proteins (RFPs) with different chromophore environment and show that the associated rate strongly correlates with the bond length alternation (BLA) of the two bridge bonds. The sign of the BLA appears to determine which rotation is activated. Our results present experimental evidence for the dominance of electronic effects in the conformational dynamics of the RFP chromophore. PMID:23008753

  10. Primary Role of the Chromophore Bond Length Alternation in Reversible Photoconversion of Red Fluorescence Proteins

    Science.gov (United States)

    Drobizhev, Mikhail; Hughes, Thomas E.; Stepanenko, Yuriy; Wnuk, Pawel; O'Donnell, Kieran; Scott, J. Nathan; Callis, Patrik R.; Mikhaylov, Alexander; Dokken, Leslie; Rebane, Aleksander

    2012-09-01

    Rapid photobleaching of fluorescent proteins can limit their use in imaging applications. The underlying kinetics is multi-exponential and strongly depends on the local chromophore environment. The first, reversible, step may be attributed to a rotation around one of the two exocyclic C-C bonds bridging phenol and imidazolinone groups in the chromophore. However it is not clear how the protein environment controls this motion - either by steric hindrances or by modulating the electronic structure of the chromophore through electrostatic interactions. Here we study the first step of the photobleaching kinetics in 13 red fluorescent proteins (RFPs) with different chromophore environment and show that the associated rate strongly correlates with the bond length alternation (BLA) of the two bridge bonds. The sign of the BLA appears to determine which rotation is activated. Our results present experimental evidence for the dominance of electronic effects in the conformational dynamics of the RFP chromophore.

  11. Bond-length-alternation and the hyperpolarizabilities of a charged soliton in polyenic chains

    Science.gov (United States)

    An, Z.; Wong, K. Y.

    2003-07-01

    Nonlinear optical responses of a charged soliton were studied using a model charged polyenic chain. It was found that simple derivative relations exist between the spatial profile of the bond-length-alternation and the profiles of the real-space description of the linear polarizability and the first and second hyperpolarizabilities of the chain. These relations can be understood if the soliton is assumed to undergo a sliding translational motion under the influence of an external electric field.

  12. Mathematical Simulation of Graphene With Modified c-c Bond Length and Transfer Energy

    OpenAIRE

    P.A. Alvi; S.Z. Hashmi; S. Dalela; Rahman, F.

    2011-01-01

    In nanotechnology research, allotropes of carbon like Graphene, Fullerene (Buckyball) and Carbon nanotubes are widely used due to their remarkable properties. Electrical and mechanical properties of those allotropes vary with their molecular geometry. This paper is specially based on modeling and simulation of graphene in order to calculate energy band structure in k space with varying the C-C bond length and C-C transfer energy. Significant changes have been observed in the energy band struc...

  13. Is it True That the Normal Valence-Length Correlation Is Irrelevant for Metal-Metal Bonds?

    Science.gov (United States)

    Singh, Vijay; Dixit, Mudit; Kosa, Monica; Major, Dan Thomas; Levi, Elena; Aurbach, Doron

    2016-04-04

    The most intriguing feature of metal-metal bonds in inorganic compounds is an apparent lack of correlation between the bond order and the bond length. In this study, we combine a variety of literature data obtained by quantum chemistry and our results based on the empirical bond valence model (BVM), to confirm for the first time the existence of a normal exponential correlation between the effective bond order (EBO) and the length of the metal-metal bonds. The difference between the EBO and the formal bond order is attributed to steric conflict between the (TM)n cluster (TM=transition metal) and its environment. This conflict, affected mainly by structural type, should cause high lattice strains, but electron redistribution around TM atoms, evident from the BVM calculations, results in a full or partial strain relaxation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. An investigation of the interrelationships between linear and nonlinear polarizabilities and bond-length alternation in conjugated organic molecules.

    Science.gov (United States)

    Gorman, C B; Marder, S R

    1993-01-01

    A computational method was devised to explore the relationship of charge separation, geometry, molecular dipole moment (mu), polarizability (alpha), and hyperpolariz-abilities (beta, gamma) in conjugated organic molecules. We show that bond-length alternation (the average difference in length between single and double bonds in the molecule) is a key structurally observable parameter that can be correlated with hyperpolarizabilities and is thus relevant to the optimization of molecules and materials. By using this method, the relationship of bond-length alternation, mu, alpha, beta, and gamma for linear conjugated molecules is illustrated, and those molecules with maximized alpha, beta, and gamma are described. PMID:11607441

  15. An Investigation of the Interrelationships Between Linear and Nonlinear Polarizabilities and Bond-Length Alternation in Conjugated Organic Molecules

    Science.gov (United States)

    Gorman, Christopher B.; Marder, Seth R.

    1993-12-01

    A computational method was devised to explore the relationship of charge separation, geometry, molecular dipole moment (μ), polarizability (α), and hyperpolariz-abilities (β, γ) in conjugated organic molecules. We show that bond-length alternation (the average difference in length between single and double bonds in the molecule) is a key structurally observable parameter that can be correlated with hyperpolarizabilities and is thus relevant to the optimization of molecules and materials. By using this method, the relationship of bond-length alternation, μ, α, β, and γ for linear conjugated molecules is illustrated, and those molecules with maximized α, β, and γ are described.

  16. A new class of cyanine-like dyes with large bond-length alternation.

    Science.gov (United States)

    Ohira, Shino; Hales, Joel M; Thorley, Karl J; Anderson, Harry L; Perry, Joseph W; Brédas, Jean-Luc

    2009-05-06

    Cyanines, which represent a class of charged chromophores with an odd number of pi-conjugated carbons, display unique electronic and optical properties attributed to the strong electronic delocalization and the absence of any significant carbon-carbon bond-length alternation (BLA) along their backbones. The flatness of the corresponding electronic potential makes cyanine dyes the compounds to which simple free-electron theory can be applied in the most relevant way. Recently, cations of porphyrin dimers linked by a pi-conjugated bridge with an odd number of carbons and presenting alternating single and triple bonds were shown to possess linear and nonlinear optical properties analogous to those of cyanines. Here, by using a joint theoretical and experimental approach, we demonstrate the correspondence between cyanines and the new class of alkyne carbocations, in spite of their marked difference in BLA.

  17. Comparative study on direct and indirect bracket bonding techniques regarding time length and bracket detachment

    Directory of Open Access Journals (Sweden)

    Jefferson Vinicius Bozelli

    2013-12-01

    Full Text Available OBJECTIVE: The aim of this study was to assess the time spent for direct (DBB - direct bracket bonding and indirect (IBB - indirect bracket bonding bracket bonding techniques. The time length of laboratorial (IBB and clinical steps (DBB and IBB as well as the prevalence of loose bracket after a 24-week follow-up were evaluated. METHODS: Seventeen patients (7 men and 10 women with a mean age of 21 years, requiring orthodontic treatment were selected for this study. A total of 304 brackets were used (151 DBB and 153 IBB. The same bracket type and bonding material were used in both groups. Data were submitted to statistical analysis by Wilcoxon non-parametric test at 5% level of significance. RESULTS: Considering the total time length, the IBB technique was more time-consuming than the DBB (p < 0.001. However, considering only the clinical phase, the IBB took less time than the DBB (p < 0.001. There was no significant difference (p = 0.910 for the time spent during laboratorial positioning of the brackets and clinical session for IBB in comparison to the clinical procedure for DBB. Additionally, no difference was found as for the prevalence of loose bracket between both groups. CONCLUSION: the IBB can be suggested as a valid clinical procedure since the clinical session was faster and the total time spent for laboratorial positioning of the brackets and clinical procedure was similar to that of DBB. In addition, both approaches resulted in similar frequency of loose bracket.

  18. Relationship between band gap and bond length alternation in organic conjugated polymers

    Science.gov (United States)

    Bredas, J. L.

    1985-04-01

    A description is given of calculations of the evolution of the band gap as a function of geometry in conjugated polymers based on aromatic rings; polyparaphenylene, polypyrrole, polythiophene. The results demonstrate that the gap decreases as a function of increasing quinoid character of the backbone and is thus not minimal in the case of zero bond length alternation, in contrast to the situation found in polyacetylene-like compounds. The consequences of these results are stressed for the understanding of the effects of doping and for the design of new organic polymers with small gaps.

  19. On the relationship between bond-length alternation and many-electron self-interaction error

    Science.gov (United States)

    Körzdörfer, Thomas; Parrish, Robert M.; Sears, John S.; Sherrill, C. David; Brédas, Jean-Luc

    2012-09-01

    Predicting accurate bond-length alternations (BLAs) in long conjugated molecular chains has been a major challenge for electronic-structure theory for many decades. While Hartree-Fock (HF) overestimates BLA significantly, second-order perturbation theory and commonly used density functional theory (DFT) approaches typically underestimate it. Here, we discuss how this failure is related to the many-electron self-interaction error (MSIE), which is inherent to both HF and DFT approaches. We use tuned long-range corrected hybrids to minimize the MSIE for a series of polyenes. The key result is that the minimization of the MSIE alone does not yield accurate BLAs. On the other hand, if the range-separation parameter is tuned to yield accurate BLAs, we obtain a significant MSIE that grows with chain length. Our findings demonstrate that reducing the MSIE is one but not the only important aspect necessary to obtain accurate BLAs from density functional theory.

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

    Science.gov (United States)

    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

  1. Synthesis and characterization of the dimercury(I)-linked compound [PPn]4[(Re7C(CO)21Hg)2]. Oxidative cleavage of the mercury-mercury bond leading to carbidoheptarhenate complexes of mercury(II), including [PPN][Re7C(CO)21Hg(S=C(NME2)2)].

    Science.gov (United States)

    Wright, C A; Brand, U; Shapley, J R

    2001-09-10

    The reaction of [PPN](3)[Re(7)C(CO)(21)] with Hg(2)(NO(3))(2).2H(2)O in dichloromethane formed the complex [PPN](4)[(Re(7)C(CO)(21)Hg)(2)] ([PPN](4)[1]), isolated in 60% yield. Analogous salts of [1](4-) with [PPh(4)](+) and [NEt(4)](+) were also prepared. The crystal structure of [PPN](4)[1] showed that two carbidoheptarhenate cores are linked by a dimercury(I) unit (d(Hg-Hg) = 2.610(4) A), with each individual mercury atom face-bridging. Oxidative cleavage of the Hg-Hg bond in [1](4-) was effected by 4-bromophenyl disulfide to form [Re(7)C(CO)(21)HgSC(6)H(4)Br](2-) ([4](2-)), by I(2) to form [Re(7)C(CO)(21)HgI](2-) ([5](2-)), and by Br(2) to form [Re(7)C(CO)(21)HgBr](2-) ([6](2-)). Oxidation of [1](4-) by ferrocenium ion (2 equiv) in the presence of tetramethylthiourea resulted in the derivative [Re(7)C(CO)(21)HgSC(NMe(2))(2)](-) ([7](-)). The molecular structure of [PPN][7] was determined by X-ray crystallography. This is the first example of a carbidoheptarhenate-mercury complex with a neutral ligand on mercury, and ligand exchange was demonstrated by displacement with triethylphosphine. Complex [7](-) can also be prepared by protonating [Re(7)C(CO)(21)HgO(2)CCH(3)](2-) in the presence of tetramethylthiourea. Cyclic voltammetry data to calibrate and compare the redox properties of compounds [1](4-) and [7](-) have been measured.

  2. Geometry and bond-length alternation in nonlinear optical materials. I. Standard parameters in two precursors.

    Science.gov (United States)

    Gainsford, Graeme J; Bhuiyan, M Delower H; Kay, Andrew J

    2007-11-01

    2-{3-Cyano-4-[4-(N-formylanilino)-trans-1,3-butadienyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}propanedinitrile, C(22)H(18)N(4)O(2), (I), and 2-{3-cyano-4-[6-(N-formylanilino)-trans,trans-1,3,5-hexatrienyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}propanedinitrile, C(24)H(20)N(4)O(2), (II), show the alternating single/double-bond behaviour of push-pull chromophores. In the two structures, the planar polyene chains are twisted with respect to the furanylidene ring by 18.2 (2) and 12.4 (2) degrees , respectively. Comparison with structures of related and parent molecules shows subtle but consistent bond-length variations consistent with charge-delocalized structures. Crystal cohesion is provided by various sets of hydrogen bonds, viz. C-H(methyl)...N(cyano) and bifurcated (C=C-H)(2)...O=C in (I), and C-H(methyl/phenyl)...O and C=C-H...N(cyano) in (II).

  3. Bond length and adsorbate vibrations of (2×3)N/Cu(110): A SEXAFS study

    Science.gov (United States)

    Wende, H.; Arvanitis, D.; Tischer, M.; Chauvistré, R.; Henneken, H.; May, F.; Baberschke, K.

    1996-08-01

    Temperature- and angle-dependent surface-extended x-ray-absorption fine-structure (SEXAFS) measurements on the system (2×3)N/Cu(110) are reported. Three inequivalent adsorption sites of the N atoms within the surface unit cell are identified. The successful separation of their contributions in the present SEXAFS analysis allows for a determination of N-Cu bond lengths not only within the surface plane but also to the second Cu layer. The temperature-dependent measurements between 60 and 300 K enable us to separate structural from dynamic effects in the SEXAFS amplitude, leading to a reliable determination of coordination numbers. A strong anisotropy is found in the adsorbate vibrations parallel versus perpendicular to the surface. The relative motion of the N atom relative to the first three Cu neighbor shells is characterized by means of the corresponding Einstein temperatures. These indicate that the N atom is primarily bonded only to four Cu atoms, and not to five as previously suggested. Anharmonic corrections are found necessary for a reliable distance determination of the N-Cu bonds to the second layer. The structural parameters are compared to the ones predicted by the pseudo-(100)-c(2×2)-N reconstruction.

  4. Many-particle effects in the bond length alternation of alternant hydrocarbons

    Science.gov (United States)

    Böhm, Michael C.; Schütt, Johannes

    The local approach (LA) method has been employed to investigate the correlated ground state wavefunction in alternant monocyclic and linear hydrocarbon π systems as a function of the bond length alternation δ. The LA has been supplemented by a simple model-Hamiltonian developed in the ZDO (zero differential overlap) approximation. The integrals have been calculated ab initio in a Slater-type basis. To quantify many-particle effects in the studied systems we have determined the interatomic π correlation energy Ecorr and a π electron localization parameter Δi as a function of δ. Δi measures the reduction of the charge fluctuations due to electronic correlations and is thus a convenient measure for the atomic electron density localization. It is demonstrated that monocyclic 4n + 2 (n = 1,2,3, …) Hückel rings allow for a coincidence of increasing |Ecorr| numbers and increasing atomic electron density delocalization with enlarged δ values. The δ variation of Δi reflects in a transparent form that hydrocarbon π networks are generally distortive. For smaller 4n annulenes and polyenes we find a mutual exclusion between increasing atomic electron density delocalization and enhanced |Ecorr| numbers. Bond alternation enhances here the π delocalization, but reduces the |Ecorr| values. It is suggested that a traditional picture in chemistry should be corrected. Bond length alternation in conjugated π systems is not equivalent with an enhancement of the atomic electron density localization; the opposite is true. In this description 'electronic delocalization' is understood as a dynamic property which is not related to the static charge density, but to the mean square deviation of the electron charge around the respective mean value.

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

    Science.gov (United States)

    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.

  6. Predicted bond length variation in wurtzite and zinc-blende InGaN and AlGaN alloys

    Science.gov (United States)

    Mattila, T.; Zunger, Alex

    1999-01-01

    Valence force field simulations utilizing large supercells are used to investigate the bond lengths in wurtzite and zinc-blende InxGa1-xN and AlxGa1-xN random alloys. We find that (i) while the first-neighbor cation-anion shell is split into two distinct values in both wurtzite and zinc-blende alloys (RGa-N1≠RIn-N1), the second-neighbor cation-anion bonds are equal (RGa-N2=RIn-N2). (ii) The second-neighbor cation-anion bonds exhibit a crucial difference between wurtzite and zinc-blende binary structures: in wurtzite we find two bond distances which differ in length by 13% while in the zinc-blende structure there is only one bond length. This splitting is preserved in the alloy, and acts as a fingerprint, distinguishing the wurtzite from the zinc-blende structure. (iii) The small splitting of the first-neighbor cation-anion bonds in the wurtzite structure due to nonideal c/a ratio is preserved in the alloy, but is obscured by the bond length broadening. (iv) The cation-cation bond lengths exhibit three distinct values in the alloy (Ga-Ga, Ga-In, and In-In), while the anion-anion bonds are split into two values corresponding to N-Ga-N and N-In-N. (v) The cation-related splitting of the bonds and alloy broadening are considerably larger in InGaN alloy than in AlGaN alloy due to larger mismatch between the binary compounds. (vi) The calculated first-neighbor cation-anion and cation-cation bond lengths in InxGa1-xN alloy are in good agreement with the available experimental data. The remaining bond lengths are provided as predictions. In particular, the predicted splitting for the second-neighbor cation-anion bonds in the wurtzite structure awaits experimental testing.

  7. Predicted bond length variation in wurtzite and zinc-blende InGaN and AlGaN alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mattila, T.; Zunger, A. [National Renewable Energy Laboratory, Golden, Colorado, 80401 (United States)

    1999-01-01

    Valence force field simulations utilizing large supercells are used to investigate the bond lengths in wurtzite and zinc-blende In{sub x}Ga{sub 1{minus}x}N and Al{sub x}Ga{sub 1{minus}x}N random alloys. We find that (i) while the first-neighbor cation{endash}anion shell is split into two distinct values in both wurtzite and zinc-blende alloys (R{sub Ga{minus}N{sub 1}}{ne}R{sub In{minus}N{sub 1}}), the second-neighbor cation{endash}anion bonds are equal (R{sub Ga{minus}N{sub 2}}=R{sub In{minus}N{sub 2}}). (ii) The second-neighbor cation{endash}anion bonds exhibit a crucial difference between wurtzite and zinc-blende binary structures: in wurtzite we find {ital two} bond distances which differ in length by 13{percent} while in the zinc-blende structure there is only {ital one} bond length. This splitting is preserved in the alloy, and acts as a fingerprint, distinguishing the wurtzite from the zinc-blende structure. (iii) The small splitting of the first-neighbor cation{endash}anion bonds in the wurtzite structure due to nonideal {ital c/a} ratio is preserved in the alloy, but is obscured by the bond length broadening. (iv) The cation{endash}cation bond lengths exhibit three distinct values in the alloy (Ga{endash}Ga, Ga{endash}In, and In{endash}In), while the anion{endash}anion bonds are split into two values corresponding to N{endash}Ga{endash}N and N{endash}In{endash}N. (v) The cation{endash}related splitting of the bonds and alloy broadening are considerably larger in InGaN alloy than in AlGaN alloy due to larger mismatch between the binary compounds. (vi) The calculated first-neighbor cation{endash}anion and cation{endash}cation bond lengths in In{sub x}Ga{sub 1{minus}x}N alloy are in good agreement with the available experimental data. The remaining bond lengths are provided as predictions. In particular, the predicted splitting for the second-neighbor cation{endash}anion bonds in the wurtzite structure awaits experimental testing. {copyright} {ital 1999

  8. Atomic Structures of Riboflavin (Vitamin B2) and its Reduced Form with Bond Lengths Based on Additivity of Atomic Radii

    CERN Document Server

    Heyrovska, Raji

    2008-01-01

    It has been shown recently that chemical bond lengths, in general, like those in the components of nucleic acids, caffeine related compounds, all essential amino acids, methane, benzene, graphene and fullerene are sums of the radii of adjacent atoms constituting the bond. Earlier, the crystal ionic distances in all alkali halides and lengths of many partially ionic bonds were also accounted for by the additivity of ionic as well as covalent radii. Here, the atomic structures of riboflavin and its reduced form are presented based on the additivity of the same set of atomic radii as for other biological molecules.

  9. C atom endohedral doping effect on the bond lengths in the crystal structure of fcc-C60

    Directory of Open Access Journals (Sweden)

    S Javanbakht

    2011-03-01

    Full Text Available Single and double equilibrium bond lengths of the fcc-C60 crystal were calculated in the absence and presence of the endohedral C atom as an impurity doped into each C60 cluster, i.e., fcc-C@C60, by means of fully-relaxed self-consistent calculations within the density functtional theory (DFT employing the full potential-augmented plane waves plus local orbital (FP-APW+lo method. The result shows that the single and double bond lengths were decreased for the doped case of fcc-C@C60 when compared with the pure fcc-C60. The reduction in the bond lengths by the carbon impurity doping is attributed to the bond alternation effect and reduction of the symmetry in the C60 molecule. The result shows that the impurity injection gives rise to change in the electron charge distribution and as a result to change in electronic properties.

  10. The role of Cu-O bond length fluctuations in the high temperature superconductivity mechanism

    Science.gov (United States)

    Deutscher, Guy

    2012-06-01

    We review three different kinds of experiments that emphasize the non-BCS, inhomogeneous aspects of superconductivity in the high Tc cuprates. The first is the existence of two different energy scales in the superconducting state, initially identified by a comparison between tunneling and Andreev-Saint-James spectroscopies [Deutscher, Nature (London) 397, 410 (1999)]. The second are EXAFS measurements of the Cu-O bond length distribution, which have shown that below a temperature T* > Tc, it becomes broader than expected from the Debye-Waller broadening and presents a split [Bianconi et al., Phys. Rev. Lett. 76, 3412 (1996)]. The third one is the effect of frozen lattice disorder on critical current and vortex pinning, which profoundly affects the pairing landscape [Gutierrez et al., Nature Mater. 6, 367 (2007)]. We then discuss how these results fit with models in which the electron-lattice interaction plays a leading role.

  11. Models for mean bonding length, melting point and lattice thermal expansion of nanoparticle materials

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.com [Department of Physics, College of Science, University of Salahaddin-Erbil, Arbil, Kurdistan (Iraq)

    2012-11-15

    Graphical abstract: Three models are derived to explain the nanoparticles size dependence of mean bonding length, melting temperature and lattice thermal expansion applied on Sn, Si and Au. The following figures are shown as an example for Sn nanoparticles indicates hilly applicable models for nanoparticles radius larger than 3 nm. Highlights: ► A model for a size dependent mean bonding length is derived. ► The size dependent melting point of nanoparticles is modified. ► The bulk model for lattice thermal expansion is successfully used on nanoparticles. -- Abstract: A model, based on the ratio number of surface atoms to that of its internal, is derived to calculate the size dependence of lattice volume of nanoscaled materials. The model is applied to Si, Sn and Au nanoparticles. For Si, that the lattice volume is increases from 20 Å{sup 3} for bulk to 57 Å{sup 3} for a 2 nm size nanocrystals. A model, for calculating melting point of nanoscaled materials, is modified by considering the effect of lattice volume. A good approach of calculating size-dependent melting point begins from the bulk state down to about 2 nm diameter nanoparticle. Both values of lattice volume and melting point obtained for nanosized materials are used to calculate lattice thermal expansion by using a formula applicable for tetrahedral semiconductors. Results for Si, change from 3.7 × 10{sup −6} K{sup −1} for a bulk crystal down to a minimum value of 0.1 × 10{sup −6} K{sup −1} for a 6 nm diameter nanoparticle.

  12. Ab initio determination of bond length dependence of the correlated valence shell Hamiltonian of CH: Comparison with semiempirical theories

    Science.gov (United States)

    Sun, Hosung; Freed, Karl F.

    1984-01-01

    The exact ab initio effective valence shell Hamiltonian, which is mimicked by semiempirical theories of valence, is calculated for CH at 11 bond lengths using quasidegenerate many-body perturbation theory to incorporate extensive correlation contributions. Least squares fits of the bond length dependence of the calculated CH matrix elements provide simple formulas which are compared with the intuitive forms introduced into semiempirical theories. Some of the semiempirical formulas, e.g., one-center, one-electron integrals and two-center, two-electron integrals, are in good agreement with our correlated ab initio calculations, while others display substantial departures. For example, the bond length dependence of one-center, two-electron integrals, which are assumed to be independent of bond length in semiempirical theories, is substantial but physically understandable. Corrections are found to the assumed proportionality of resonance and overlap integrals. The bond length dependence of nonclassical three-electron integrals is presented along with the hybrid and exchange integrals that are ignored in zero differential overlap methods.

  13. NMR study of the FH⋯F hydrogen bond. Relation between hydrogen atom position and FH⋯F bond length

    Science.gov (United States)

    Panich, A. M.

    1995-07-01

    1H and 19F NMR study of (NH 4) 3BiBr 6NH 4Br·2NH 4HF 2 shows the bifluoride ion in this compound to be asymmetric with distances r( HF) = 1.042 ± 0.002 and R( FF) = 2.373 ± 0.008 Å. Existing NMR and neutron diffraction data for the FH⋯F hydrogen bond in solids have been studied to find a relation between the position of the hydrogen atom and FH⋯F bond length. Such a relation has been established and explained in the framework of the two-dimensional dynamic model of the hydrogen bond. The dependencies of r(AH) on R(AB) for the OH⋯O and FH⋯F bonds are shown to be similar.

  14. Determination of Hydrogen Bond Structure in Water versus Aprotic Environments To Test the Relationship Between Length and Stability

    Energy Technology Data Exchange (ETDEWEB)

    Sigala, Paul A.; Ruben, Eliza A.; Liu, Corey W.; Piccoli, Paula M. B.; Hohenstein, Edward G.; Martinez, Todd J.; Schultz, Arthur J.; Herschiag, Daniel

    2015-05-06

    Hydrogen bonds profoundly influence the architecture and activity of biological macromolecules. Deep appreciation of hydrogen bond contributions to biomolecular function thus requires a detailed understanding of hydrogen bond structure and energetics and the relationship between these properties. Hydrogen bond formation energies (Delta G(f)) are enormously more favorable in aprotic solvents than in water, and two classes of contributing factors have been proposed to explain this energetic difference, focusing respectively on the isolated and hydrogen-bonded species: (I) water stabilizes the dissociated donor and acceptor groups much better than aprotic solvents, thereby reducing the driving force for hydrogen bond formation; and (II) water lengthens hydrogen bonds compared to aprotic environments, thereby decreasing the potential energy within the hydrogen bond. Each model has been proposed to provide a dominant contribution to Delta G(f), but incisive tests that distinguish the importance of these contributions are lacking. Here we directly test the structural basis of model II. Neutron crystallography, NMR spectroscopy, and quantum mechanical calculations demonstrate that O-H center dot center dot center dot O hydrogen bonds in crystals, chloroform, acetone, and water have nearly identical lengths and very similar potential energy surfaces despite Delta G(f) differences >8 kcal/mol across these solvents. These results rule out a substantial contribution from solvent-dependent differences in hydrogen bond structure and potential energy after association (model II) and thus support the conclusion that differences in hydrogen bond Delta G(f) are predominantly determined by solvent interactions with the dissociated groups (model I). These findings advance our understanding of universal hydrogen-bonding interactions and have important implications for biology and engineering.

  15. Breakdown of the first hyperpolarizability/bond-length alternation parameter relationship

    Science.gov (United States)

    Murugan, N. Arul; Kongsted, Jacob; Rinkevicius, Zilvinas; Ågren, Hans

    2010-01-01

    We have investigated the dependence of the static first hyperpolarizability on the bond-length alternation (BLA) parameter. Our analysis indicates that the validity of the first hyperpolarizability/BLA parameter relationship is restricted to the no-field, vacuum, limit, while it successively breaks down along with increasing polarity of a surrounding medium, becoming invalid, for instance, in an aqueous solution. This contention is based on a series of TD-DFT, TD-DFT/PCM and hybrid TD-DFT/MM calculations of the first hyperpolarizability for a set of molecular configurations generated from Car–Parrinello hybrid QM/MM simulations of the stilbazolium merocyanine chromophore in chloroform and water solvents, and on a rationalization by means of the two-state model for the first hyperpolarizability. The BLA dependence of the three parameters entering the two-state model is shown to be qualitatively different in vacuum and in solvents. Particularly, in the vacuum case, the difference between ground and excited state dipole moments goes to zero for a vanishing BLA, which is not true in the presence of an aqueous medium. In the aqueous medium, an opposing behavior of the parameters involved in the two-state model results in an almost constant first hyperpolarizability with varying BLA parameter. PMID:20823263

  16. Bond-length analysis of the omega structure in Ti,Zr,Hf and their alloys: experimental data, new correlations and implications for chemical bonding models

    Energy Technology Data Exchange (ETDEWEB)

    Grad, G.B.; Benites, G.M. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche; Aurelio, G. [Departamento de Fisica, Universidad del Comahue, 8300, Neuquen (Argentina); Fernandez Guillermet, A. [Centro Atomico Bariloche, 8400, San Carlos de Bariloche (Argentina)

    1999-12-15

    An analysis is performed of the experimental information on the key interatomic distances (IDs) of the AlB{sub 2} type structure, the so-called omega ({omega}) phase in Ti and Zr, as well as in Ti-V and Zr-Nb alloys. Various remarkable correlations are found between these IDs and standard measures of the atomic size, and with Pauling's bond-lengths. These observations are discussed in the light of the phenomenological bonding pictures of the {omega} structure, and with our recent ab initio calculations of the electronic structure of this phase. (orig.)

  17. Influence of bond length variation on correlated static exchange potential: A case study in e--N2 scattering

    Science.gov (United States)

    Ghose, Keya Basu; Pal, Sourav

    1994-03-01

    We discuss in this note how the correlated static exchange potential changes with bond length for N2 molecule where the earlier extensive results at equilibrium exist. We have used many-body coupled cluster technique for this study. Its relevance to e--N2 scattering is also discussed.

  18. Effect of magnetic field on energy spectrum and localization of electron in CdS/HgS/CdS/HgS/CdS multilayered spherical nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Holovatsky, V.A., E-mail: ktf@chnu.edu.ua; Bernik, I.B.; Yakhnevych, M. Ya.

    2017-03-01

    The theoretical investigation of magnetic field effect on energy spectrum and localization of the electron and oscillator strengths of intraband quantum transitions in the nanostructure CdS/HgS/CdS/HgS/CdS is performed. The calculations are made in the framework of effective mass approximation and rectangular potential barriers model using the method of the expansion of quasi-particle wave functions over the complete basis of functions obtained as the exact solutions of the Schrodinger equation for the electron in the nanostructure without the magnetic field. It is shown that the magnetic field violates the spherical symmetry of the system and takes off the degeneration of energy spectrum with respect to the magnetic quantum number. The energy of the electron in the states with m≥0 increases when magnetic field enhances; for the states with m<0 these dependences are non-monotonous (decreasing at first and then increasing). Moreover, the ground state of electron is formed alternately by the states with m=0, −1, −2, …. Magnetic field influences on the distribution of quasi-particle density. It is shown that the electron significantly changes its localization in the nanostructure with two potential wells tunneling through the potential barrier under the effect of magnetic field, changing the oscillator strengths of intraband quantum transitions.

  19. Effect of magnetic field on energy spectrum and localization of electron in CdS/HgS/CdS/HgS/CdS multilayered spherical nanostructure

    Science.gov (United States)

    Holovatsky, V. A.; Bernik, I. B.; Yakhnevych, M. Ya.

    2017-03-01

    The theoretical investigation of magnetic field effect on energy spectrum and localization of the electron and oscillator strengths of intraband quantum transitions in the nanostructure CdS/HgS/CdS/HgS/CdS is performed. The calculations are made in the framework of effective mass approximation and rectangular potential barriers model using the method of the expansion of quasi-particle wave functions over the complete basis of functions obtained as the exact solutions of the Schrodinger equation for the electron in the nanostructure without the magnetic field. It is shown that the magnetic field violates the spherical symmetry of the system and takes off the degeneration of energy spectrum with respect to the magnetic quantum number. The energy of the electron in the states with m≥0 increases when magnetic field enhances; for the states with m<0 these dependences are non-monotonous (decreasing at first and then increasing). Moreover, the ground state of electron is formed alternately by the states with m=0, -1, -2, …. Magnetic field influences on the distribution of quasi-particle density. It is shown that the electron significantly changes its localization in the nanostructure with two potential wells tunneling through the potential barrier under the effect of magnetic field, changing the oscillator strengths of intraband quantum transitions.

  20. The estimation of CO bond length changes in the excited states of transition metal carbonyls

    Science.gov (United States)

    Morrison, Sara L.; Turner, James J.

    1994-01-01

    Advances in vibrational spectroscopy have led to increased knowledge of shortlived excited states. In the case of transition metal carbonyl compounds, time-resolved infrared spectra can be measured directly. The CO energy factored force constants are used to estimate the CO bond length distortions upon excitation. The new empirical relationship rCO = 1.674 - 0.184 ln kCO allows excited states CO bond lenghts to be calculated with a standard deviation of ±0.005 Å. For energy factored systems it is deemed unnecessary to calculate pseudodiatomic frequencies ( vPD) from the potential energy distribution.

  1. Electron-electron interactions in the chemical bond: ``1/3” Effect in the bond length of hydrogen molecule

    Indian Academy of Sciences (India)

    P Ganguly

    2001-10-01

    The prominent ``1/3” effect observed in the Hall effect plateaus of twodimensional electron gas (2DEG) systems has been postulated to indicating 1/3 fractional charge quasiparticle excitations arising from electron-electron interactions. Tunneling shot-noise experiments on 2DEF exhibiting fractional quantum Hall effect (FQHE) shows evidence for tunnelling of particles with and /3 charges for a constant band mass. A ``1/3” effect in the hydrogen molecule is seen in as much as its internuclear distance, - = - + +, with |+/-| = 1/3. This is examined in terms of electron-electron interactions involving electron- and hole quasiparticles, (-) and (ℎ+), equivalent to those observed in FQHE shot-noise experiments. The (/) ratio of the (-) and (ℎ+) quasiparticles is kept at 1: -3. Instead of a 2DEG, these particles are treated as being in flat Bohr orbits. A treatment in the language of charge-flux tube composites for the hydrogen atom as well as the hydrogen molecule is attempted. Such treatment gives important insights into changes in chemical potential and bond energy on crossing a phase boundary during the atom-bond transition as well as on models for FQHE itself.

  2. Development of bond-length alternation in very large carbon rings: LDA pseudopotential results

    Science.gov (United States)

    Bylaska, Eric J.; Weare, John H.; Kawai, Ryoichi

    1998-09-01

    Carbon rings Cn and infinite chains C∞ are investigated by molecular-orbital and band-structure calculations within the local-density approximation. Carbon rings C4N (N=20). For the infinite carbon chain uniform Brillouin-zone sampling with an even number of points Ns gives bond alternation. An odd number of sampling points gives no bond alternation for less than Ns=41. In the large Ns limit even and odd sampling lead to an upper and lower bound of 0.070a0 and 0.065a0 for bond alternation and 0.021-0.090 millihartrees/atom for condensation energy.

  3. [Dissolution, absorption and bioaccumulation in gastrointestinal tract of mercury in HgS-containing traditional medicines Cinnabar and Zuotai].

    Science.gov (United States)

    Zheng, Zhi-yuan; Li, Cen; Zhang, Ming; Yang, Hong-xia; Geng, Lu-jing; Li, Lin-shuai; Du, Yu-zhi; Wei, Li-xin

    2015-06-01

    α-HgS is the main component of traditional Chinese medicine cinnabar, while β-HgS is the main component of Tibetan medicine Zuotai. However, there was no comparative study on the dissolution and absorption in gastrointestinal tract and bioaccumulation in organs of mercury in Cinnabar, Zuotai, α-HgS and β-HgS. In this study, the dissolution process of the four compounds in the human gastrointestinal tract was simulated to determine the mercury dissolutions and compare the mercury dissolution of different medicines and the dissolution-promoting capacity of different solutions. To explore the absorption and bioaccumulation of cinnabar and Zuotai in organisms, mice were orally administered with clinical equivalent doses cinnabar and Zuotai. Meanwhile, a group of mice was given α-HgS and β-HgS with the equivalent mercury with cinnabar, while another group was given β-HgS and HgCl2 with the equivalent mercury with Zuotai. The mercury absorption and bioaccumulation capacities of different medicines in mice and their mercury bioaccumulation in different tissues and organs were compared. The experimental results showed a high mercury dissolutions of Zuotai in artificial gastrointestinal fluid, which was followed by β-HgS, cinnabar and α-HgS. As for the mercury absorption and bioaccumulation in mice, HgCl2 was the highest, β-HgS was the next, and a-HgS was slightly higher than cinnabar. The organs with the mercury bioaccumulation from high to low were kidney, liver and brain. This study is close to clinical practices and can provide reference for the clinical safe medication as well as a study model for the safety evaluation on heavy metal-containing medicines by observing the mercury dissolution, absorption, distribution and accumulation of mercury-containing medicines cinnabar and zuotai.

  4. Atomic Structures of the Amino Acids, Glycine, Alanine and Serine and Their Tripeptide, with Bond Lengths as Sums of Atomic Covalent Radii

    CERN Document Server

    Heyrovska, Raji

    2008-01-01

    Recently, the bond lengths of the molecular components of nucleic acids and of caffeine and related molecules were shown to be sums of the appropriate covalent radii of the adjacent atoms. Thus, each atom was shown to have its specific contribution to the bond length. This enabled establishing their atomic structures for the first time. In this work, the known bond lengths for amino acids and the peptide bond are similarly shown to be sums of the atomic covalent radii. Based on this result, the atomic structures of glycine, alanine and serine and their tripeptide have been presented.

  5. Phase Transition and EOS of Cinnabar (α-HgS) at High Pressure and High Temperature

    Institute of Scientific and Technical Information of China (English)

    FAN Da-Wei; ZHOU Wen-Ge; LIU Cong-Qiang; WAN Fang; XING Yin-Suo; LIU Jing; LI Yan-Chun; XIE Hong-Sen

    2009-01-01

    @@ Phase relations and equation of state (EOS) of natural cinnabar (α-HgS) are investigated by high-pressure and high-temperature synchrotron x-ray powder diffraction. The unambiguous cinnabar-rocksalt structure phase boundaries are determined to be Plower(Gpa)=15.54-0.014T(℃) and Pupper(Gpa)= 23.84 - 0.014T(℃) at 300--623K. With K' axed at 4, we obtain K0 = 37(4) Gpa, ( K/ T)p=-0.025(2) GPaK-1, and α0= 3.79(20)× 10-5 K-1 for the cinnabar phase of α-HgS. The ( K/ T)p and α0 of cinnabar phase are obtained for the first time. A nearly isotropic compression of cinnabar phase is observed by linear regressions.

  6. Communication: Bond length alternation of conjugated oligomers: Another step on the fifth rung of Perdew's ladder of functional.

    Science.gov (United States)

    Chabbal, Sylvain; Jacquemin, Denis; Adamo, Carlo; Stoll, Hermann; Leininger, Thierry

    2010-10-21

    In this work, we present the application of the hybrid short-range density functional theory/long-range MP2 energy gradients to the bond length alternation in polymethineimine and polyacetylene conjugated oligomers. Compared to other density functional calculations, our results are quite superior, even to fourth rung functionals, usually better than MP2 and very close to the available CCSD(T) values.

  7. Communication: Bond length alternation of conjugated oligomers: Another step on the fifth rung of Perdew's ladder of functional

    Science.gov (United States)

    Chabbal, Sylvain; Jacquemin, Denis; Adamo, Carlo; Stoll, Hermann; Leininger, Thierry

    2010-10-01

    In this work, we present the application of the hybrid short-range density functional theory/long-range MP2 energy gradients to the bond length alternation in polymethineimine and polyacetylene conjugated oligomers. Compared to other density functional calculations, our results are quite superior, even to fourth rung functionals, usually better than MP2 and very close to the available CCSD(T) values.

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

    Science.gov (United States)

    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)).

  9. Studies of EXAFSSpectra using Copper (II) Schiff Base complexes and Determination of Bond lengths Using Synchrotron Radiation

    Science.gov (United States)

    Mishra, A.; Vibhute, V.; Ninama, S.; Parsai, N.; Jha, S. N.; Sharma, P.

    2016-10-01

    X-ray absorption fine structure (XAFS) at the K-edge of copper has been studied in some copper (II) complexes with substituted anilines like (2Cl, 4Br, 2NO2, 4NO2 and pure aniline) with o-PDA (orthophenylenediamine) as ligand. The X-ray absorption measurements have been performed at the recently developed BL-8 dispersive EXAFS beam line at 2.5 GeV Indus-2 Synchrotron Source at RRCAT, Indore, India. The data obtained has been processed using EXAFS data analysis program Athena.The graphical method gives the useful information about bond length and also the environment of the absorbing atom. The theoretical bond lengths of the complexes were calculated by using interactive fitting of EXAFS using fast Fourier inverse transformation (IFEFFIT) method. This method is also called as Fourier transform method. The Lytle, Sayers and Stern method and Levy's method have been used for determination of bond lengths experimentally of the studied complexes. The results of both methods have been compared with theoretical IFEFFIT method.

  10. Distinguishing the Effects of Bond-Length Alternation versus Bond-Order Alternation on the Nonlinear Optical Properties of π-Conjugated Chromophores

    KAUST Repository

    Gieseking, Rebecca L.

    2015-06-18

    Understanding the relationships between the molecular nonlinear optical (NLO) properties and the bond-length alternation (BLA) or π-bond-order alternation (BOA) along the molecular backbone of linear π-conjugated systems has proven widely useful in the development of NLO organic chromophores and materials. Here, we examine model polymethines to elucidate the reliability of these relationships. While BLA is solely a measure of molecular geometric structure, BOA includes information pertaining to the electronic structure. As a result, BLA is found to be a good predictor of NLO properties only when optimized geometries are considered, whereas BOA is more broadly applicable. Proper understanding of the distinction between BLA and BOA is critical when designing computational studies of NLO properties, especially for molecules in complex environments or in nonequilibrium geometries. © 2015 American Chemical Society.

  11. Variation of the Pole Length in Pole-Oriented Bonded Rings due to the Location and Number of Injection Points

    Directory of Open Access Journals (Sweden)

    Katharina H. Kurth

    2017-01-01

    Full Text Available Polymer bonded magnets are compounds consisting of a polymer matrix with embedded hard magnetic filler particles. These materials are mainly used in applications in actor or sensor technology. One example is the application as multipolar encoder wheel in magnetic sensors. Depending on the application different requirements have to be fulfilled, such as a high pole length accuracy and repeatability. This investigation deals with the production of multipolar rings in the injection molding process for sensor applications and influences of the design of the gating system on the pole length accuracy. It is shown that the number of injection points and developing weld lines, as well as the positioning of the injection points, has a major influence on the magnetization characteristics of the molded rings. In general, a positioning of injection points and weld lines in the pole pitch and higher number of injection points lead to rings with a high reproduction accuracy of the pole length of the mold.

  12. Understanding Pd-Pd bond length variation in (PNP)Pd-Pd(PNP) dimers.

    Science.gov (United States)

    Walensky, Justin R; Fafard, Claudia M; Guo, Chengyun; Brammell, Christina M; Foxman, Bruce M; Hall, Michael B; Ozerov, Oleg V

    2013-03-04

    Analysis of the structures of three (PNP)Pd-Pd(PNP) dimers [where PNP stands for anionic diarylamido/bis(phosphine) pincer ligands] has been carried out with the help of single-crystal X-ray diffractometry and density functional theory (DFT) calculations on isolated molecules. The three dimers under study possess analogous ancillary ligands; two of them differ only by an F versus Me substituent in a remote (five bonds away from Pd) position of the pincer ligand. Despite these close similarities, X-ray structural determinations revealed two distinct structural motifs: a highly symmetric molecule with a long Pd-Pd bond or a highly distorted molecule with Pd-Pd bonds ca. 0.14 Å shorter. DFT calculations on a series of (PNP)Pd-Pd(PNP) dimers (as molecules in the gas phase) confirmed the existence of these distinct minima for dimers carrying large isopropyl substituents on the P-donor atoms (as in the experimental structure). These minima are nearly isoergic conformers. Evidently, the electronically preferred symmetric structure for the dimer (with a square-planar environment about Pd and a linear N-Pd-Pd-N vector) is not sterically possible with the preferred Pd-Pd distance. Thus, the minima correspond to either a symmetric structure with a long Pd-Pd bond distance or a structure with a short Pd-Pd distance but with substantial distortions in the Pd coordination environment to alleviate steric conflict. This notion is supported by finding only a single minimum (symmetric and with short Pd-Pd bonds) for each of the dimers carrying smaller substituents (H or Me) on the P atoms, regardless of the remote substitution.

  13. Two states are not enough: quantitative evaluation of the valence-bond intramolecular charge-transfer model and its use in predicting bond length alternation effects.

    Science.gov (United States)

    Jarowski, Peter D; Mo, Yirong

    2014-12-15

    The structural weights of the canonical resonance contributors used in the Two-state valence-bond charge-transfer model, neutral (N, R1) and ionic (VB-CT, R2), to the ground states and excited states of a series of linear dipolar intramolecular charge-transfer chromophores containing a buta-1,3-dien-1,4-diyl bridge have been computed by using the block-localized wavefunction (BLW) method at the B3LYP/6-311+G(d) level to provide the first quantitative assessment of this simple model. Ground- and excited-state analysis reveals surprisingly low ground-state structural weights for the VB-CT resonance form using either this Two-state model or an expanded Ten-state model. The VB-CT state is found to be more prominent in the excited state. Individual resonance forms were structurally optimized to understand the origins of the bond length alternation (BLA) of the bridging unit. Using a Wheland energy-based weighting scheme, the weighted average of the optimized bond lengths with the Two-state model was unable to reproduce the BLA features with values 0.04 to 0.02 Å too large compared to the fully delocalized (FD) structure (BLW: ca. -0.13 to -0.07 Å, FD: ca. -0.09 to -0.05 Å). Instead, an expanded Ten-state model fit the BLA values of the FD structure to within only 0.001 Å of FD. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Quantification of the push-pull effect in substituted alkynes. Evaluation of +/-I/+/-M substituent effects in terms of C[triple bond]C bond length variation.

    Science.gov (United States)

    Kleinpeter, Erich; Frank, Andrea

    2009-06-18

    (13)C chemical shifts of alkynes, published to date, were computed at the DFT (B3LYP/6-311G*) level of theory and compared with the experimental delta values, and the agreement was employed as a measure of quality for the underlying structures. For the corresponding global minima structures, thus obtained, the occupation quotients of antibonding pi* and bonding pi orbitals (pi*(C[triple bond]C)/pi(C[triple bond]C)) and the bond lengths (d(C[triple bond]C)) of the central C[triple bond]C triple bond were computed and correlated to each other. The linear dependence obtained for the two push-pull parameters d(C[triple bond]C) and pi*(C[triple bond]C)/pi(C[triple bond]C) quantifies changes in the push-pull effect of substituents while deviations from the best line of fit indicate and ascertain quantitatively to what extend the inductive (+/-I) substituent effect changes with respect to the bond length of the C[triple bond]C triple bond.

  15. Deduction of bond length changes of symmetric molecules from experimental vibrational progressions, including a topological mass factor.

    Science.gov (United States)

    Su, Jing; Wei, Fan; Schwarz, W H E; Li, Jun

    2012-12-20

    The change ΔR(x) of bond length R(x) for atom X in a molecule upon electronic transition can be derived from the intensities I(i) of the vibrational stretching progression v = 0 → i of the electronic absorption or emission spectrum. In many cases, a simple model is sufficient for a reasonable estimate of ΔR(x). For symmetric molecules, however, conceptual problems in the literature of many decades are evident. The breathing modes of various types of symmetric molecules X(n) and AX(n) (A at the center) are here discussed. In the simplest case of a harmonic vibration of the same mode in the initial and final electronic states, we obtain ΔR(x) ≈ [2S/(ωm(x))](1/2)/w(1/2) (all quantities in atomic units). ω and S are respectively the observed vibrational quanta and the Huang-Rhys factor (corresponding, e.g., to the vibrational intensity ratio I(1)/I(0) ≈ S), m(x) is the mass of vibrating atom X, and w is a topological factor for molecule X(n) or AX(n). The factor 1/w(1/2) in the expression for ΔR(x) must not be neglected. The spectra and bond length changes of several symmetric molecules AX(n) and X(n) are discussed. The experimental bond length changes correctly derived with factor 1/w(1/2) are verified by reliable quantum chemical calculations.

  16. Observation of Ultrafast Bond-length Expansion at the Initial Stage of Laser Ablation by Picosecond Time-resolved EXAFS

    Science.gov (United States)

    Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi; Nakano, Hidetoshi

    We have demonstrated a time-resolved extended X-ray absorption fine structure (EXAFS) technique by using a femtosecond laser produced plasma soft X-ray source. By applying this technique to the measurement of the initial stage of the laser ablation in Si foil, we were able to observe a slight shortening of the EXAFS oscillation period. This result suggests that the Si-Si atomic bond length expands as a result of the solid-liquid phase transition in Si. The realization of this technique is the first step toward understanding atomic structural dynamics during a chemical reaction.

  17. Assessment of recently developed density functional approaches for the evaluation of the bond length alternation in polyacetylene

    Science.gov (United States)

    Jacquemin, Denis; Perpète, Eric. A.; Ciofini, Ilaria; Adamo, Carlo

    2005-04-01

    The bond length alternation (BLA) of increasingly long polyacetylene oligomers has been computed using various wavefunction methods of increasing accuracy and several DFT models, including standard GGA and the most-recent meta-GGA and hybrid functionals. Our results show the meta-GGA functionals do not offer any significant improvement with respect to the GGA approaches, both providing too small values for the BLA. More accurate results are obtained with hybrid approaches, where, instead, the percent of HF exchange rules the quantitative result. In particular, hybrids including 25% of HF exchange are the most accurate, whereas TPSSh, O3LYP, τ-HCTHh provide only poor estimates.

  18. Application of the linear/exponential hybrid force field scaling scheme to the bond length alternation modes of polyacetylene

    Science.gov (United States)

    Yang, Shujiang; Kertesz, Miklos

    2006-12-01

    The two bond length alternation related backbone carbon-carbon stretching Raman active normal modes of polyacetylene are notoriously difficulty to predict theoretically. We apply our new linear/exponential scaled quantum mechanical force field scheme to tackle this problem by exponentially adjusting the decay of the coupling force constants between backbone stretchings based on their distance which extends over many neighbors. With transferable scaling parameters optimized by least squares fitting to the experimental vibrational frequencies of short oligoenes, the scaled frequencies of trans-polyacetylene and its isotopic analogs agree very well with experiments. The linear/exponential scaling scheme is also applicable to the cis-polyacetylene case.

  19. Intramolecular bond length dependence of the anisotropic dispersion coefficients for interactions of rare gas atoms with N2, CO, Cl2, HCl and HBr

    Science.gov (United States)

    Hettema, Hinne; Wormer, Paul E. S.; Thakkar, Ajit J.

    Ab initio many body perturbation theory is used to calculate the imaginary frequency multipole polarizabilities of N2, Cl2, CO, HCl and HBr as a function of bond length. These are combined with previously calculated dynamic polarizabilities for rare gas atoms to obtain the intramolecular bond length dependence of the anisotropic dispersion and induction coefficients through R-8 for AB-X (AB = N2, Cl2, CO, HCl, HBr and X = He, Ne, Ar, Kr, Xe) interactions.

  20. Levitation effect: role of symmetry and dependence of diffusivity on the bond length of homonuclear and heteronuclear diatomic species.

    Science.gov (United States)

    Sharma, Manju; Yashonath, S

    2011-04-07

    Molecular dynamics investigation of model diatomic species confined to the α-cages of zeolite NaY is reported. The dependence of self-diffusivity on the bond length of the diatomic species has been investigated. Three different sets of runs have been carried out. In the first set, the two atoms of the diatomic molecule interact with the zeolite atoms with equal strength (example, O(2), the symmetric case). In the second and third sets which correspond to asymmetric cases, the two atoms of the diatomic molecule interact with unequal strengths (example, CO). The result for the symmetric case exhibits a well-defined maximum in self-diffusivity for an intermediate bond length. In contrast to this, the intermediate asymmetry leads to a less pronounced maximum. For the large asymmetric case, the maximum is completely absent. These findings are analyzed by computing a number of related properties. These results provide a direct confirmation at the microscopic level of the suggestion by Derouane that the supermobility observed experimentally by Kemball has its origin in the mutual cancellation of forces. The maximum in diffusivity from molecular dynamics is seen at the value predicted by the levitation effect. Further, these findings suggest a role for symmetry in the existence of a diffusivity maximum as a function of diameter of the diffusant often referred to as the levitation effect. The nature of the required symmetry for the existence of anomalous diffusivity is interaction symmetry which is different from that normally encountered in crystallography.

  1. Bond-length variation in InxGa1-xAs/InP strained epitaxial layers

    Science.gov (United States)

    Romanato, F.; de Salvador, D.; Berti, M.; Drigo, A.; Natali, M.; Tormen, M.; Rossetto, G.; Pascarelli, S.; Boscherini, F.; Lamberti, C.; Mobilio, S.

    1998-06-01

    Tensile and compressive InxGa1-xAs epilayers grown on [001] InP substrates have been analyzed by fluorescence-detected x-ray-absorption fine structure in order to investigate the length variation suffered by Ga-As and In-As atomic bonds under epitaxial strain. A morphological and structural analysis had previously been performed in order to select only pseudomorphic samples with high lattice quality. A clear variation of the nearest-neighbor distances proportional to the tetragonal distortion of the film has been detected. We discuss the relationship between the long- and short-range descriptions of strain accommodation in the framework of an analytical model.

  2. Metastable innershell molecular state (MIMS) III: The universal binding energy and bond length of the homonucleus K-shell MIMS

    Science.gov (United States)

    Bae, Young K.

    2016-03-01

    This paper reports the discovery of a universal Z2-dependency of the binding energy of the homonucleus K-shell MIMS (K-MIMS: Metastable Innershell Molecular State bound by K-shell electrons), which has been established by analyzing extensive existing experimental data over several decades. An intuitive analytical theory on the K-MIMS has been developed for the homologous molecules to the He*2 excimer, which elucidates the universal Z-dependent behavior of the K-MIMS. The theory predicts a 1 / Z-dependency of the K-MIMS bond length, which is in agreement with the quasimolecule sizes estimated from the x-ray generation cross-sections in H-like Bi82+ and U91+ impact on Au solids.

  3. Atomic ordering and systematics of bonding lengths in the Ti-V omega phase: a neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Benites, G.M.; Guillermet, A.F. [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Centro Atomico Bariloche (Argentina); Aurelio, G. [Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); Cuello, G.J.; Bermejo, F.J. [Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas y Tecnicas, Serrano 123, Madrid E-28006 (Spain)

    1999-03-04

    A new model describing the structural and bonding properties of the omega ({Omega}) phase in Zr-Nb alloys has recently been presented [12]. This model, which was aimed at explaining the composition dependence of the bonding lengths, predicts that the {Omega} phase is ordered, i.e., that some crystallographic sites are preferentially occupied by Zr atoms. Such feature, which should in principle be observed in other, related {Omega} phases, has not yet been tested against direct measurements. This problem has now been studied in the Ti-V system, which is the analogue of Zr-Nb in the 3d-transition series. Neutron diffraction measurements have been performed in quenched Ti-V alloys with V contents between 14 and 17 at.%. The diffraction spectra have been analysed using the Rietveld method, and a systematic analysis is reported here of the possibility of deviations from the random occupation of the two sublattices which are distinguished in the {Omega} structure. In addition, these new diffraction data are used in an evaluation of the shortest interatomic distances which are relevant for a comparison with the predictions of the model of Grad et al. (orig.) 28 refs.

  4. 共价键长的变化规律及计算%Variation Rule of Covalent Bond Length and Its Calculation Method

    Institute of Scientific and Technical Information of China (English)

    徐永群; 陈年友

    2001-01-01

    研究了共价键长的变化规律,提出了两个影响键长的参数,即配位体的半径与中心原子半径之比Rratio和由中心原子组成的基团的拓扑指数F2,用BP神经网络法逼近了50个、预测了11个简单无机分子中非含氢原子键的键长,其计算误差基本上在2pm以内。%The variation rule of covalent bond lengths is investigated.Two parameters which influence covalent bond lengths are presented: the radius ratio of the ligand to the centre atom and the topological index of the group of centre atom.With BP neural networks, 50 bond lengths have been approached and other 11 bond lengths have been forecasted. Errors of calculated bond lengths is almost within 2pm.

  5. Raman spectroscopic determination of the length, strength, compressibility, Debye temperature, elasticity, and force constant of the C-C bond in graphene.

    Science.gov (United States)

    Yang, X X; Li, J W; Zhou, Z F; Wang, Y; Yang, L W; Zheng, W T; Sun, Chang Q

    2012-01-21

    From the perspective of bond relaxation and bond vibration, we have formulated the Raman phonon relaxation of graphene, under the stimuli of the number-of-layers, the uni-axial strain, the pressure, and the temperature, in terms of the response of the length and strength of the representative bond of the entire specimen to the applied stimuli. Theoretical unification of the measurements clarifies that: (i) the opposite trends of the Raman shifts, which are due to the number-of-layers reduction, of the G-peak shift and arises from the vibration of a pair of atoms, while the D- and the 2D-peak shifts involve the z-neighbor of a specific atom; (ii) the tensile strain-induced phonon softening and phonon-band splitting arise from the asymmetric response of the C(3v) bond geometry to the C(2v) uni-axial bond elongation; (iii) the thermal softening of the phonons originates from bond expansion and weakening; and (iv) the pressure stiffening of the phonons results from bond compression and work hardening. Reproduction of the measurements has led to quantitative information about the referential frequencies from which the Raman frequencies shift as well as the length, energy, force constant, Debye temperature, compressibility and elastic modulus of the C-C bond in graphene, which is of instrumental importance in the understanding of the unusual behavior of graphene.

  6. On the variation of bond length during large-amplitude bending from electron diffraction: the case of CaCl 2

    Science.gov (United States)

    Hargittai, Magdolna; Veszprémi, Tamás; Pasinzki, Tibor

    1994-09-01

    All geometrical parameters, including bond lengths, are influenced by large-amplitude vibrations. The magnitude of this effect was examined for metal dihalides performing large-amplitude bending motions, using CaCl 2 as an example. By using quantum chemical calculations it was shown that the effect of bending on the bond length is very sensitive to the choice of basis set. A dynamic electron diffraction analysis, augmented with quantum chemical calculations, revealed that the effect of bending on the bond length is of moderate magnitude within experimental error. This fact contrasts with the consequences of other motions, in particular stretching, that must always be accounted for in any meaningful comparison of experimental and computed structures.

  7. Linear optical properties and their bond length dependence of yttrium bromide from ab initio and density functional theory calculations

    Energy Technology Data Exchange (ETDEWEB)

    Alipour, Mojtaba, E-mail: malipour@shirazu.ac.ir [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Mohajeri, Afshan, E-mail: amohajeri@shirazu.ac.ir [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

    2011-08-25

    Graphical abstract: The electronic properties such as the static dipole polarizability, anisotropy of the polarizability, and dipole moment of yttrium bromide, YBr (X{sup 1}{Sigma}) have been theoretically studied. Highlights: {yields} Conventional ab initio and density functional theory methods were employed to study linear optical properties of YBr molecule. {yields} Properties derivatives and their level of theory dependence were studied. {yields} Electron correlation effects and rovibrational corrections have also been discussed. - Abstract: We have employed conventional ab initio and density functional theory methods to study the electronic properties such as the mean static dipole polarizability, {alpha}-bar, anisotropy of the polarizability, {Delta}{alpha}, and dipole moment, {mu}, of yttrium bromide. The bond length dependence of properties is determined at different levels of theory and appropriate expansions around experimental internuclear distance have been presented. Moreover, the first and second geometrical derivatives for each property are quantified and their level of theory dependence has been analyzed. To study the effect of molecular rotation and vibration on the electronic properties, the rovibrational corrections have also been carried out. It is found that these corrections are less pronounced for considered properties of YBr. In all calculations, the electron correlation effects have been considered and discussed. The obtained results show that the electron correlation is more significant in the calculation of the mean and the anisotropy of dipole polarizability.

  8. A study of hydrogen-bond dynamics in carboxylic acids by NMR T1 measurements: isotope effects and hydrogen-bond length dependence

    Science.gov (United States)

    Agaki, T.; Imashiro, F.; Terao, T.; Hirota, N.; Hayashi, S.

    1987-08-01

    Proton (deuteron) transfer of hydrogen bonds in benzoic, glutaric and p-formylbenzoic acids was studied by proton (deuteron) T1 measurements. Deuteration of carboxylic protons was found to increase the barriers to classical proton jumping as well as quantum-mechanical tunneling. The former barriers increase as the hydrogen-bond distance increases.

  9. Bond length variation in In0.25Ga0.75As/InP epitaxial layers thicker than the critical thickness

    Science.gov (United States)

    Tormen, M.; De Salvador, D.; Natali, M.; Drigo, A.; Romanato, F.; Rossetto, G.; Boscherini, F.; Mobilio, S.

    1999-09-01

    We address the issue of the local structure in an epitaxial semiconductor thin film undergoing strain relaxation due to extended defects when the critical thickness for their introduction is exceeded. The nearest neighbor environment is probed by x-ray absorption fine structure spectroscopy. The particular system studied is a set of In0.25Ga0.75As films grown on InP(001) of increasing thickness; the thicknesses were chosen so as to obtain a varying degree of relaxation, ranging from pseudomorphic growth to completely relaxed state. The samples have been thoroughly characterized with complementary structural techniques and the residual strain is measured by x-ray diffraction. We find that the Ga-As bond length exhibits a linear decrease with decreasing residual strain. By comparing these results with previous studies on bond lengths in pseudomorphic InxGa1-xAs films as a function of concentration we conclude that the bond lengths have an identical behavior as a function of the mean residual strain independently from its elastic or plastic origin. This result is reproduced by an analytical model based on the transfer of the mean macroscopic deformation at a local level. The broadening of the bond length distribution induced by extended defects is also discussed, concluding that it is not experimentally dectable.

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

    Science.gov (United States)

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

    2016-06-01

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

  11. Na-induced bonding and bond-length changes for CO on Pt(111): A near-edge x-ray-absorption fine-structure study

    Energy Technology Data Exchange (ETDEWEB)

    Sette, F.; Stoehr, J.; Kollin, E.B.; Dwyer, D.J.; Gland, J.L.; Robbins, J.L.; Johnson, A.L.

    1985-03-04

    Near-edge x-ray absorption fine-structure studies above the C and O K edges for CO on Pt(111) reveal a 4-eV shift of the sigma shape resonance when Na(0.2 monolayer) is coabsorbed. This allows determination of a Na-induced (0.12 +- 0.03)-A expansion of the C-O bond. Na does not affect the vertical molecular orientation on the surface. Reduction and broadening of the 1s..-->..2..pi..( resonance and the CO bond lengthening in the presence of Na signifies substantially increased metal to CO backbonding.

  12. Electron-correlation effects on the static longitudinal polarizability of polymeric chains. II. Bond-length-alternation effects

    Science.gov (United States)

    Champagne, Benoît; Mosley, David H.; Vračko, Marjan; André, Jean-Marie

    1995-08-01

    Ab initio calculations of the static longitudinal polarizability of different molecular hydrogen model chains have been carried out at different levels of approximation to investigate the effects of including electron correlation as well as the variation of these effects as a function of the bond-length alternation of the systems. First, the coupled and uncoupled Hartree-Fock schemes have been employed. To assess the electron-correlation effects, the size-consistent Mo/ller-Plesset treatments limited to second (MP2), third (MP3), and fourth (MP4) order in electron-electron interactions, as well as the coupled-cluster techniques including all double substitutions (CCD), all single and double substitutions (CCSD), and all single and double substitutions with a perturbational estimate of the connected triple excitations [CCSD(T)] have been used. Within the MP4 treatment, a decomposition of the electron-correlation corrections according to the different classes of substitutions and different order highlights the relatively greater importance of the double substitutions at second and third orders. The main findings are that (i) the coupled Hartree-Fock (CHF) technique overestimates the asymptotic static longitudinal polarizability per unit cell for the three types of H2 chains under investigation; (ii) larger basis sets have to be employed when including electron correlation effects, otherwise, the correction is overestimated; (iii) these basis-set effects on the electron-correlation correction are enhanced in the case of the less alternating chains; (iv) using a sufficiently large atomic basis set, at the Mo/ller-Plesset or CCSD(T) levels, the more conjugated the chains, the less the relative magnitude of the electron-correlation correction to the CHF value, whereas using the CCD and CCSD techniques, these relative electron-correlation corrections slightly increase in the case of the less alternating molecular hydrogen chains; and (v) the more conjugated the systems

  13. Bond length and electric current oscillation of long linear carbon chains: Density functional theory, MpB model, and quantum spin transport studies

    Science.gov (United States)

    Oeiras, R. Y.; da Silva, E. Z.

    2014-04-01

    Carbon linear atomic chains attached to graphene have experimentally been produced. Motivated by these results, we study the nature of the carbon bonds in these nanowires and how it affects their electrical properties. In the present study we investigate chains with different numbers of atoms and we observe that nanowires with odd number of atoms present a distinct behavior than the ones with even numbers. Using graphene nanoribbons as leads, we identify differences in the quantum transport of the chains with the consequence that even and odd numbered chains have low and high electrical conduction, respectively. We also noted a dependence of current with the wire size. We study this unexpected behavior using a combination of first principles calculations and simple models based on chemical bond theory. From our studies, the electrons of carbon nanowires present a quasi-free electron behavior and this explains qualitatively the high electrical conduction and the bond lengths with unexpected values for the case of odd nanowires. Our study also allows the understanding of the electric conduction dependence with the number of atoms and their parity in the chain. In the case of odd number chains a proposed π-bond (MpB) model describes unsaturated carbons that introduce a mobile π-bond that changes dramatically the structure and transport properties of these wires. Our results indicate that the nature of bonds plays the main role in the oscillation of quantum electrical conduction for chains with even and odd number of atoms and also that nanowires bonded to graphene nanoribbons behave as a quasi-free electron system, suggesting that this behavior is general and it could also remain if the chains are bonded to other materials.

  14. Bond length and electric current oscillation of long linear carbon chains: Density functional theory, MpB model, and quantum spin transport studies

    Energy Technology Data Exchange (ETDEWEB)

    Oeiras, R. Y.; Silva, E. Z. da [Institute of Physics “Gleb Wataghin”, University of Campinas-Unicamp, 13083-859 Campinas, SP (Brazil)

    2014-04-07

    Carbon linear atomic chains attached to graphene have experimentally been produced. Motivated by these results, we study the nature of the carbon bonds in these nanowires and how it affects their electrical properties. In the present study we investigate chains with different numbers of atoms and we observe that nanowires with odd number of atoms present a distinct behavior than the ones with even numbers. Using graphene nanoribbons as leads, we identify differences in the quantum transport of the chains with the consequence that even and odd numbered chains have low and high electrical conduction, respectively. We also noted a dependence of current with the wire size. We study this unexpected behavior using a combination of first principles calculations and simple models based on chemical bond theory. From our studies, the electrons of carbon nanowires present a quasi-free electron behavior and this explains qualitatively the high electrical conduction and the bond lengths with unexpected values for the case of odd nanowires. Our study also allows the understanding of the electric conduction dependence with the number of atoms and their parity in the chain. In the case of odd number chains a proposed π-bond (MpB) model describes unsaturated carbons that introduce a mobile π-bond that changes dramatically the structure and transport properties of these wires. Our results indicate that the nature of bonds plays the main role in the oscillation of quantum electrical conduction for chains with even and odd number of atoms and also that nanowires bonded to graphene nanoribbons behave as a quasi-free electron system, suggesting that this behavior is general and it could also remain if the chains are bonded to other materials.

  15. H-bond length dependence of the distortion in acid tetrahedron groups H nAsO 4 ( n=1-3)

    Science.gov (United States)

    Ichikawa, Mizuhiko

    1988-07-01

    The H-bond length O⋯O dependence of the distortions of the AsO 4 tetrahedra of acid arsenate groups H nAsO 4 ( n=1-3) have been studied by examining the correlations of the As sbnd O bond lengths, OAsO angles, O sbnd O lengths and Baur's distortion indices (DI) with O⋯O and comparing them with those of the corresponding H nPO 4 groups previously reported. The behavior of the O⋯O dependence of the AsO 4 distortion is analogous to that of PO 4 distortion as a whole, that is (a) all DI increase with increasing O⋯O, and correspondingly some of the individual or average As sbnd O lengths, OAsO angles and O sbnd O lengths correlate with O⋯O consistently; (b) the overall mean values of As sbnd O, OAsO and O sbnd O are reasonably constant in each H nAsO 4 type, most notably in the case of OAsO. The dependence of the PO 4 distortion on O⋯O can be described approximately by a model in which the P atom shifts away from the centroid of the regular tetrahedral framework, but the O⋯O dependence of the AsO 4 distortion is more complicated.

  16. The Repeated Computation of the Bond Length and Ground- State Energy for H2 +%H2+键长和基态能量的再计算

    Institute of Scientific and Technical Information of China (English)

    李旭; 胡先权

    2002-01-01

    Ritz variation method was used to find the numerical relation bctween the energy near the ground - state of the hydrogenmolecular ion H2 + .and the changes of the variation parameter andthe bond length, the computation formula of bond length and ground- state energy for H2 * was also obtained by means of the method ofparabolie interpolation. The computation results were much closer toexperinental values than those of Refs. [ 1,2]' s.%用Ritz变分法求出了氢分子离子H2+基态能量附近的能量随变分参数和分子键长变化的数值关系,并用抛物线插值法获得了H2+键长和基态能量的值及其计算公式,比文献[1,2]更接近于实验值.

  17. Effects of Fe-Fe bond length change in NaZn13-type intermetallic compounds on magnetic properties and magnetic entropy change

    Institute of Scientific and Technical Information of China (English)

    Wang Guang-Jun; Hu Feng-Xia; Wang Fang; Shen Bao-Gen

    2004-01-01

    In this paper the effects of Fe-Fe bond length change on magnetic properties and magnetic entropy change have been investigated on LaFe12.4-xSixCo0.6 and LaFe12.3-xAlxCo0.7 intermetallic compounds. According to the analyses of Fe-Fe bond length change, the variation of Curie temperature and the unusual magnetic phase transition which results in the large magnetic entropy change were explained. The effects of the substitution of Co and Si for Fe on magnetic entropy change and field-induced itinerant-electron metamagnetic transition in LaFe12.4-xSixCo0.6 compounds were also studied and the considerable magnetic entropy change has been achieved.

  18. Correlation of Dative Bond Length and Donor Proton Affinity in Adducts of SO 3: A Good Predictor for HCCCN-SO 3

    Science.gov (United States)

    Hunt, S. W.; Fiacco, D. L.; Craddock, M.; Leopold, K. R.

    2002-04-01

    The rotational spectrum of HCCCN-SO3 has been observed using Fourier transform microwave spectroscopy. The vibrationally averaged structure is that of a symmetric top, with the HCCCN axis along the C3 axis of the SO3, and the nitrogen end near the sulfur. The N-S bond length is 2.567(13) Å, which is slightly shorter than the sum of the van der Waals radii. The NSO angle is 91.7(4)°, indicating a small but distinct distortion of the SO3 from planarity, and the N-S interaction can be described as a chemical bond in an early stage of its formation. The N-S bond lengths in a series of SO3 adducts with amines, nitriles, and pyridine are shown to correlate well with the proton affinities of the bases. In addition, for the bases considered here, the proton affinities vary in a regular manner with the ionization energies corresponding to removal of a lone pair electron. Thus, the trend in proton affinities follows the variation in energy gap between donor and acceptor orbitals in these complexes, accounting for the utility of the proton affinity in correlating aspects of structure and bonding across the series.

  19. Electronic structure and bond length dependence of the effective valence shell Hamiltonian of S2 as studied by quasidegenerate many-body perturbation theory

    Science.gov (United States)

    Wang, Xiao-Chuan; Freed, Karl F.

    1987-03-01

    The effective valence shell Hamiltonian (Hv) of S2 is calculated as a function of internuclear distance using quasidegenerate many-body perturbation theory with the full valence space spanned by eight valence orbitals. Calculated potential curves and excitation energies for several valence states are in good agreement with experiment and are compared with configuration interaction calculations using the same primitive basis. In order to test assumptions of semiempirical theories, we also perform a more approximate calculation of Hv in which the valence space is constructed as the union of the atomic valence spaces with the atomic orbitals taken from atomic SCF calculations. A new and important feature of this approximate, correlated Hv is the use of optimized valence and excited orbitals as determined from a constrained SCF procedure. The matrix elements of this approximate, correlated Hv are transformed to the original nonorthogonal atomic valence basis, and their bond length dependences are fit with simple analytical functions. Some calculated Hv matrix elements agree with the forms commonly postulated for semiempirical integrals, while others display quite different behavior. An example of the latter are the one-center, two-electron integrals which depend significantly on bond length in marked contrast to semiempirical theories which assume them to be bond length independent.

  20. 氢键复合物中键长变化与振动频率移动相关性重访%Correlation between Bond-Length Change and Vibrational Frequency Shift in Hydrogen-Bonded Complexes Revisited

    Institute of Scientific and Technical Information of China (English)

    张愚; 马宁; 王伟周

    2012-01-01

    X—H…Y(Y为电子供体)型氢键形成时,X-H键长伸长或缩短与相应的X-H伸缩振动频率红移或蓝移存在较强的相关性,这也是氢键光谱检测和研究的基础.但是,最近的理论研究却推翻了这一观点,认为X-H键长变化和相应的X-H伸缩振动频率移动在有些氢键体系中并不存在相关性(McDowell,S.A.C.;Buckingham,A.D.J.Am.Chem.Soc.2005,127,15515.).本文中,我们采用更为可信的计算方法,对这一问题进行再研究.结果表明是错误的计算方法导致了McDowell和Buckingham得出错误的结论.在McDowell和Buckingham所研究的氢键体系中,X-H键长变化和相应的X-H伸缩振动频率移动仍存在较强的相关性.%The correlation between the X-H bond-length change and the corresponding X-H stretching frequency shift upon X - H … Y (Y is an electron donor) hydrogen bond formation is the basis for the spectroscopic detection and investigation of the hydrogen bond.However,this view has been questioned in a recent report,suggesting that the widely accepted correlation between the bond-length change and the frequency shift in hydrogen-bonded complexes is unreliable (McDowell,S.A.C.; Buckingham,A.D.J.Am.Chem.Soc.2005,127,15515.).In this work,several robust computational methods have been used to investigate this issue.The results clearly show that a computational artifact leads to the conclusion incorrectly reported by McDowell and Buckingham and that the correlation between the X- H bond-length change and the corresponding X- H stretching frequency shift is still very good in the hydrogen-bonded complexes studied.

  1. Relation between bond-length alternation and two-photon absorption of a push pull conjugated molecules: a quantum-chemical study

    Science.gov (United States)

    Bartkowiak, W.; Zaleśny, R.; Leszczynski, J.

    2003-02-01

    The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ( δ) of a series of prototypical π-conjugated push-pull molecules are presented. The calculations of δ for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ( β and γ) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of δ on the BLA parameter was noticed.

  2. Relation between bond-length alternation and two-photon absorption of a push-pull conjugated molecules: a quantum-chemical study

    Energy Technology Data Exchange (ETDEWEB)

    Bartkowiak, W.; Zalesny, R.; Leszczynski, J

    2003-02-01

    The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ({delta}) of a series of prototypical {pi}-conjugated push-pull molecules are presented. The calculations of {delta} for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ({beta} and {gamma}) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of {delta} on the BLA parameter was noticed.

  3. Heme carbonyls: environmental effects on nu(C-O) and Fe-C/C-O bond length correlations.

    Science.gov (United States)

    Silvernail, Nathan J; Roth, Arne; Schulz, Charles E; Noll, Bruce C; Scheidt, W Robert

    2005-10-19

    The synthesis and characterization of four low-spin (carbonyl)iron(II) tetraphenylporphyrinates, [Fe(TPP)(CO)(L)], where L = 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole (unsolvated), and 1,2-dimethylimidazole (toluene solvate) are reported. The complexes show nearly the same value of nu(C-O) in toluene solution (1969-72 cm(-1)) but a large range of CO stretching frequencies in the solid-state (1926-1968 cm(-1)). The large solid-state variation results from CO interactions in the solid state, as shown by an examination of the crystal structures of the four complexes. The high precision of the four structures obtained allows us to make a number of structural and spectroscopic correlations that describe the Fe-C-O and N(Im)-Fe-CO units. The values of nu(C-O) and the Fe-C and C-O bond distances are strongly correlated and provide a structural, as well as a spectroscopic, correlation of the pi back-bonding model. The interactions of CO described are closely related to the large range of CO stretching frequencies observed in heme proteins and specific interactions observed in carbonylmyoglobin (MbCO).

  4. Geometry and bond-length alternation in nonlinear optical materials. II. Effects of donor strength in two push-pull molecules.

    Science.gov (United States)

    Gainsford, Graeme J; Bhuiyan, M Delower H; Kay, Andrew J

    2008-04-01

    The compounds N-[2-(4-cyano-5-dicyanomethylene-2,2-dimethyl-2,5-dihydrofuran-3-yl)vinyl]-N-phenylacetamide, C(20)H(16)N(4)O(2), (I), and 2-{3-cyano-5,5-dimethyl-4-[2-(piperidin-1-yl)vinyl]-2,5-dihydrofuran-2-ylidene}malononitrile 0.376-hydrate, C(17)H(18)N(4)O x 0.376 H(2)O, (II), are novel push-pull molecules. The significant bonding changes in the polyene chain compared with the parent molecule 2-dicyanomethylene-4,5,5-trimethyl-2,5-dihyrofuran-3-carbonitrile are consistent with the relative electron-donating properties of the acetanilido and piperidine groups. The packing of (I) utilizes one phenyl-cyano C-H...N and two phenyl-carbonyl C-H...O hydrogen bonds. Compound (II) crystallizes with a partial water molecule (0.376H(2)O), consistent with cell packing that is dominated by attractive C-H...N(cyano) interactions. These compounds are precursors to novel nonlinear optical chromophores, studied to assess the impact of donor strength and the extent of conjugation on bond-length alternation, crystal packing and aggregation.

  5. 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.

    Science.gov (United States)

    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

  6. Safe-by-Design CuO Nanoparticles via Fe-Doping, Cu-O Bond Length Variation, and Biological Assessment in Cells and Zebrafish Embryos.

    Science.gov (United States)

    Naatz, Hendrik; Lin, Sijie; Li, Ruibin; Jiang, Wen; Ji, Zhaoxia; Chang, Chong Hyun; Köser, Jan; Thöming, Jorg; Xia, Tian; Nel, Andre E; Mädler, Lutz; Pokhrel, Suman

    2017-01-24

    The safe implementation of nanotechnology requires nanomaterial hazard assessment in accordance with the material physicochemical properties that trigger the injury response at the nano/bio interface. Since CuO nanoparticles (NPs) are widely used industrially and their dissolution properties play a major role in hazard potential, we hypothesized that tighter bonding of Cu to Fe by particle doping could constitute a safer-by-design approach through decreased dissolution. Accordingly, we designed a combinatorial library in which CuO was doped with 1-10% Fe in a flame spray pyrolysis reactor. The morphology and structural properties were determined by XRD, BET, Raman spectroscopy, HRTEM, EFTEM, and EELS, which demonstrated a significant reduction in the apical Cu-O bond length while simultaneously increasing the planar bond length (Jahn-Teller distortion). Hazard screening was performed in tissue culture cell lines and zebrafish embryos to discern the change in the hazardous effects of doped vs nondoped particles. This demonstrated that with increased levels of doping there was a progressive decrease in cytotoxicity in BEAS-2B and THP-1 cells, as well as an incremental decrease in the rate of hatching interference in zebrafish embryos. The dissolution profiles were determined and the surface reactions taking place in Holtfreter's solution were validated using cyclic voltammetry measurements to demonstrate that the Cu(+)/Cu(2+) and Fe(2+)/Fe(3+) redox species play a major role in the dissolution process of pure and Fe-doped CuO. Altogether, a safe-by-design strategy was implemented for the toxic CuO particles via Fe doping and has been demonstrated for their safe use in the environment.

  7. The d3/d2 alkyne complexes [MX2(eta-RC[triple bond, length as m-dash]CR)Tp']z (X = halide, z = 0 and 1+): final links in a d6-d2 redox family tree.

    Science.gov (United States)

    Adams, Christopher J; Anderson, Kirsty M; Connelly, Neil G; Harding, David J; Hayward, Owen D; Orpen, A Guy; Patrón, Elena; Rieger, Philip H

    2009-01-21

    The d4 halide complexes [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp'] [R = Me, M = W, X = F; R = Ph, M = Mo or W, X = F or Cl; Tp' = hydrotris(3,5-dimethylpyrazolyl)borate] undergo two-electron oxidation in the presence of a halide source to give the d2 monocations [MX1X2(eta-PhC[triple bond, length as m-dash]CPh)Tp']+ (R = Me, M = W, X1 = X2 = F; R = Ph, M = Mo, X1 = X2 = F or Cl; M = W, X1 = X2 = F or Cl; X1 = F, X2 = Cl). Each monocation (R = Ph) shows two reversible one-electron reductions (the second process was not detected for R = Me) corresponding to the stepwise formation of the neutral d3 and monoanionic d4 analogues, [MX1X2(eta-PhC[triple bond, length as m-dash]CPh)Tp'] and [MX1X2(eta-PhC[triple bond, length as m-dash]CPh)Tp']- respectively; the potentials for the two processes can be 'tuned' over a range of ca. 1.0 V by varying M and X. Chemical one-electron reduction of [MX2(eta-PhC[triple bond, length as m-dash]CPh)Tp']+ gave [MX2(eta-PhC[triple bond, length as m-dash]CPh)Tp'] (M = Mo or W, X = F or Cl). X-Ray structural studies on the redox pairs [WX2(eta-PhC[triple bond, length as m-dash]CPh)Tp']z (X = F and Cl, z = 0 and 1+) show the alkyne to bisect the X-W-X angle in the d2 cations but align more closely with one M-X bond in the neutral d3 molecules, consistent with the anisotropic ESR spectra of the latter; the solution ESR spectrum of [MoF2(eta-PhC[triple bond, length as m-dash]CPh)Tp'] showed equivalent fluorine atoms, i.e the alkyne oscillates at room temperature. The successful isolation of [MX2(eta-PhC[triple bond, length as m-dash]CPh)Tp']+ and [MX2(eta-PhC[triple bond, length as m-dash]CPh)Tp'] completes a series in which d6 to d2 alkyne complexes are linked in a redox family tree by sequential one-electron transfer and substitution reactions. The implications for such trees in the production of new species and the selective synthesis of paramagnetic complexes acting as synthetically useful 'alkyne radicals' are discussed.

  8. Vapour pressure of components made by the presence of HgS(s,alpha) in an oil/gas reservoir and consequences for the produced gas

    Energy Technology Data Exchange (ETDEWEB)

    Oestvold, T.; Gustavsen, Oe.; Grande, K.; Aas, N.; Olsvik, Mimmi Kjetsaa

    2006-03-15

    A thermodynamic analysis is presented on how components made from HgS (s,alpha), existing in a oil/gas reservoir, will distribute themselves between gas, water, liquid and solid components as a function of temperature and pressure. The consequence of the formation of mercury containing components on gas injection and on gas quality is discussed. Since equilibrium is established in the model calculation, other gas components in the gas phase and components in condensed phases present will also influence the composition of the gas. Six cases are considered in the calculation: 1) HgS(s,alpha) - Ar(g), 2) HgS(s,alpha) - Ar (g) - water with 10-4 molal NaCl at pH = 7, 3) HgS(s,alpha) - CH{sub 4}(g), 4) HgS(s,alpha) - CH{sub 4} (g) - water with 10-4 molal NaCl at pH = 7 and 5) HgS(s,alpha) - natural gas - water with 10-4 molal NaCl at pH = 7, 6) HgS(s,alpha) - natural gas - water with 10-4 molal NaCl and 5*10-5 molal NO-3- at pH = 7. When HgS(s,alpha) is present in an oil reservoir at 170 deg C and 200 bar, these calculations show that the major components formed are: H{sub 2}(g), H{sub 2}S(g), Hg(l) and Hg(g) together with carbon. Mercury in the gas phase in the cases 1) is 4*10-7 bar and is determined by the evaporation and decomposition HgS(g) in the reservoir. In case 2) P{sub Hg} = 5.7*10-4 bar mainly determined by the formation of sulphate in the water phase. In the cases 3), 4) and 5) these calculations show that the major components formed are: H{sub 2}(g), H{sub 2}S(g), Hg(l) and Hg(g) together with carbon, and the gas phase is dominated by Hg(g) at approx. *10-3 bar. The water phase may contain Hg(CH{sub 3}NH{sub 2}){sub 2}2+ if NO{sub 3}- for some reasons is introduced into the formation water, and the very carcinogenic dimethyl mercury compound, C{sub 2}HgH{sub 6}, can be formed in the gas phase. Both compounds, however, in insignificant low concentration/partial pressure. (Author)

  9. Zuotai and HgS differ from HgCl2 and methyl mercury in Hg accumulation and toxicity in weanling and aged rats.

    Science.gov (United States)

    Zhang, Bin-Bin; Li, Wen-Kai; Hou, Wei-Yu; Luo, Ya; Shi, Jing-Zhen; Li, Cen; Wei, Li-Xin; Liu, Jie

    2017-09-15

    Mercury sulfides are used in Ayurvedic medicines, Tibetan medicines, and Chinese medicines for thousands of years and are still used today. Cinnabar (α-HgS) and metacinnabar (β-HgS) are different from mercury chloride (HgCl2) and methylmercury (MeHg) in their disposition and toxicity. Whether such scenario applies to weanling and aged animals is not known. To address this question, weanling (21d) and aged (450d) rats were orally given Zuotai (54% β-HgS, 30mg/kg), HgS (α-HgS, 30mg/kg), HgCl2 (34.6mg/kg), or MeHg (MeHgCl, 3.2mg/kg) for 7days. Accumulation of Hg in kidney and liver, and the toxicity-sensitive gene expressions were examined. Animal body weight gain was decreased by HgCl2 and to a lesser extent by MeHg, but unaltered after Zuotai and HgS. HgCl2 and MeHg produced dramatic tissue Hg accumulation, increased kidney (kim-1 and Ngal) and liver (Ho-1) injury-sensitive gene expressions, but such changes are absent or mild after Zuotai and HgS. Aged rats were more susceptible than weanling rats to Hg toxicity. To examine roles of transporters in Hg accumulation, transporter gene expressions were examined. The expression of renal uptake transporters Oat1, Oct2, and Oatp4c1 and hepatic Oatp2 was decreased, while the expression of renal efflux transporter Mrp2, Mrp4 and Mdr1b was increased following HgCl2 and MeHg, but unaffected by Zuotai and HgS. Thus, Zuotai and HgS differ from HgCl2 and MeHg in producing tissue Hg accumulation and toxicity, and aged rats are more susceptible than weanling rats. Transporter expression could be adaptive means to reduce tissue Hg burden. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. DOPING AND BOND LENGTH CONTRIBUTIONS TO Mn K-EDGE SHIFT IN La1-xSrxMnO3 AND THEIR CORRELATION WITH ELECTRICAL TRANSPORT BEHAVIOUR.

    Energy Technology Data Exchange (ETDEWEB)

    PANDEY,S.K.; KHALID,S.; BINDU, R.; KUMAR, A.; PIMPALE, A.V.

    2006-12-04

    The experimental Mn K-edge x-ray absorption spectra of La{sub 1-x}Sr{sub x}MnO{sub 3}, x = 0 - 0.7 are compared with the band structure calculations using spin polarized density functional theory. It is explicitly shown that there is a correspondence between the inflection point on the absorption edge and the center of gravity of the unoccupied Mn 4p-band. This correspondence has been used to separate the doping and size contributions to edge shift due to variation in number of electrons in valence band and Mn-O bond lengths, respectively when Sr is doped into LaMnO{sub 3}. Such separation is helpful to find the localization behavior of charge carriers and to understand the observed transport properties and type of charge carrier participating in the conduction process in these compounds.

  11. Structures and bonding on a colloidal silver surface of the various length carboxyl terminal fragments of bombesin.

    Science.gov (United States)

    Podstawka, Edyta; Ozaki, Yukihiro; Proniewicz, Leonard M

    2008-10-07

    Raman (RS) and surface-enhanced Raman scattering spectra (SERS) were measured for various length carboxyl terminal fragments (X-14 of amino acid sequence) of bombesin ( BN): BN13-14, BN12-14, BN11-14, BN10-14, BN9-14, and BN8-14 in silver colloidal solutions. Density functional theory (DFT) calculations of Raman wavenumbers and intensities with extended basis sets (B3LYP/6-31++G**) were performed with the aim of providing the definitive band allocations to the normal coordinates. The proposed band assignment is consistent with the assignment for similar compounds reported in the literature. The nonadsorbed and adsorbed molecular structures were deducted by detailed spectral analysis of the RS and SERS spectra, respectively. This analysis also allowed us to propose the particular surface geometry and orientation of these peptides on silver surface, and their specific interaction with the surface. For example, a SERS spectrum of BN8-14 indicates that the interaction of a thioether atom and Trp8 with the silver surface is favorable and may dictate the orientation and conformation of adsorbed peptide. One of the most prominent and common features in all of the fragments' SERS spectra is a approximately 692 cm (-1) band due to nu(C-S) accompanied by two or three bands of different C-S conformers for all, except BN8-14, which suggests that all of the above-mentioned compounds adsorb on the silver surface through the thioether atom and that the attachment of Trp8 produces limitation in a number of possible C-S conformers adopted on this surface. Our results also show clearly that His12 and CO do not interact with the colloid surface, which supports our earlier results.

  12. Formation of Methyl Mercury During Restoration of Forested Wetlands in Relation to Hg, S and Fe Geochemistry

    Science.gov (United States)

    Fredriksson, I.; Skyllberg, U.

    2007-12-01

    In 1999 the Swedish Parliament adopted fifteen National Environmental Quality Objectives (NEQO), one of these is the objective of "Thriving wetlands" with thee goal to restore 12 000 ha of wetlands until 2010. Given the current knowledge about methyl mercury (MeHg) production in wetlands, and subsequent bioaccumulation, the objective of thriving wetlands may be in conflict with other NEQO. In this project wetland restoration objects in different environmental settings (differing in primary productivity, climate and sulfur and iron geochemistry) are selected. After a pre-treatment period of 1-2 years, wetlands will be restored by increasing the ground water table. Methylation and demethylation rates, determined in incubation experiments using stable isotopes, will be linked to the chemical speciation of Hg, S and Fe in soil and soil solution using techniques like sulfur and iron X-ray absorption near edge spectroscopy (XANES) and Hg extended x-ray absorption fine structure (EXAFS) spectroscopy. This is done both prior to and during the restoration. Because of the strong link between Fe(II) and S(-II) geochemistry we hypothesize that net MeHg production is limited by the availability of dissolved, neutral Hg-sulfides in iron-rich environments. Preliminary data prior to restoration indeed indicate that besides primary productivity, the availability of neutral Hg-sulfides in the pore water of soils is important for the net production of MeHg.

  13. Target-stimulated metallic HgS nanostructures on a DNA-based polyion complex membrane for highly efficient impedimetric detection of dissolved hydrogen sulfide.

    Science.gov (United States)

    Zhuang, Junyang; Fu, Libing; Lai, Wenqiang; Tang, Dianping; Chen, Guonan

    2013-12-11

    Target-stimulated metallic HgS nanostructures formed on the DNA-based polyion complex (PIC) membrane were for the first time utilized as an efficient scheme for impedimetric detection of hydrogen sulfide (H2S) by coupling insoluble precipitation with sensitivity enhancement.

  14. Exposure to Low Dose of Cinnabar (a Naturally Occurring Mercuric Sulfide (HgS Caused Neurotoxicological Effects in Offspring Mice

    Directory of Open Access Journals (Sweden)

    Chun-Fa Huang

    2012-01-01

    Full Text Available Cinnabar, a naturally occurring mercuric sulfide (HgS, has long been used in Chinese mineral medicine for more than 2000 years. Although mercury is well-known for its toxicity, whether cinnabar induces neurotoxicity, especially in infants and children, is unknown. The purpose of this study was to explore the neurotoxic effects of low-dose of cinnabar (10 mg/kg/day on developing mice. The results revealed neurobehavioral defects in F1-C-Cin group, which were associated with Hg accumulation, increased NOx levels in whole blood, and Na+/K+-ATPase activities in brain tissues. F1- and F2-Cin-V groups were found to increase brain Hg contents and prominent neurobehavioral defects compared with F1-C-V group, suggesting that the fetal brain was more susceptible to irreversible effects for cinnabar-induced damage. Moreover, F1- and F2-Cin-Cin groups had severely neurobehavioral dysfunctions, closely correlated with the further alteration of NOx levels and Na+/K+-ATPase activities than F1- and F2-C-Cin groups. Effects in F2-Cin-Cin group were more significant than those in F1-Cin-Cin group. In conclusion, this study demonstrates that exposure to low-dose of cinnabar during the perinatal and developmental stages results in irreversible and severe injuries of the neurotoxicity in offspring, and NOx and Na+/K+-ATPase activities may exist potential and useful biomarkers for neurotoxicity-induced by low-doses of mercuric compounds.

  15. Bond length alternation in heptalene

    NARCIS (Netherlands)

    Boer-Veenendaal, P.C. den; Vliegenthart, J.A.; Boer, D.H.W. den

    1962-01-01

    Using LCAO-MO theory it is shown that the heptalene molecule possesses only a centre of symmetry instead of two mutually perpendicular twofold axes in the molecular plane. Charges and free valence numbers indicate that the 1-position should be the most reactive.

  16. Effect of self-interaction error in the evaluation of the bond length alternation in trans-polyacetylene using density-functional theory

    Science.gov (United States)

    Ciofini, I.; Adamo, C.; Chermette, H.

    2005-09-01

    The calculation of the bond-length alternation (BLA) in trans-polyacetylene has been chosen as benchmark to emphasize the effect of the self-interaction error within density-functional theory (DFT). In particular, the BLA of increasingly long acetylene oligomers has been computed using the Møller-Plesset wave-function method truncated at the second order and several DFT models. While local-density approximation (LDA) or generalized gradient corrected (GGA) functionals strongly underestimate the BLA, approaches including self-interaction corrections (SIC) provide significant improvements. Indeed, the simple averaged-density SIC scheme (ADSIC), recently proposed by Legrand et al. [J. Phys. B 35, 1115 (2002)], provides better results for the structure of large oligomers than the more complex approach of Krieger et al. [Phys. Rev. A 45, 101 (1992)]. The ADSIC method is particularly promising since both the exchange-correlation energy and potential are improved with respect to standard LDA/GGA using a physically appealing correction, through a different route than the more popular approach through the Hartree-Fock exchange inclusion within the hybrid functionals.

  17. The origin of unequal bond lengths in the $\\mathrm{\\tilde{C}}$ $^1$B$_2$ state of SO$_2$: Signatures of high-lying potential energy surface crossings in the low-lying vibrational structure

    CERN Document Server

    Park, G Barratt; Field, Robert W

    2016-01-01

    The $\\mathrm{\\tilde{C}}$ $^1$B$_2$ state of SO$_2$ has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. The asymmetry in the potential energy surface is expressed as a staggering in the energy levels of the $\

  18. ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

    Directory of Open Access Journals (Sweden)

    Peter A. Ajibade

    2011-08-01

    Full Text Available The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm, 2.91 eV (426 nm and 4.27 eV (290 nm for the ZnS, CdS and HgS samples respectively.

  19. Polarized and depolarized Raman spectra of liquid carbon disulfide in the pressure range 0-10 kbar. I. Vibration frequencies, C-S bond length, and Fermi resonance

    Science.gov (United States)

    Ikawa, S.; Whalley, Edward

    1986-09-01

    The effect of pressure on the polarized and depolarized Raman spectra of liquid carbon disulphide, i.e., the peak frequencies, bandwidths, and relative intensities of both the allowed ν1 and 2ν2 bands and the interaction-induced ν2 and ν3 bands, have been measured at 22 °C up to 10 kbar. This paper discusses the effect of pressure on the frequencies and on the relative isotropic intensity of the ν1 and 2ν2 bands. The frequency of the ν1 band increases linearly with pressure, within the experimental uncertainty, at the rate 0.16±0.01 cm-1 kbar-1, and the frequencies of the ν2, ν3, and 2ν2 bands decrease nonlinearly. The frequency shifts are described by second-order perturbation theory with the molecular anharmonicity and the intermolecular interaction as perturbations. The leading terms of the shifts consist of the same derivative of the interaction potential, multiplied by different anharmonicity constants, and the shifts of the ν1 and 2ν2 bands suggests that the C-S bond length decreases at the rate 2×10-4 Å kbar-1. The relative isotropic intensity of the 2ν2 and ν1 bands increases with pressure at the rate 0.050 kbar-1, whereas the anisotropic 2ν2 intensity relative to the isotropic ν1 intensity is independent of pressure to the experimental precision of ˜0.005. The effect of pressure on the second derivative of the isotropic and anisotropic parts of the polarizability with respect to the bend coordinate was estimated as 1.1×10-43 C m2 V-1 kbar-1 and ˜0, respectively, from these values.

  20. Polysulfide anions II: structure and vibrational spectra of the S4(2-) and S5(2-) anions. Influence of the cations on bond length, valence, and torsion angle.

    Science.gov (United States)

    el Jaroudi, O; Picquenard, E; Demortier, A; Lelieur, J P; Corset, J

    2000-06-12

    The influence of the cations on bond length, valence, and torsion angle of S4(2-) and S5(2-) anions was examined in a series of solid alkali tetra- and pentasulfides by relating their Raman spectra to their known X-ray structures through a force-field analysis. The IR and Raman spectra of BaS4.H2O and the Raman spectra of (NH4)2S4.nNH3, gamma-Na2S4, and delta-Na2S5 are presented. The similarity of spectra of gamma-Na2S4 with those of BaS4.H2O suggests similar structures of the S4(2-) anions in these two compounds with a torsion angle smaller than 90 degrees. The variations of SS bond length, SSS valence angle, and dihedral angle of Sn2- anions are related to the polarization of the lone pair and electronic charge of the anion by the electric field of the cations. A correlation between the torsion angle and the SSS valence angle is shown as that previously reported between the length of the bond around which the torsion takes place and the dihedral angle value. These geometry changes are explained by the hyperconjugation concept and the electron long-pair repulsion.

  1. Ultrafast laser control of vibrational dynamics for a two-dimensional model of HONO 2 in the ground electronic state: separation of conformers, control of the bond length, selective preparation of the discrete and the continuum states

    Science.gov (United States)

    Oppel, M.; Paramonov, G. K.

    1998-06-01

    Selective excitation of the vibrational bound and the continuum states, controlled by subpicosecond infrared (IR) laser pulses, is simulated within the Schrödinger wave function formalism for a two-dimensional model of the HONO 2 molecule in the ground electronic state. State-selective excitation of the OH bond is achieved by single optimal laser pulses, with the probability being 97% for the bound states and more than 91% for the resonances. Stable, long-living continuum states are prepared with more than 96% probability by two optimal laser pulses, with the expectation energy of the molecule being well above the dissociation threshold of the ON single bond, and its life-time being at least 100 ps. The length of the ON single bond can be controlled selectively: stretching and contraction by about 45% of its equilibrium length are demonstrated. Laser separation of spatial conformers of HONO 2 in inhomogeneous conditions occurring on an anisotropic surface or created by a direct current (DC) electric field is analysed. The relative yields of target conformers may be very high, ranging from 10 to 10 8, and the absolute yields of up to 40% and more are calculated.

  2. Analysis of the vibronic structure of the trans-stilbene fluorescence and excitation spectra: the S0 and S1 PES along the Ce[double bond, length as m-dash]Ce and Ce-Cph torsions.

    Science.gov (United States)

    Orlandi, Giorgio; Garavelli, Marco; Zerbetto, Francesco

    2017-09-20

    We analyze the highly resolved vibronic structure of the low energy (≤200 cm(-1)) region of the fluorescence and fluorescence excitation spectra of trans-stilbene in supersonic beams. In this spectral region the vibronic structure is associated mainly with vibrational levels of the Ce-Ce torsion (τ) and the au combination of the two Ce-Cph bond twisting (ϕ). We base this analysis on the well-established S0(τ, ϕ) two-dimensional potential energy surface (PES) and on a newly refined S1(τ, ϕ) PES. We obtain vibrational eigenvalues and eigenvectors of the anharmonic S0(τ, ϕ) and S1(τ, ϕ) PES using a numerical procedure based on the Meyer's flexible model [R. Meyer, J. Mol. Spectrosc., 1979, 76, 266]. Then we derive Franck-Condon factors and therefore intensities of the relevant vibronic bands for the S0 → S1 excitation and S1 → S0 fluorescence spectra. Furthermore, we assess the role of the bg combination of the two Ce-Cph bond twisting (ν48) in the structure of the S1 → S0 fluorescence spectra. By the use of these results we are able to assign most of the low energy vibrational levels of the S0 → S1 excitation spectra and of the fluorescence spectra of the emission from several low energy S1 vibronic levels. The good agreement between the observed and the computed vibrational structure of the S0 → S1 and S1 → S0 spectra suggests that the proposed picture of the E1(τ, ϕ) and E0(τ, ϕ) PES, in particular along the coordinate τ governing trans-cis photo-isomerization in S1, is accurate. In S0, the barriers for the Ce[double bond, length as m-dash]Ce torsion and for the au type Ce-Cph bond twisting are 16 080 cm(-1) and 3125 cm(-1), respectively, while in S1, where the bond orders of the Ce[double bond, length as m-dash]Ce and Ce-Cph bonds are reversed, the two barriers become 1350 cm(-1) and 8780 cm(-1), respectively.

  3. Engineering a disulfide bond in the lid hinge region of Rhizopus chinensis lipase: increased thermostability and altered acyl chain length specificity.

    Directory of Open Access Journals (Sweden)

    Xiao-Wei Yu

    Full Text Available The key to enzyme function is the maintenance of an appropriate balance between molecular stability and structural flexibility. The lid domain which is very important for "interfacial activation" is the most flexible part in the lipase structure. In this work, rational design was applied to explore the relationship between lid rigidity and lipase activity by introducing a disulfide bond in the hinge region of the lid, in the hope of improving the thermostability of R. chinensis lipase through stabilization of the lid domain without interfering with its catalytic performance. A disulfide bridge between F95C and F214C was introduced into the lipase from R. chinensis in the hinge region of the lid according to the prediction of the "Disulfide by Design" algorithm. The disulfide variant showed substantially improved thermostability with an eleven-fold increase in the t(1/2 value at 60°C and a 7°C increase of T(m compared with the parent enzyme, probably contributed by the stabilization of the geometric structure of the lid region. The additional disulfide bond did not interfere with the catalytic rate (k(cat and the catalytic efficiency towards the short-chain fatty acid substrate, however, the catalytic efficiency of the disulfide variant towards pNPP decreased by 1.5-fold probably due to the block of the hydrophobic substrate channel by the disulfide bond. Furthermore, in the synthesis of fatty acid methyl esters, the maximum conversion rate by RCLCYS reached 95% which was 9% higher than that by RCL. This is the first report on improving the thermostability of the lipase from R. chinensis by introduction of a disulfide bond in the lid hinge region without compromising the catalytic rate.

  4. (2S,4R)-4-hydroxyproline(4-nitrobenzoate): strong induction of stereoelectronic effects via a readily synthesized proline derivative. Crystallographic observation of a correlation between torsion angle and bond length in a hyperconjugative interaction.

    Science.gov (United States)

    Pandey, Anil K; Yap, Glenn P A; Zondlo, Neal J

    2014-05-01

    (2S,4R)-4-Hydroxyproline(4-nitrobenzoate) was synthesized. The crystal structure revealed an exo ring pucker, with the nitrobenzoate pseudoaxial on the pyrrolidine envelope and antiperiplanar to C(β) and C(δ) C-H bonds. The unit cell exhibited variation in C(δ)-H/C(γ)-O and C(β)-H/C(γ)-O torsion angles, with a 15° increase in torsion angle (148° to 163°) observed to result in a 0.018 Å decrease in C(δ)-H/C(γ)-O bond length, consistent with favorable σC-H → σ*C-O hyperconjugative interactions increasing with greater orbital overlap.

  5. 3D, 2D and 1D networks via N-H…O and N-H…N hydrogen bonding by the bis-amide analogues: Effect of chain lengths and odd-even spacers

    Indian Academy of Sciences (India)

    Gargi Mukherjee; Kumar Biradha

    2014-09-01

    The synthesis, crystal structures and hydrogen bonding networks of four members of the bis(pyridinecarboxamido)alkane and bis(pyridyl)alkanediamides series (1 ≤ ≤ 8), where the amide moieties are separated by alkyl chain (-(CH2)-) having even or odd number of -(CH2)-groups are explored and correlated with the previously reported structures. The odd members (n= odd) of both the series are found to adopt three-dimensional networks in contrast to the 1D or 2D structures of the even members (n= even). This odd-even effect on the dimensionality of the networks however disappears with increase in chain length.

  6. On the chalcogenophilicity of mercury: evidence for a strong Hg-Se bond in [Tm(Bu(t))]HgSePh and its relevance to the toxicity of mercury.

    Science.gov (United States)

    Melnick, Jonathan G; Yurkerwich, Kevin; Parkin, Gerard

    2010-01-20

    One of the reasons for the toxic effects of mercury has been attributed to its influence on the biochemical roles of selenium. For this reason, it is important to understand details pertaining to the nature of Hg-Se interactions and this has been achieved by comparison of a series of mercury chalcogenolate complexes that are supported by tris(2-mercapto-1-t-butyl-imidazolyl)hydroborato ligation, namely [Tm(Bu(t))]HgEPh (E = S, Se, Te). In particular, X-ray diffraction studies on [Tm(Bu(t))]HgEPh demonstrate that although the Hg-S bonds involving the [Tm(Bu(t))] ligand are longer than the corresponding Cd-S bonds of [Tm(Bu(t))]CdEPh, the Hg-EPh bonds are actually shorter than the corresponding Cd-EPh bonds, an observation which indicates that the apparent covalent radii of the metals in these compounds are dependent on the nature of the bonds. Furthermore, the difference in Hg-EPh and Cd-EPh bond lengths is a function of the chalcogen and increases in the sequence S (0.010 A) selenolate transfer from zinc to mercury upon treatment of [Tm(Bu(t))]HgSCH(2)C(O)N(H)Ph with [Tm(Bu(t))]ZnSePh. The significant selenophilicity of mercury is in accord with the aforementioned proposal that one reason for the toxicity of mercury is associated with it reducing the bioavailability of selenium.

  7. Doping and bond length contributions to Mn K-edge shift in La1-SrMnO3 (=0-0.7) and their correlation with electrical transport properties

    Indian Academy of Sciences (India)

    S K Pandey; R Bindu; Ashwini Kumar; S Khalid; A V Pimpale

    2008-02-01

    The room temperature experimental Mn K-edge X-ray absorption spectra of La1-SrMnO3 ( = 0-0.7) are compared with the band structure calculations using spin polarized density functional theory. It is explicitly shown that the observed shift in the energy of Mn K-edge on substitution of divalent Sr on trivalent La sites corresponds to the shift in the center of gravity of the unoccupied Mn 4-band contributing to the Mn K-absorption edge region. This correspondence is then used to separate the doping and size contributions to the edge shift due to variation in the number of electrons in valence band and Mn-O bond lengths, respectively, when Sr is doped into LaMnO3. Such separation is helpful to find the localization behaviour of charge carriers and to understand the observed transport properties of these compounds.

  8. The puzzle of bond length variation in substituted cyclobutenes. A new example: molecular structure and conformations of 1,2-dimethoxy-3,3,4,4-tetrafluorocyclobut-1-ene.

    Science.gov (United States)

    Richardson, Alan D; Hedberg, Kenneth; Lunelli, Bruno

    2010-04-29

    The structure and composition of 1,2-dimethoxy-3,3,4,4-tetrafluorocyclobut-1-ene (DMCB) have been measured by electron diffraction from the gas at a temperature of 370 K with the help of auxiliary data from molecular orbital and normal coordinate calculations, the former at several levels of theory and basis-set size, most importantly B3LYP/cc-pVTZ. The compound was found to exist primarily as a rotamer of C(s) symmetry (ca. 98%; 2sigma = 11%) with the remainder one of C(2v) symmetry; theory predicts about 88% C(s). Values for some of the more important parameters (r(g)/A; angle(alpha)/deg) of the C(s) form are r(C=C) = 1.337(21), r(C1-C4) = 1.496(8), r(C2-C3) = 1.501(8), r(C3-C4) = 1.567(12), r(C1-O) = 1.318(12), r(C2-O) = 1.340(12), r(C3-F) = 1.375(4), r(C4-F) = 1.368(4), angle(ave)(C=C-C) = 94.4(4), angle(ave)(C=C-O) = 133.5(12), angle(ave)(C-O-C) = 119.6(13), and angle(ave)(F-C-F) = 104.4(7). Surprisingly, although electron-diffraction values for the fluorinated C3-C4 bond in other cyclobutenes are greater than that for cyclobutene itself, that is not the case for DMCB where it is found to be about the same. Details of the DMCB structure, together with possible reasons for the observed variations in the length of the C3-C4 bond in fluorinated cyclobutene-like molecules, are discussed.

  9. 桩底嵌岩锚杆锚固段应力分布研究%Distribution of Stresses on Bonded Length of Rock-socketed Anchor Rods under Pile Tip

    Institute of Scientific and Technical Information of China (English)

    赵明华; 廖彬彬; 刘思思; 黄利雄

    2011-01-01

    According to the mechanical characteristics of compression type rock-socketed anchor rods under pile toe in the system of vertical load-bearing capacity test of pile foundation by the self-anchored technique,an elastic solution for stress distribution of compression type anchor rods was derived based on the Kelvin's solution of elastic displacement and the dilatancy effect between anchorage body and surrounding rock. Then,the distribution of stresses of rock-socketed anchor rods under pile toe along the anchorage length were analy ed on the basis of the obtained analytical solution, and the effect of various geotechnical parameters on shear stress distribution along bonded length was also analyzed. The results show that ( 1 ) the normal stress along the anchorage length decreases with the distance from the loaded plate increases; (2) the shear stress increases at first and then decreases with the distance from the loaded plate increases, the peak shear stress increases with the angle of dilatancy increases, and decreases with the Poisson's ratio of the anchorage body increases.%针对基桩竖向承载力自锚法测试体系中桩底嵌岩压力型锚杆的受力特点,基于Kelvin问题的弹性位移解,并结合锚固体-岩石作用的剪胀机理,推导了压力型锚杆应力分布的弹性解.基于所获得的解答,分析了桩底嵌岩锚杆锚固段应力沿锚固长度的分布规律,并分析了各种岩土参数变化对锚固段剪应力分布的影响.结果表明:桩底嵌岩锚杆锚固段上的正应力随着距承载板距离的增大而减小,剪应力随着距承载板距离的增大先增大后减小,峰值剪应力随着剪胀角的增大而增大,随着锚固体泊松比的增大而减小.

  10. Flame Length

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Flame length was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  11. Conciliatory Inductive Model Explaining the Origin of Changes in the η(2)-SiH Bond Length Caused by Presence of Strongly Electronegative Atoms X (X = F, Cl) in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] (n = 0-3) Complexes.

    Science.gov (United States)

    Jabłoński, Mirosław

    2016-06-23

    Using three theoretical methods, QTAIM, IQA, and NCI, we analyze an influence of halogen atoms X (X = F, Cl) substituted at various positions in the -SiH3-nXn group on the charge density distribution within the η(2)-SiH bond and on the SiH bond energies in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes and isolated HSiH3-nXn molecules. It is shown that shortening of the η(2)-SiH bond in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes should be considered as a normal inductive result of halogenation. This η(2)-SiH bond's compression may, however, be overcome by a predominant elongation resulting from a contingent presence of a halogen atom at position trans to the η(2)-SiH bond. This trans effect is particularly large for bulky and highly polarizable chlorine. Moreover, peculiar properties of the trans chlorine atom are manifested in several ways. To explain the origin of all the observed changes in both the length and the electron charge distribution of the η(2)-SiH bond in investigated Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes a new model, called the Conciliatory Inductive Model, is being proposed.

  12. Excitation spectra and ground-state properties from density functional theory for the inverted band-structure systems $\\beta$-HgS, HgSe, and HgTe

    CERN Document Server

    Delin, A

    2002-01-01

    We have performed a systematic density-functional study of the mercury chalcogenide compounds $\\beta$-HgS, HgSe, and HgTe using an all-electron full-potential linear muffin-tin orbital (FP-LMTO) method. We find that, in the zinc-blende structure, both HgSe and HgTe are semimetals whereas $\\beta$-HgS has a small spin-orbit induced band gap. Our calculated relativistic photoemission and inverse photoemission spectra (PES and IPES, respectively) reproduce very well the most recently measured spectra, as do also our theoretical optical spectra. In contrast to the normal situation, we find that the local density approximation (LDA) to the density functional gives calculated equilibrium volumes in much better agreement with experiment than does the generalized gradient corrected functional (GGA). We also address the problem of treating relativistic $p$ electrons with methods based on a scalar-relativistic basis set, and show that the effect is rather small for the present systems.

  13. Bond Issues.

    Science.gov (United States)

    Pollack, Rachel H.

    2000-01-01

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

  14. The chemical bond in inorganic chemistry the bond valence model

    CERN Document Server

    Brown, I David

    2016-01-01

    The bond valence model is a version of the ionic model in which the chemical constraints are expressed in terms of localized chemical bonds formed by the valence charge of the atoms. Theorems derived from the properties of the electrostatic flux predict the rules obeyed by both ionic and covalent bonds. They make quantitative predictions of coordination number, crystal structure, bond lengths and bond angles. Bond stability depends on the matching of the bonding strengths of the atoms, while the conflicting requirements of chemistry and space lead to the structural instabilities responsible for the unusual physical properties displayed by some materials. The model has applications in many fields ranging from mineralogy to molecular biology.

  15. Parental Bonding

    Directory of Open Access Journals (Sweden)

    T. Paul de Cock

    2014-08-01

    Full Text Available Estimating the early parent–child bonding relationship can be valuable in research and practice. Retrospective dimensional measures of parental bonding provide a means for assessing the experience of the early parent–child relationship. However, combinations of dimensional scores may provide information that is not readily captured with a dimensional approach. This study was designed to assess the presence of homogeneous groups in the population with similar profiles on parental bonding dimensions. Using a short version of the Parental Bonding Instrument (PBI, three parental bonding dimensions (care, authoritarianism, and overprotection were used to assess the presence of unobserved groups in the population using latent profile analysis. The class solutions were regressed on 23 covariates (demographics, parental psychopathology, loss events, and childhood contextual factors to assess the validity of the class solution. The results indicated four distinct profiles of parental bonding for fathers as well as mothers. Parental bonding profiles were significantly associated with a broad range of covariates. This person-centered approach to parental bonding has broad utility in future research which takes into account the effect of parent–child bonding, especially with regard to “affectionless control” style parenting.

  16. Structure determination from XAFS using high-accuracy measurements of x-ray mass attenuation coefficients of silver, 11 keV-28 keV, and development of an all-energies approach to local dynamical analysis of bond length, revealing variation of effective thermal contributions across the XAFS spectrum

    Science.gov (United States)

    Tantau, L. J.; Chantler, C. T.; Bourke, J. D.; Islam, M. T.; Payne, A. T.; Rae, N. A.; Tran, C. Q.

    2015-07-01

    We use the x-ray extended range technique (XERT) to experimentally determine the mass attenuation coefficient of silver in the x-ray energy range 11 kev-28 kev including the silver K absorption edge. The results are accurate to better than 0.1%, permitting critical tests of atomic and solid state theory. This is one of the most accurate demonstrations of cross-platform accuracy in synchrotron studies thus far. We derive the mass absorption coefficients and the imaginary component of the form factor over this range. We apply conventional XAFS analytic techniques, extended to include error propagation and uncertainty, yielding bond lengths accurate to approximately 0.24% and thermal Debye-Waller parameters accurate to 30%. We then introduce the FDMX technique for accurate analysis of such data across the full XAFS spectrum, built on full-potential theory, yielding a bond length accuracy of order 0.1% and the demonstration that a single Debye parameter is inadequate and inconsistent across the XAFS range. Two effective Debye-Waller parameters are determined: a high-energy value based on the highly-correlated motion of bonded atoms ({σ\\text{DW}}=0.1413(21) Å), and an uncorrelated bulk value ({σ\\text{DW}}=0.1766(9) Å) in good agreement with that derived from (room-temperature) crystallography.

  17. Structure determination from XAFS using high-accuracy measurements of x-ray mass attenuation coefficients of silver, 11 keV-28 keV, and development of an all-energies approach to local dynamical analysis of bond length, revealing variation of effective thermal contributions across the XAFS spectrum.

    Science.gov (United States)

    Tantau, L J; Chantler, C T; Bourke, J D; Islam, M T; Payne, A T; Rae, N A; Tran, C Q

    2015-07-08

    We use the x-ray extended range technique (XERT) to experimentally determine the mass attenuation coefficient of silver in the x-ray energy range 11 kev-28 kev including the silver K absorption edge. The results are accurate to better than 0.1%, permitting critical tests of atomic and solid state theory. This is one of the most accurate demonstrations of cross-platform accuracy in synchrotron studies thus far. We derive the mass absorption coefficients and the imaginary component of the form factor over this range. We apply conventional XAFS analytic techniques, extended to include error propagation and uncertainty, yielding bond lengths accurate to approximately 0.24% and thermal Debye-Waller parameters accurate to 30%. We then introduce the FDMX technique for accurate analysis of such data across the full XAFS spectrum, built on full-potential theory, yielding a bond length accuracy of order 0.1% and the demonstration that a single Debye parameter is inadequate and inconsistent across the XAFS range. Two effective Debye-Waller parameters are determined: a high-energy value based on the highly-correlated motion of bonded atoms (σ(DW) = 0.1413(21) Å), and an uncorrelated bulk value (σ(DW) = 0.1766(9) Å) in good agreement with that derived from (room-temperature) crystallography.

  18. Optimising hydrogen bonding in solid wood

    DEFF Research Database (Denmark)

    Engelund, Emil Tang

    2009-01-01

    The chemical bonds of wood are both covalent bonds within the wood polymers and hydrogen bonds within and between the polymers. Both types of bonds are responsible for the coherence, strength and stiffness of the material. The hydrogen bonds are more easily modified by changes in load, moisture...... and temperature. The distribution of bond lengths was examined using infrared spectroscopy (ATR-FTIR) both prior to treatments and after. The results show that the absorbance bands of the spectra related to the hydroxyl and carboxyl stretching vibrations were changed by the treatments. Apparently, the first...

  19. Preresonance Raman studies of metal-to-ligand charge transfer in (NH sub 3 ) sub 4 Ru(2,2 prime -bpy) sup 2+. In situ bond length changes, force constants, and reorganization energies

    Energy Technology Data Exchange (ETDEWEB)

    Doorn, S.K.; Hupp, J.T. (Northwestern Univ., Evanston, IL (USA))

    1989-06-21

    As a prototype for charge-transfer reactions in general, the intense metal-to-ligand charge-transfer transition occurring in Ru(NH{sub 3}){sub 4}(bpy){sup 2+} (bpy = 2,2{prime}-bipyridine) has been examined experimentally by resonance and preresonance Raman spectroscopy and analytically by time-dependent scattering theory. To their knowledge, the present example represents the first application of the theory to charge-transfer problems. From the experiments and corresponding theory, the normal-coordinate changes accompanying the transition have been calculated. Both metal-ligand and intraligand bonds are found to distort significantly. When the distortion data are combined with the observed vibrational frequencies, a mode-by-mode assessment of the inner-shell reorganization energy is possible. Further experiments, in which the nature of the solvent is systematically varied, show that selected force constants (and therefore selected components of the internal reorganization energy) are modulated significantly (ca. 6-11 %) by ligand-solvent hydrogen bonding. Finally, variations in the nature of the solvent are found to shift ground- and/or excited-state energies in such a way as to either enhance or attenuate the occurrence of net photochemistry.

  20. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen,and Zhejiang and Guangdong provinces to issue bonds for the first time.How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the Shanghai Securities Journal.Edited excerpts follow.

  1. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen, and Zhejiang and Guangdong provinces to issue bonds for the first time. How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the ShanghaiSecuritiesJournal. Edited excerpts follow:

  2. 1 mil gold bond wire study.

    Energy Technology Data Exchange (ETDEWEB)

    Huff, Johnathon; McLean, Michael B.; Jenkins, Mark W.; Rutherford, Brian Milne

    2013-05-01

    In microcircuit fabrication, the diameter and length of a bond wire have been shown to both affect the current versus fusing time ratio of a bond wire as well as the gap length of the fused wire. This study investigated the impact of current level on the time-to-open and gap length of 1 mil by 60 mil gold bond wires. During the experiments, constant current was provided for a control set of bond wires for 250ms, 410ms and until the wire fused; non-destructively pull-tested wires for 250ms; and notched wires. The key findings were that as the current increases, the gap length increases and 73% of the bond wires will fuse at 1.8A, and 100% of the wires fuse at 1.9A within 60ms. Due to the limited scope of experiments and limited data analyzed, further investigation is encouraged to confirm these observations.

  3. Raman spectroscopy of supported chromium oxide catalysts : determination of chromium-oxygen bond distances and bond orders

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Wachs, I.E.

    1996-01-01

    An empirical correlation is described for relating Raman stretching frequencies of chromium—oxygen (Cr—O) bonds to their bond lengths in chromium oxide reference compounds. An exponential fit of crystallographically determined Cr—O bond lengths to Cr—O Raman symmetric stretching frequencies (800–130

  4. Definition and Application of Topological Index Based on Bond Connectivity

    Institute of Scientific and Technical Information of China (English)

    WANG Zhen-dong; YANG Feng; YANG Hai-lang; LUO Ming-dao; QU Song-sheng

    2003-01-01

    Bond connectivity topological index Si based on chemical bonds was defined by using a matrix method.And Si is formed by atomic parameters such as the number of valence electrons,the number of the highest main quantum of atoms and the bonding electrons and bond parameters such as the length of bonds,the electronegativity difference of bonding atoms.The molecular bond connectivity topological index S is composed of Si.The thermodynamic properties of saturated hydrocarbons,unsaturated hydrocarbons,oxygen organic,methane halide and transitional element compounds and the molecular bond connectivity topological index S have an optimal correlative relationship.

  5. Estimation of genome length

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The genome length is a fundamental feature of a species. This note outlined the general concept and estimation method of the physical and genetic length. Some formulae for estimating the genetic length were derived in detail. As examples, the genome genetic length of Pinus pinaster Ait. and the genetic length of chromosome Ⅵ of Oryza sativa L. were estimated from partial linkage data.

  6. Why are Hydrogen Bonds Directional?

    Indian Academy of Sciences (India)

    ABHISHEK SHAHI; ELANGANNAN ARUNAN

    2016-10-01

    The recent IUPAC recommendation on the definition of hydrogen bonding points out that directionality is a defining characteristic of a hydrogen bond and the angle ∠X-H-Y is generally linear or 180◦. It also suggests that the X-H· · ·Y angle be greater than 110◦ for an interaction to be characterized as a hydrogenbond but does not provide any rationale for the same. This article reports a rationale for limiting the angle, based on the electron density topology using the quantum theory of atoms in molecules. Electron density topology for common hydrogen bond donors HF, HCl, HBr, HNC, HCN and HCCH are reported in this work. These calculations lead to an interesting observation that the atomic basins of H atom in all these donor molecules are limited justifying the restriction of hydrogen bond angle. Moreover, similar analysis on some hydrogen bonded complexes confirms that beyond this angle the acceptor atom Y starts interacting with the atomic basin on X. However, conclusions based on bond lengths and angles have to be treated with care and as the IUPAC recommendation points out that independent ‘evidence for bond formation’ in every case is important.

  7. 通过简单微波法使用新型硫化剂制备HgS纳米颗粒的结构与光谱表征%Structural and spectroscopic characterization of HgS nanoparticles prepared via simple microwave approach in presence of novel sulfuring agent

    Institute of Scientific and Technical Information of China (English)

    Hossein SAFARDOUST-HOJAGHAN; Maryam SHAKOURI-ARANI; Masoud SALAVATI-NIASARI

    2016-01-01

    Mercury sulfide (HgS) crystals with different morphologies and particle sizes, were obtained via a simple microwave reaction by a new precursor complex, [bis ((2-suphanylphenyl)imino]methylphenol) Hg(II)] ([Hg(C13H11NSO)2]2+). The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible (UV−Vis) spectroscopy. Mercury sulfide nanostructures with different sizes were prepared. The effects of precursor concentration, type of solvent, microwave time, and power on the particle size and morphology were investigated. The results show that the type of solvent and microwave power play key roles in the final size of HgS. Ethylene glycol is the best solvent for the synthesis of very fine particles of HgS, and the best power for the preparation of HgS nanoparticles with uniform size distribution is 900 W. The band gap for HgS nanoparticles calculated by UV–Vis spectrum was 3.2 eV which had about 1.2 eV blue shift in comparison with the band gap of 2 eV for bulk sample.%通过简单的微波反应,使用一种新型的前驱体复合物[Hg(C13H11NSO)2]2+,制备具有不同形貌和颗粒尺寸的晶体汞硫化物(HgS)。通过X射线、扫描电镜、紫外−可见光谱对产物进行表征,获得了具有不同尺寸的汞硫化物纳米结构。研究前驱体浓度、溶剂种类、微波时间和功率对产物尺寸和形貌的影响。结果表明:溶剂种类和微波功率极大地影响HgS的最终尺寸。乙二醇是合成细小颗粒HgS的最佳溶剂,制备具有尺寸分布均匀的HgS纳米颗粒的最佳功率是900 W。通过紫外−可见光谱计算出HgS纳米颗粒的带隙是3.2 eV,这相对于块体样品2 eV的带隙蓝移了1.2 eV。

  8. Dissolution, absorption and bioaccumulation in gastrointestinal tract of mercury in HgS-containing traditional medicines Cinnabar and Zuotai%含HgS传统药物朱砂和佐太中汞的胃肠道溶出及吸收蓄积研究

    Institute of Scientific and Technical Information of China (English)

    郑植元; 李岑; 张明; 杨红霞; 耿卢婧; 李林帅; 杜玉枝; 魏立新

    2015-01-01

    中药朱砂和藏药佐太的主要成分分别为α-HgS和β-HgS,但是关于朱砂、佐太、α-HgS和β-HgS中的汞在人体胃肠道中的溶出吸收以及在器官中的分布蓄积的比较研究未见报道.该研究模拟了4种硫化汞类化合物在人体胃肠道中的溶出过程,然后测定汞溶出度,分别比较不同药物间汞溶出度差异以及不同溶液的促溶能力差异.为了探究朱砂和佐太在机体内的吸收蓄积情况,分别以其临床等效剂量灌胃小鼠,同时设置与朱砂等汞量的α-HgS和β-HgS给药组,以及与佐太等汞量的β-HgS和HgC12给药组,然后比较各组不同药物中的汞在小鼠体内吸收蓄积能力差异以及小鼠不同组织器官对汞的蓄积能力差异.实验结果表明,佐太在人工胃肠液中的汞溶出度均较大,其次是β-HgS,朱砂和α-HgS也有一定的溶出.对于小鼠汞吸收蓄积实验,HgCl2吸收蓄积能力最强,β-HgS其次,α-HgS略强于朱砂;不同器官对汞的蓄积能力大小依次是肾>肝>脑.该研究贴近临床实际,观察含汞药物朱砂和佐太在胃肠道中的溶出以及吸收分布蓄积,为临床安全用药提供参考,也希望为含重金属药物的安全性评价提供研究模式.%α-HgS is the main component of traditional Chinese medicine cinnabar,while β-HgS is the main component of Tibetan medicine Zuotai.However,there was no comparative study on the dissolution and absorption in gastrointestinal tract and bioaccumulation in organs of mercury in Cinnabar,Zuotai,α-HgS and β-HgS.In this study,the dissolution process of the four compounds in the human gastrointestinal tract was simulated to determine the mercury dissolutions and compare the mercury dissolution of different medicines and the dissolution-promoting capacity of different solutions.To explore the absorption and bioaccumulation of cinnabar and Zuotai in organisms,mice were orally administered with clinical equivalent doses cinnabar and Zuotai

  9. Understanding Bonds - Denmark

    DEFF Research Database (Denmark)

    Rimmer, Nina Røhr

    2016-01-01

    a specified rate of interest during the life of the bond and to repay the face value of the bond (the principal) when it “matures,” or comes due. Among the types of bonds you can choose from are: Government securities, municipal bonds, corporate bonds, mortgage and asset-backed securities, federal agency...

  10. Bond valence at mixed occupancy sites. I. Regular polyhedra.

    Science.gov (United States)

    Bosi, Ferdinando

    2014-10-01

    Bond valence sum calculations at mixed occupancy sites show the occurrence of systematic errors leading to apparent violations of the Valence Sum Rule (bond valence theory) in regular and unstrained bonding environments. The systematic deviation of the bond valence from the expected value is observed in the long-range structure, and is discussed from geometric and algebraic viewpoints. In the valence-length diagram, such a deviation arises from discrepancies between the intersection points of the long-range bond valences and the theoretical bond valences with the valence-length curves of involved cations. Three factors cause systematic errors in the bond valences: difference in atomic valences, bond valence parameters Ri (the length of a bond of unit valence) and bond valence parameters bi (the bond softness) between the involved cations over the same crystallographic site. One important consequence strictly related to the systematic errors is that they lead to erroneous bond strain values for mixed occupancy sites indicating underbonding or overbonding that actually does not exist.

  11. Measuring Thermodynamic Length

    Energy Technology Data Exchange (ETDEWEB)

    Crooks, Gavin E

    2007-09-07

    Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

  12. Cross Shear Roll Bonding

    DEFF Research Database (Denmark)

    Bay, Niels; Bjerregaard, Henrik; Petersen, Søren. B;

    1994-01-01

    The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20......-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results....

  13. Wire bonding in microelectronics

    CERN Document Server

    Harman, George G

    2010-01-01

    Wire Bonding in Microelectronics, Third Edition, has been thoroughly revised to help you meet the challenges of today's small-scale and fine-pitch microelectronics. This authoritative guide covers every aspect of designing, manufacturing, and evaluating wire bonds engineered with cutting-edge techniques. In addition to gaining a full grasp of bonding technology, you'll learn how to create reliable bonds at exceedingly high yields, test wire bonds, solve common bonding problems, implement molecular cleaning methods, and much more. Coverage includes: Ultrasonic bonding systems and technologies, including high-frequency systems Bonding wire metallurgy and characteristics, including copper wire Wire bond testing Gold-aluminum intermetallic compounds and other interface reactions Gold and nickel-based bond pad plating materials and problems Cleaning to improve bondability and reliability Mechanical problems in wire bonding High-yield, fine-pitch, specialized-looping, soft-substrate, and extreme-temperature wire bo...

  14. Bond behaviour of GFRP reinforced geopolymer cement concrete

    Directory of Open Access Journals (Sweden)

    Hailu Tekle Biruk

    2017-01-01

    Full Text Available Bond plays a key role in the performance of reinforced concrete structures. Glass fibre reinforced polymer (GFRP reinforcing bar and Geopolymer cement (GPC concrete are promising alternative construction materials for steel bars and Ordinary Portland Cement (OPC concrete respectively. In this study, the bond behaviour between these two materials is investigated by using beam-end specimen tests. The bond behaviour of 15.9 mm diameter sand-coated GFRP bar was investigated. An embedment length of six and nine times the bar diameter were used. The free end and the loaded end bond-slip-relationships, the bond failure mode and the average bond stress were used to analyse each of the specimens. Additionally, the distribution of tensile and bond stress along the embedment length was investigated by installing strain gauges along the embedment length in some of the specimens. Test results indicate that a significant difference exists between the free end and loaded end bond-slip curves, which is due to the lower elastic modulus of the GFRP bars. Furthermore, it was found that the tensile and bond stress distribution along the embedment length is nonlinear and the nonlinearity changes with the load.

  15. Minimum Length - Maximum Velocity

    CERN Document Server

    Panes, Boris

    2011-01-01

    We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example we can predict the ratio between the minimum lengths in space and time using the results from OPERA about superluminal neutrinos.

  16. Telomere length and depression

    DEFF Research Database (Denmark)

    Wium-Andersen, Marie Kim; Ørsted, David Dynnes; Rode, Line

    2016-01-01

    BACKGROUND: Depression has been cross-sectionally associated with short telomeres as a measure of biological age. However, the direction and nature of the association is currently unclear. AIMS: We examined whether short telomere length is associated with depression cross-sectionally as well...... as prospectively and genetically. METHOD: Telomere length and three polymorphisms, TERT, TERC and OBFC1, were measured in 67 306 individuals aged 20-100 years from the Danish general population and associated with register-based attendance at hospital for depression and purchase of antidepressant medication....... RESULTS: Attendance at hospital for depression was associated with short telomere length cross-sectionally, but not prospectively. Further, purchase of antidepressant medication was not associated with short telomere length cross-sectionally or prospectively. Mean follow-up was 7.6 years (range 0...

  17. Myofilament length dependent activation

    Energy Technology Data Exchange (ETDEWEB)

    de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

    2010-05-25

    The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

  18. A Characteristic Particle Length

    CERN Document Server

    Roberts, Mark D

    2015-01-01

    It is argued that there are characteristic intervals associated with any particle that can be derived without reference to the speed of light $c$. Such intervals are inferred from zeros of wavefunctions which are solutions to the Schr\\"odinger equation. The characteristic length is $\\ell=\\beta^2\\hbar^2/(8Gm^3)$, where $\\beta=3.8\\dots$; this length might lead to observational effects on objects the size of a virus.

  19. Observations on oesophageal length.

    Science.gov (United States)

    Kalloor, G J; Deshpande, A H; Collis, J L

    1976-01-01

    The subject of oesophageal length is discussed. The great variations in the length of the oesophagus in individual patients is noted, and the practical use of its recognition in oesophageal surgery is stressed. An apprasial of the various methods available for this measurement is made; this includes the use of external chest measurement, endoscopic measurement, and the measurement of the level of the electrical mucosal potential change. Correlative studies of these various methods are made, and these show a very high degree of significance. These studies involved simultaneous measurement of external and internal oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal reflux symptoms, 42 patients with sliding type hiatal hernia, and 17 patients with a peptic stricture in association with hiatal hernia. The method of measuring oesophageal length by the use of the external chest measurement, that is, the distance between the lower incisor teeth and the xiphisternum, measured with the neck fully extended and the patient lying supine, is described in detail, its practical application in oesophageal surgery is illustrated, and its validity tested by internal measurements. The findings of this study demonstrate that the external chest measurement provides a mean of assessing the true static length of the oesophagus, corrected for the size of the individual. Images PMID:941114

  20. Bond Alternation, Polarizability and Resonance Detuning in Methine Dyes

    CERN Document Server

    Olsen, Seth

    2010-01-01

    Many organic molecules with a high nonlinear polarizability have a "Brooker dye" structure, featuring electron accepting or donating groups separated by an unsaturated (methine or polyene) hydrocarbon bridge. These systems have been the topic of much discussion with regard to their structure-property relationships - particularly relationships linking nonlinear response to bond-length alternation. Here, we show that these relationships can be subsumed within the conceptual framework of a Brooker dye color proposed by Platt [J.R. Platt, J. Chem. Phys. 25 80 (1956)]. The key quantities of Platt's model are the Brooker basicity difference and the isoexcitation energy. These concepts provide a spectroscopic definition of the resonant (cyanine) limit, which is independent of other descriptors commonly used (e.g. bond length alternation). We establish a relation ship between the bond length and the Brooker basicity difference, with which we establish a natural origin for bond length alternation coordinates in asymme...

  1. Bond Properties and Experimental Methods of Textile Reinforced Concrete

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Textile reinforced concrete(TRC, for short) allows the low size production and offers a high effectiveness of the reinforcement by using continuous roving instead of short-chopped fibers. However, whether textiles can cooperate with concrete very well depends on the bond between them. In this paper, the bonding mechanism that the stress was transferred from fine concrete to textile was analyzed, and the influences of the initial bond length of textile, the surface treatment of textile, the strength and workability of concrete as well as the level of prestressing force on bond behavior were investigated on the basis of pull-out tests. The results reveal that with initial bond length increasing, the maximum pull force increases, and increasing concrete strength and improving workability of concrete matrix, epoxy resin impregnating and sand covering of textile as well as prestressing textile can obviously increase the bond strength between the textile and concrete.

  2. Bonded and Stitched Composite Structure

    Science.gov (United States)

    Zalewski, Bart F. (Inventor); Dial, William B. (Inventor)

    2014-01-01

    A method of forming a composite structure can include providing a plurality of composite panels of material, each composite panel having a plurality of holes extending through the panel. An adhesive layer is applied to each composite panel and a adjoining layer is applied over the adhesive layer. The method also includes stitching the composite panels, adhesive layer, and adjoining layer together by passing a length of a flexible connecting element into the plurality of holes in the composite panels of material. At least the adhesive layer is cured to bond the composite panels together and thereby form the composite structure.

  3. Fatigue de-bond growth in adhesively bonded single lap joints

    Indian Academy of Sciences (India)

    P K Sahoo; B Dattaguru; C M Manjunatha; C R L Murthy

    2012-02-01

    The fatigue de-bond growth studies have been conducted on adhesively bonded lap joint specimens between aluminium and aluminium with Redux-319A adhesive with a pre-defined crack of 3 mm at the bond end. The correlations between fracture parameters and the de-bond growth data are established using both numerical and experimental techniques. In the numerical method, geometrically non-linear finite element analyses were carried out on adhesively bonded joint specimen for various de-bond lengths measured from the lap end along the mid-bond line of the adhesive. The finite element results were post processed to estimate the SERR components $G_I$ and $G_{II}$ using the Modified Virtual Crack Closure Integral (MVCCI) procedure. In experimental work, specimens were fabricated and fatigue de-bond growth tests were conducted at a stress ratio $R = −1$. The results obtained from both numerical analyses and testing have been used to generate de-bond growth curve and establish de-bond growth law in the Paris regime for such joints. The de-bond growth rate is primarily function of mode-I SERR component $G_I$ since the rate of growth in shear mode is relatively small. The value of Paris exponent is found to be 6.55. The high value of de-bond growth exponent in Paris regime is expected, since the adhesive is less ductile than conventional metallic materials. This study is important for estimating the life of adhesively bonded joints under both constant and variable amplitude fatigue loads.

  4. Bonding with Your Baby

    Science.gov (United States)

    ... in infant massage in your area. Breastfeeding and bottle-feeding are both natural times for bonding. Infants respond ... activities include: participating together in labor and delivery feeding ( breast or bottle ); sometimes dad forms a special bond with baby ...

  5. Bond percolation in films

    Science.gov (United States)

    Korneta, W.; Pytel, Z.

    1988-04-01

    Bond percolation in films with simple cubic structure is considered. It is assumed that the probability of a bond being present between nearest-neighbor sites depends on the distances to surfaces. Based on the relation between the Potts model and the bond percolation model, and using the mean-field approximation, the phase diagram and profiles of the percolation probability have been obtained.

  6. Acrylic mechanical bond tests

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Alkyl Radicals as Hydrogen Bond Acceptors: Computational Evidence

    DEFF Research Database (Denmark)

    Hammerum, Steen

    2009-01-01

    , and gives rise to pronounced shifts of IR stretching frequencies and to increased absorption intensities. The hydrogen bond acceptor properties of alkyl radicals equal those of many conventional acceptors, e.g., the bond length changes and IR red-shifts suggest that tert-butyl radicals are slightly better...

  8. Chemical bond fundamental aspects of chemical bonding

    CERN Document Server

    Frenking, Gernot

    2014-01-01

    This is the perfect complement to ""Chemical Bonding - Across the Periodic Table"" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemica

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

    Science.gov (United States)

    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.

  10. Homolytic Bond Dissociation Enthalpies of C C and C-H Bonds in Highly Crowded Alkanes

    Institute of Scientific and Technical Information of China (English)

    ZHU Chen; RUI Lei; FU Yao

    2008-01-01

    The homolytic C-C and C--H bond dissociation enthalpyies (BDE) of highly crowded alkanes were calcu- lated by using an ONIOM-G3B3 method. Geometric parameters such as bond length, bond angle and molecular volume were carefully investigated, as most of the acyclic alkanes in this study were not yet synthesized. These pa-rameters reflect the influence of steric effect on BDE. Good correlations were found between the rapid decrease of BDE and the increase of molecular volumes. The correlations can be applied to the prediction of the possible exis-tence of many highly strained compounds.

  11. Extraordinarily Long 2-Electron - 4-Center (2e-/4c) 2.9-Å Carbon-Carbon Bonds - What is a Chemical Bond?

    OpenAIRE

    Miller, Joel S.

    2014-01-01

    Carbon-carbon (CC) bonding is a key essence of organic and biochemistry. The length of a CC bond, i.e. 1.54 Å found in the diamond allotrope of carbon and ethane, is among the essential information learned by all chemistry students. This is the length of a single bond () between sp3-hybridized carbons and is the longest of all common CC bonds. Our studies of the [TCNE]22- (TCNE = tetracyanoethylene) dimers reveal that 2.89 ± 0.05 Å 2 electron/4 center (2e-/4c) CC bonds are present. Struc...

  12. Mappability and Read Length

    Directory of Open Access Journals (Sweden)

    Wentian eLi

    2014-11-01

    Full Text Available Power-law distributions are the main functional form forthe distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size offragments and reads may prevent an unique alignment of repeatsequences to the reference sequence. Repeats in the human genome canbe as long as $10^4$ bases, or $10^5-10^6$ bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of $10^3$ bases.With the read length of exactly 1000 bases, slightly more than 1% of theassembled genome, and slightly less than 1% of the 1kbreads, are unmappable, excluding the unassembled portion of the humangenome (8% in GRCh37. The slow decay (long tail ofthe power-law function implies a diminishing return in convertingunmappable regions/reads to become mappable with the increase of theread length, with the understanding that increasing read length willalways move towards the direction of 100% mappability.

  13. Telomere Length and Mortality

    DEFF Research Database (Denmark)

    Kimura, Masayuki; Hjelmborg, Jacob V B; Gardner, Jeffrey P

    2008-01-01

    telomeres predicted the death of the first co-twin better than the mTRFL did (mTRFL: 0.56, 95% confidence interval (CI): 0.49, 0.63; mTRFL(50): 0.59, 95% CI: 0.52, 0.66; mTRFL(25): 0.59, 95% CI: 0.52, 0.66; MTRFL: 0.60, 95% CI: 0.53, 0.67). The telomere-mortality association was stronger in years 3-4 than......Leukocyte telomere length, representing the mean length of all telomeres in leukocytes, is ostensibly a bioindicator of human aging. The authors hypothesized that shorter telomeres might forecast imminent mortality in elderly people better than leukocyte telomere length. They performed mortality...... analysis in 548 same-sex Danish twins (274 pairs) aged 73-94 years, of whom 204 pairs experienced the death of one or both co-twins during 9-10 years of follow-up (1997-2007). From the terminal restriction fragment length (TRFL) distribution, the authors obtained the mean TRFL (mTRFL) and the mean values...

  14. Relativistic length agony continued

    Directory of Open Access Journals (Sweden)

    Redžić D.V.

    2014-01-01

    Full Text Available We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redžić 2008b, we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the ‘pole in a barn’ paradox. [Projekat Ministarstva nauke Republike Srbije, br. 171028

  15. Bond Strength of Composite CFRP Reinforcing Bars in Timber

    Directory of Open Access Journals (Sweden)

    Marco Corradi

    2015-07-01

    Full Text Available The use of near-surface mounted (NSM fibre-reinforced polymer (FRP bars is an interesting method for increasing the shear and flexural strength of existing timber members. This article examines the behaviour of carbon FRP (CFRP bars in timber under direct pull-out conditions. The objective of this experimental program is to investigate the bond strength between composite bars and timber: bars were epoxied into small notches made into chestnut and fir wood members using a commercially-available epoxy system. Bonded lengths varied from 150 to 300 mm. Failure modes, stress and strain distributions and the bond strength of CFRP bars have been evaluated and discussed. The pull-out capacity in NSM CFRP bars at the onset of debonding increased with bonded length up to a length of 250 mm. While CFRP bar’s pull-out was achieved only for specimens with bonded lengths of 150 and 200 mm, bar tensile failure was mainly recorded for bonded lengths of 250 and 300 mm.

  16. Ground Wood Fiber Length Distributions

    OpenAIRE

    Lauri Ilmari Salminen; Sari Liukkonen; Alava, Mikko J.

    2014-01-01

    This study considers ground wood fiber length distributions arising from pilot grindings. The empirical fiber length distributions appear to be independent of wood fiber length as well as feeding velocity. In terms of mathematics the fiber fragment distributions of ground wood pulp combine an exponential distribution for high-length fragments and a power-law distribution for smaller lengths. This implies that the fiber length distribution is influenced by the stone surface. A fragmentation-ba...

  17. The Bondons: The Quantum Particles of the Chemical Bond

    Directory of Open Access Journals (Sweden)

    Mihai V. Putz

    2010-10-01

    Full Text Available By employing the combined Bohmian quantum formalism with the U(1 and SU(2 gauge transformations of the non-relativistic wave-function and the relativistic spinor, within the Schrödinger and Dirac quantum pictures of electron motions, the existence of the chemical field is revealed along the associate bondon particle  characterized by its mass (mΒ, velocity (vΒ, charge (eΒ, and life-time (tΒ. This is quantized either in ground or excited states of the chemical bond in terms of reduced Planck constant ħ, the bond energy Ebond and length Xbond, respectively. The mass-velocity-charge-time quaternion properties of bondons’ particles were used in discussing various paradigmatic types of chemical bond towards assessing their covalent, multiple bonding, metallic and ionic features. The bondonic picture was completed by discussing the relativistic charge and life-time (the actual zitterbewegung problem, i.e., showing that the bondon equals the benchmark electronic charge through moving with almost light velocity. It carries negligible, although non-zero, mass in special bonding conditions and towards observable femtosecond life-time as the bonding length increases in the nanosystems and bonding energy decreases according with the bonding length-energy relationship Ebond[kcal/mol]*Xbond[A]=182019, providing this way the predictive framework in which the particle may be observed. Finally, its role in establishing the virtual states in Raman scattering was also established.

  18. Copper wire bonding

    CERN Document Server

    Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

    2014-01-01

    This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

  19. How universal are hydrogen bond correlations? A density functional study of intramolecular hydrogen bonding in low-energy conformers of α-amino acids

    Science.gov (United States)

    Ramaniah, Lavanya M.; Kamal, C.; Kshirsagar, Rohidas J.; Chakrabarti, Aparna; Banerjee, Arup

    2013-10-01

    Hydrogen bonding is one of the most important and ubiquitous interactions present in Nature. Several studies have attempted to characterise and understand the nature of this very basic interaction. These include both experimental and theoretical investigations of different types of chemical compounds, as well as systems subjected to high pressure. The O-H..O bond is of course the best studied hydrogen bond, and most studies have concentrated on intermolecular hydrogen bonding in solids and liquids. In this paper, we analyse and characterise normal hydrogen bonding of the general type, D-H...A, in intramolecular hydrogen bonding interactions. Using a first-principles density functional theory approach, we investigate low energy conformers of the twenty α-amino acids. Within these conformers, several different types of intramolecular hydrogen bonds are identified. The hydrogen bond within a given conformer occurs between two molecular groups, either both within the backbone itself, or one in the backbone and one in the side chain. In a few conformers, more than one (type of) hydrogen bond is seen to occur. Interestingly, the strength of the hydrogen bonds in the amino acids spans quite a large range, from weak to strong. The signature of hydrogen bonding in these molecules, as reflected in their theoretical vibrational spectra, is analysed. With the new first-principles data from 51 hydrogen bonds, various parameters relating to the hydrogen bond, such as hydrogen bond length, hydrogen bond angle, bond length and vibrational frequencies are studied. Interestingly, the correlation between these parameters in these bonds is found to be in consonance with those obtained in earlier experimental studies of normal hydrogen bonds on vastly different systems. Our study provides some of the most detailed first-principles support, and the first involving vibrational frequencies, for the universality of hydrogen bond correlations in materials.

  20. A DFT Study on Intramolecular Hydrogen Bond in Substituted Catechols and Their Radicals

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted catechols and their radicals generated after H-abstraction. It was found that although the charge difference between hydrogen-bonded H and O played a role in determining HIHB, HIHB was mainly governed by the hydrogen bond length. As the oxygen-centered radical has great tendency to form a chemical bond with the H atom, hydrogen bond lengths in catecholic radicals are systematically shorter than those in catechols. Hence, the HIHB for the former are higher than those for the latter.

  1. Theoretical study for Bond between Reinforcement steel and Concrete

    Directory of Open Access Journals (Sweden)

    usama mostafa mahran

    2013-04-01

    Full Text Available The behavior and load carrying behavior of reinforced concrete structures is influence by the interaction between the concrete and reinforcement. The stress transfer between reinforcement and concrete in the longitudinal direction of the bars is called bond. An essential feature of reinforced concrete is the bond between steel and concrete. Anchorage of reinforcement depends on the bond between steel and concrete, crack width and crack spacing are mainly governed by it. So, stiffness, deformation and dynamic behavior are influenced by it, and in reverse loading damping and energy dissipation is a function of bond. This is one of the reasons why bond has been, and still is, a topic of fundamental and applied research. Bond stress is the equivalent unit shear stress acting in parallel to the reinforcing bar on the interface between reinforcing steel bar and concrete. Due to the transfer of forces through bond stress, between the reinforcing rebar and concrete, the force in the reinforcing bar changes along its length. Because bond stress is thought of as stress per unit area of bar surface, it is related to the rate of change of steel stress. Consequently, to have bond stress it is necessary to have a changing steel stress. In cases of high stress at the contact interface, near cracks or end anchorages, the bond stresses are related to relative displacements between concrete and steel. These relative displacements, which are caused by different average strains in the concrete and the steel, are usually called bond-slip (t-d.

  2. discouraged by queue length

    Directory of Open Access Journals (Sweden)

    P. R. Parthasarathy

    2001-01-01

    Full Text Available The transient solution is obtained analytically using continued fractions for a state-dependent birth-death queue in which potential customers are discouraged by the queue length. This queueing system is then compared with the well-known infinite server queueing system which has the same steady state solution as the model under consideration, whereas their transient solutions are different. A natural measure of speed of convergence of the mean number in the system to its stationarity is also computed.

  3. Comparison of Gold Bonding with Mercury Bonding

    NARCIS (Netherlands)

    Kraka, Elfi; Filatov, Michael; Cremer, Dieter

    2009-01-01

    Nine AuX molecules (X = H, O, S, Se, Te, F, Cl, Br, I), their isoelectronic HgX(+) analogues, and the corresponding neutral HgX diatomics have been investigated using NESC (Normalized Elimination of the Small Component) and B3LYP theory to determine relativistic effects for bond dissociation energie

  4. Comparison of Gold Bonding with Mercury Bonding

    NARCIS (Netherlands)

    Kraka, Elfi; Filatov, Michael; Cremer, Dieter

    2009-01-01

    Nine AuX molecules (X = H, O, S, Se, Te, F, Cl, Br, I), their isoelectronic HgX(+) analogues, and the corresponding neutral HgX diatomics have been investigated using NESC (Normalized Elimination of the Small Component) and B3LYP theory to determine relativistic effects for bond dissociation

  5. The dissociative bond.

    Science.gov (United States)

    Gordon, Nirit

    2013-01-01

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

  6. The samurai bond market

    OpenAIRE

    1997-01-01

    Issuance in the samurai bond market has more than tripled over the past several years. Some observers have attributed this growth to a systematic underestimation of credit risk in the market. A detailed review of credit quality, ratings differences, and initial issue pricing in the samurai bond market, however, turns up little evidence to support this concern.

  7. Theoretical study of the interplay between lithium bond and hydrogen bond in complexes involved with HLi and HCN.

    Science.gov (United States)

    Li, Qingzhong; Hu, Ting; An, Xiulin; Li, Wenzuo; Cheng, Jianbo; Gong, Baoan; Sun, Jiazhong

    2009-12-21

    The lithium- and hydrogen-bonded complex of HLi-NCH-NCH is studied with ab initio calculations. The optimized structure, vibrational frequencies, and binding energy are calculated at the MP2 level with 6-311++G(2d,2p) basis set. The interplay between lithium bonding and hydrogen bonding in the complex is investigated with these properties. The effect of lithium bonding on the properties of hydrogen bonding is larger than that of hydrogen bonding on the properties of lithium bonding. In the trimer, the binding energies are increased by about 19% and 61% for the lithium and hydrogen bonds, respectively. A big cooperative energy (-5.50 kcal mol(-1)) is observed in the complex. Both the charge transfer and induction effect due to the electrostatic interaction are responsible for the cooperativity in the trimer. The effect of HCN chain length on the lithium bonding has been considered. The natural bond orbital and atoms in molecules analyses indicate that the electrostatic force plays a main role in the lithium bonding. A many-body interaction analysis has also been performed for HLi-(NCH)(N) (N=2-5) systems.

  8. Corporate Bonds in Denmark

    DEFF Research Database (Denmark)

    Tell, Michael

    2015-01-01

    Corporate financing is the choice between capital generated by the corporation and capital from external investors. However, since the financial crisis shook the markets in 2007–2008, financing opportunities through the classical means of financing have decreased. As a result, corporations have...... to think in alternative ways such as issuing corporate bonds. A market for corporate bonds exists in countries such as Norway, Germany, France, the United Kingdom and the United States, while Denmark is still behind in this trend. Some large Danish corporations have instead used foreign corporate bonds...... markets. However, NASDAQ OMX has introduced the First North Bond Market in December 2012 and new regulatory framework came into place in 2014, which may contribute to a Danish based corporate bond market. The purpose of this article is to present the regulatory changes in Denmark in relation to corporate...

  9. Perimeter ring currents in benzenoids from Pauling bond orders.

    Science.gov (United States)

    Fowler, Patrick W; Myrvold, Wendy; Jenkinson, Daniel; Bird, William H

    2016-04-28

    It is shown that the ring currents in perimeter hexagonal rings of Kekulean benzenoids, as estimated within the Randić conjugated-circuit model, can be calculated directly without tedious pairwise comparison of Kekulé structures or Kekulé counting for cycle-deleted subgraphs. Required are only the Pauling bond orders of perimeter bonds and the number of Kekulé structures of the benzenoid, both readily available from the adjacency matrix of the carbon skeleton. This approach provides easy calculation of complete current maps for benzenoids in which every face has at least one bond on the perimeter (as in the example of cata-condensed benzenoids), and allows qualitative evaluation of the main ring-current contributions to (1)H chemical shifts in general benzenoids. A combined Randić-Pauling model for correlation of ring current and bond length through bond order is derived and shown to be consistent with resilience of current under bond alternation.

  10. Anisotropic bond percolation in two dimensions

    Science.gov (United States)

    Arovas, D.; Bhatt, R. N.; Shapiro, B.

    1983-08-01

    A new single-parameter renormalization-group equation is formulated for anisotropic bond percolation in two dimensions using a position-space renormalization approach. The new equation yields the exact critical line px+py=1 within both the Migdal-Kadanoff decimation and cell renormalization schemes. For large anisotropy, however, an additional critical line appears leading to a spurious divergence in the correlation-length critical exponent. An alternative scheme, which does not preserve the exact critical surface, but yields a correlation-length exponent relatively independent of anisotropy, is also examined.

  11. Comparison and Research of Cinnabar, Zhusha Anshen Wan and HgS on Rat Absorption and Distribution%朱砂、朱砂安神丸及氯化汞在小鼠体内吸收、分布对比

    Institute of Scientific and Technical Information of China (English)

    付中祥; 杨虹; 陈秀芬; 刘杰; 时京珍

    2013-01-01

    目的:对比研究朱砂、朱砂安神丸及氯化汞在小鼠体内的吸收、分布规律.方法:昆明种小鼠180只,分为正常组、朱砂临床剂量组(0.2 g·kg-1,ig)、朱砂高剂量组(11.2 g·kg-1,ig)、朱砂安神丸组(2 g·kg-1,ig)、氯化汞组(0.07 g·kg-1,ig),每组小鼠在给药1,2,4,8,16,24 h后各取6只鼠的血、脑、肝、肾,原子荧光光度法检测汞含量.结果:朱砂临床剂量组和朱砂安神丸组体内最大血药浓度及各时间点血药浓度与氯化汞组相比具有明显差异(P<0.05);朱砂临床剂量组与朱砂安神丸组各时间点肝、肾组织中汞含量与氯化汞组有显著性差异(p< 0.05);朱砂临床剂量组和朱砂高剂量组在血液和组织中汞含量亦有显著性差异(P<0.05);朱砂高剂量组脑中汞含量最高.结论:临床剂量的朱砂、朱砂安神丸的汞吸收及各组织的汞含量均明显低于高剂量的朱砂和氯化汞.%Objective: To study the regulation of Cinnabar, Zhusha Anshen wan (ZSASW) and HgS on absorption and distribution in mice. Method: Oral gavage was given to Kunming mice with cinnabar (0. 2 g · kg-1), high dose of cinnabar (11.2 g·kg-1), ZSASW (2g·kg-1) , HgS (0.07 g·kg-1) or saline daily for 1, 2, 4, 8, 16, 24 hours, mercury accumulation in blood, liver, kidney and brain was determined by atomic fluoresence detector. Result: In comparison, the maximal serum concentration and serum concentration in each time of cinnabar clinical dose group and ZSASW group have obvious difference with the HgCl2 group. The mercury accumulation in liver and kidney in each time of clinical dose group and ZSASW group have obvious difference with the HgCl2 group. The mercury accumulation in blood and organs also had obvious difference between cinnabar clinical dose group and high dose group, and the high dose has the maximal accumulation in brain. Conclusion: Both cinnabar clinical dose group and ZSASW group have obvious difference with cinnabar high

  12. Modelling of Ion Transport in Solids with a General Bond Valence Based Force-Field

    OpenAIRE

    Adams, S.; R.P. Rao

    2010-01-01

    Empirical bond length - bond valence relations provide insight into the link between structure of and ion transport in solid electrolytes. Building on our earlier systematic adjustment of bond valence (BV) parameters to the bond softness, here we discuss how the squared BV mismatch can be linked to the absolute energy scale and used as a general Morse-type interaction potential for analyzing low-energy pathways in ion conducting solid or mixed conductors either by an energy landscape approach...

  13. Effect of ultrasonic power and bonding force on the bonding strength of copper ball bonds

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the efficient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.

  14. Transversely Compressed Bonded Joints

    DEFF Research Database (Denmark)

    Hansen, Christian Skodborg; Schmidt, Jacob Wittrup; Stang, Henrik

    2012-01-01

    The load capacity of bonded joints can be increased if transverse pressure is applied at the interface. The transverse pressure is assumed to introduce a Coulomb-friction contribution to the cohesive law for the interface. Response and load capacity for a bonded single-lap joint was derived using...... non-linear fracture mechanics. The results indicated a good correlation between theory and tests. Furthermore, the model is suggested as theoretical base for determining load capacity of bonded anchorages with transverse pressure, in externally reinforced concrete structures....

  15. Ground Wood Fiber Length Distributions

    Directory of Open Access Journals (Sweden)

    Lauri Ilmari Salminen

    2014-01-01

    Full Text Available This study considers ground wood fiber length distributions arising from pilot grindings. The empirical fiber length distributions appear to be independent of wood fiber length as well as feeding velocity. In terms of mathematics the fiber fragment distributions of ground wood pulp combine an exponential distribution for high-length fragments and a power-law distribution for smaller lengths. This implies that the fiber length distribution is influenced by the stone surface. A fragmentation-based model is presented that allows reproduction of the empirical results.

  16. EXPERIMENTAL INVESTIGATION ON THE EFFECT OF NATURAL TROPICAL WEATHER ON INTERFACIAL BONDING PERFORMANCE OF CFRP-CONCRETE BONDING SYSTEM

    Directory of Open Access Journals (Sweden)

    MOHD H. MOHD HASHIM

    2016-04-01

    Full Text Available The existing reinforced concrete structures may require rehabilitation and strengthening to overcome deficiencies due to defect and environmental deterioration. Fibre Reinforced Polymer (FRP-concrete bonding systems can provide solution for the deficiencies, but the durability of the bonded joint needs to be investigated for reliable structural performance. In this research the interfacial bonding behaviour of CFRP-concrete system under tropical climate exposure is main interest. A 300 mm concrete prism was bonded with CFRP plate on its two sides and exposed for 3, 6, and 9 months to laboratory environment, continuous natural weather, and wet-dry exposure in 3.5% saltwater solution at room and 40 °C temperature. The prisms were subjected to tension and compression load under bonding test to measure the strain and determine stress distribution and shear stress transfer behaviour. The results of the bonding test showed that load transfer was fairly linear and uniform at lower load level and changed to non-linear and non- uniform at higher load level. The force transfers causes the shear stress distribution being shifted along the bonded length. The combination of climate effects may have provided better curing of the bonded joints, but longer duration of exposure may be required to weaken the bond strength. Nevertheless, CFRP-concrete bonding system was only minimally affected under the tropical climate and salt solution.

  17. Handbook of wafer bonding

    CERN Document Server

    Ramm, Peter; Taklo, Maaike M V

    2011-01-01

    Written by an author and editor team from microsystems companies and industry-near research organizations, this handbook and reference presents dependable, first-hand information on bonding technologies.In the first part, researchers from companies and institutions around the world discuss the most reliable and reproducible technologies for the production of bonded wafers. The second part is devoted to current and emerging applications, including microresonators, biosensors and precise measuring devices.

  18. Effect of coordination on bond properties: A first principles study

    Indian Academy of Sciences (India)

    Jaita Paul; Shobhana Narasimhan

    2008-06-01

    We have used density functional theory to obtain the binding curves for a variety of hypothetical periodic structures of Al, Si, Pb, Sn and Au. Upon examining the resulting database of results for equilibrium bond lengths and radial force constants (within a nearest-neighbour model), we find that both decrease smoothly as coordination is reduced. The effect of dimensionality appears to be small. We find that the force constants at equilibrium vary as the inverse eighth power of the equilibrium bond length. We also find evidence that the force constants are sensitive only to the bond length, and not to the coordination number. We believe these results will be useful in formulating interatomic potentials, e.g., for nanosystems.

  19. Modelling longevity bonds: Analysing the Swiss Re Kortis bond

    OpenAIRE

    2015-01-01

    A key contribution to the development of the traded market for longevity risk was the issuance of the Kortis bond, the world's first longevity trend bond, by Swiss Re in 2010. We analyse the design of the Kortis bond, develop suitable mortality models to analyse its payoff and discuss the key risk factors for the bond. We also investigate how the design of the Kortis bond can be adapted and extended to further develop the market for longevity risk.

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

    Science.gov (United States)

    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

  1. Effects of chain length and Au spin-orbit coupling on 3(pi pi*) emission from bridging Cn2- units: theoretical characterization of spin-forbidden radiative transitions in metal-capped one-dimensional carbon chains [H3PAu(C[triple bond]C)nAuPH3].

    Science.gov (United States)

    Cao, Zexing; Zhang, Qianer

    2004-04-19

    Density functional theory and CASSCF calculations have been used to optimize the geometries of binuclear gold(I) complexes [H(3)PAu(C[triple bond]C)(n)AuPH(3)] (n=1-6) in their ground states and selected lowest energy (3)(pi pi*) excited states. Vertical excitation energies obtained by time-dependent density functional calculations for the spin-forbidden singlet-triplet transitions have exponential-decay size dependence. The predicted singlet-triplet splitting limit of [H(3)PAu(C[triple bond]C)(proportional/variant)AuPH(3)] is about 8317 cm(-1). Calculated singlet-triplet transition energies are in reasonable agreement with available experimental observations. The effect of the heavy atom Au spin-orbit coupling on the (3)(pi pi*) emission of these metal-capped one-dimensional carbon allotropes has been investigated by MRCI calculations. The contribution of the spin- and dipole-allowed singlet excited state to the spin-orbit-coupling wave function of the (3)(pi pi*) excited state makes the low-lying acetylenic triplet excited states become sufficiently allowed so as to appear in both electronic absorption and emission.

  2. Romanian government bond market

    Directory of Open Access Journals (Sweden)

    Cornelia POP

    2012-12-01

    Full Text Available The present paper aims to present the level of development reached by Romanian government bond market segment, as part of the country financial market. The analysis will be descriptive (the data series available for Romania are short, based on the secondary data offered by the official bodies involved in the process of issuing and trading the Romanian government bonds (Romanian Ministry of Public Finance, Romanian National Bank and Bucharest Stock Exchange, and also on secondary data provided by the Federation of European Stock Exchanges.To enhance the market credibility as a benchmark, a various combination of measures is necessary; among these measures are mentioned: the extension of the yield curve; the issuance calendars in order to improve transparency; increasing the disclosure of information on public debt issuance and statistics; holding regular meetings with dealers, institutional investors and rating agencies; introducing a system of primary dealers; establishing a repurchase (repo market in the government bond market. These measures will be discussed based on the evolution presented inside the paper.The paper conclude with the fact that, until now, the Romanian government bond market did not provide a benchmark for the domestic financial market and that further efforts are needed in order to increase the government bond market transparency and liquidity.

  3. Safe and Liquid Mortgage Bonds

    DEFF Research Database (Denmark)

    Dick-Nielsen, Jens; Gyntelberg, Jacob; Lund, Jesper

    This paper shows that strict match pass-through funding of covered bonds provides safe and liquid mortgage bonds. Despite a 30% drop in house prices during the 2008 global crisis Danish mortgage bonds remained as liquid as most European government bonds. The Danish pass-through system effectively...... eliminates credit risk from the investor's perspective. Similar to other safe bonds, funding liquidity becomes the main driver of mortgage bond liquidity and this creates commonality in liquidity across markets and countries. These findings have implications for how to design a robust mortgage bond system...

  4. Safe and Liquid Mortgage Bonds

    DEFF Research Database (Denmark)

    Dick-Nielsen, Jens; Gyntelberg, Jacob; Lund, Jesper

    This paper shows that strict match pass-through funding of covered bonds provides safe and liquid mortgage bonds. Despite a 30% drop in house prices during the 2008 global crisis Danish mortgage bonds remained as liquid as most European government bonds. The Danish pass-through system effectively...... eliminates credit risk from the investor's perspective. Similar to other safe bonds, funding liquidity becomes the main driver of mortgage bond liquidity and this creates commonality in liquidity across markets and countries. These findings have implications for how to design a robust mortgage bond system...

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

    Science.gov (United States)

    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. FETAL FOOT LENGTH AND HAND LENGTH: RELATIONSHIP WITH CROWN RUMP LENGTH AND GESTATIONAL AGE

    Directory of Open Access Journals (Sweden)

    Garima

    2015-12-01

    Full Text Available BACKGROUND Estimation of gestational age of fetus is of great medicolegal importance. Multiple parameters of the fetal anatomical measurements are in use. However, gestational age assessment may be difficult in fetus with anencephaly, hydrocephalus, short limb dysplasia, post mortem destruction or in mutilated case. Study of literature suggests that fetal foot has a characteristic pattern of normal growth and the fetal foot shows gradual increase in length relative to the length of the embryo and could be used to estimate gestational age. The purpose of the present study is to determine the accuracy in estimating gestational age using fetal foot and hand length by studying its relation with crown rump length in the foetuses of Manipuri origin. AIMS AND OBJECTIVES 1 To study the relationship between fetal crown rump length and fetal hand and foot length, thereby determining the accuracy in estimating gestational age by a cross-sectional study. MATERIALS AND METHODS A total of 100 formalin fixed fetuses of Manipuri origin, obtained from the Department of Obstetrics and Gynaecology, Regional Institute of Medical Sciences, Imphal, were included in the study, carried out in the Department of Anatomy, from February 2015 to July 2015. The parameters studied were crown rump length, foot length and hand length of fetuses. The data was analysed using SPSS software by regression analysis. Graphs were also plotted to determine pattern of growth and their correlation with crown rump length if any. RESULTS A total of 100 fetuses were studied, of which 43 were females and 57 were males. The mean foot length and hand length progressively increased with increase in crown rump length. Measurements were not significantly different in right or left side or among male and female fetuses. A statistically significant linear relationship was seen between foot length and crown rump length of the fetus (r=0.980, p<0.0001 and hand length and crown rump length of the fetus

  7. The Trouble With Bonds

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ In early June,global financial markets gyrated downwards in the wake of central banks'tough language on inflation.At one point bond prices reflected expectations of four rate hikes by the US Federal Reserve (Fed) in the next 12 months.As a result,the dollar firmed,oil prices stabilized,and yield curves flattened around the world.If all these inflation-fighting measures are real,the situation bodes well for bonds.But,I think otherwise.

  8. Anodic bonded graphene

    Science.gov (United States)

    Balan, Adrian; Kumar, Rakesh; Boukhicha, Mohamed; Beyssac, Olivier; Bouillard, Jean-Claude; Taverna, Dario; Sacks, William; Marangolo, Massimiliano; Lacaze, Emanuelle; Gohler, Roger; Escoffier, Walter; Poumirol, Jean-Marie; Shukla, Abhay

    2010-09-01

    We show how to prepare graphene samples on a glass substrate with the anodic bonding method. In this method, a graphite precursor in flake form is bonded to a glass substrate with the help of an electrostatic field and then cleaved off to leave few layer graphene on the substrate. Now that several methods are available for producing graphene, the relevance of our method is in its simplicity and practicality for producing graphene samples of about 100 µm lateral dimensions. This method is also extensible to other layered materials. We discuss some detailed aspects of the fabrication and results from Raman spectroscopy, local probe microscopy and transport measurements on these samples.

  9. Anodic bonded graphene

    Energy Technology Data Exchange (ETDEWEB)

    Balan, Adrian; Kumar, Rakesh; Boukhicha, Mohamed; Beyssac, Olivier; Bouillard, Jean-Claude; Taverna, Dario; Sacks, William; Shukla, Abhay [Universite Pierre et Marie Curie-Paris 6, CNRS-UMR7590, Institut de Mineralogie et de Physique des Milieux Condenses, 140 rue de Lourmel, Paris, F-75015 France (France); Marangolo, Massimiliano; Lacaze, Emanuelle; Gohler, Roger [Universite Pierre et Marie Curie-Paris 6, CNRS-UMR7588, Institut des Nanosciences de Paris, 140 rue de Lourmel, Paris, F-75015 France (France); Escoffier, Walter; Poumirol, Jean-Marie, E-mail: abhay.shukla@upmc.f [Laboratoire National des Champs Magnetiques Intenses, INSA UPS CNRS, UPR 3228, Universite de Toulouse, 143 avenue de Rangueil, 31400 Toulouse (France)

    2010-09-22

    We show how to prepare graphene samples on a glass substrate with the anodic bonding method. In this method, a graphite precursor in flake form is bonded to a glass substrate with the help of an electrostatic field and then cleaved off to leave few layer graphene on the substrate. Now that several methods are available for producing graphene, the relevance of our method is in its simplicity and practicality for producing graphene samples of about 100 {mu}m lateral dimensions. This method is also extensible to other layered materials. We discuss some detailed aspects of the fabrication and results from Raman spectroscopy, local probe microscopy and transport measurements on these samples.

  10. Hydrogen bonded supramolecular materials

    CERN Document Server

    Li, Zhan-Ting

    2015-01-01

    This book is an up-to-date text covering topics in utilizing hydrogen bonding for constructing functional architectures and supramolecular materials. The first chapter addresses the control of photo-induced electron and energy transfer. The second chapter summarizes the formation of nano-porous materials. The following two chapters introduce self-assembled gels, many of which exhibit unique functions. Other chapters cover the advances in supramolecular liquid crystals and the versatility of hydrogen bonding in tuning/improving the properties and performance of materials. This book is designed

  11. Cooperativity in beryllium bonds.

    Science.gov (United States)

    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.

  12. Hydrogen bond and halogen bond inside the carbon nanotube

    Science.gov (United States)

    Wang, Weizhou; Wang, Donglai; Zhang, Yu; Ji, Baoming; Tian, Anmin

    2011-02-01

    The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated.

  13. Short Carboxylic Acid–Carboxylate Hydrogen Bonds Can Have Fully Localized Protons

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jiusheng; Pozharski, Edwin; Wilson, Mark A.

    2017-01-17

    Short hydrogen bonds (H-bonds) have been proposed to play key functional roles in several proteins. The location of the proton in short H-bonds is of central importance, as proton delocalization is a defining feature of low-barrier hydrogen bonds (LBHBs). Experimentally determining proton location in H-bonds is challenging. Here, bond length analysis of atomic (1.15–0.98 Å) resolution X-ray crystal structures of the human protein DJ-1 and its bacterial homologue, YajL, was used to determine the protonation states of H-bonded carboxylic acids. DJ-1 contains a buried, dimer-spanning 2.49 Å H-bond between Glu15 and Asp24 that satisfies standard donor–acceptor distance criteria for a LBHB. Bond length analysis indicates that the proton is localized on Asp24, excluding a LBHB at this location. However, similar analysis of the Escherichia coli homologue YajL shows both residues may be protonated at the H-bonded oxygen atoms, potentially consistent with a LBHB. A Protein Data Bank-wide screen identifies candidate carboxylic acid H-bonds in approximately 14% of proteins, which are typically short [O–O> = 2.542(2) Å]. Chemically similar H-bonds between hydroxylated residues (Ser/Thr/Tyr) and carboxylates show a trend of lengthening O–O distance with increasing H-bond donor pKa. This trend suggests that conventional electronic effects provide an adequate explanation for short, charge-assisted carboxylic acid–carboxylate H-bonds in proteins, without the need to invoke LBHBs in general. This study demonstrates that bond length analysis of atomic resolution X-ray crystal structures provides a useful experimental test of certain candidate LBHBs.

  14. Evaluation of enamel damages following orthodontic bracket debonding in fluorosed teeth bonded with adhesion promoter.

    Science.gov (United States)

    Baherimoghadam, Tahreh; Akbarian, Sahar; Rasouli, Reza; Naseri, Navid

    2016-01-01

    To evaluate shear bond strength (SBS) of the orthodontic brackets bonded to fluorosed and nonfluorosed teeth using Light Bond with and without adhesion promoters and compare their enamel damages following debonding. In this study, 30 fluorosed (Thylstrup and Fejerskov Index = 4-5) and 30 nonfluorosed teeth were randomly distributed between two subgroups according to the bonding materials: Group 1, fluorosed teeth bonded with Light Bond; Group 2, fluorosed teeth bonded with adhesion promoters and Light Bond; Group 3, nonfluorosed teeth bonded with Light Bond; Group 4, nonfluorosed bonded with adhesion promoters and Light Bond. After bonding, the SBS of the brackets was tested with a universal testing machine. Stereomicroscopic evaluation was performed by unbiased stereology in all teeth to determine the amount of adhesive remnants and the number and length of enamel cracks before bonding and after debonding. The data were analyzed using two-way analysis of variance, Kruskal-Wallis, Wilcoxon Signed Rank, and Mann-Whitney test. While fluorosis reduced the SBS of orthodontic bracket (P = 0.017), Enhance Locus Ceruleus LC significantly increased the SBS of the orthodontic bracket in fluorosed and nonfluorosed teeth (P = 0.039). Significant increasing in the number and length of enamel crack after debonding was found in all four groups. There were no significant differences in the length of enamel crack increased after debonding among four groups (P = 0.768) while increasing in the number of enamel cracks after debonding was significantly different among the four groups (P = 0.023). Teeth in Group 2 showed the highest enamel damages among four groups following debonding. Adhesion promoters could improve the bond strength of orthodontic brackets, but conservative debonding methods for decreasing enamel damages would be necessary.

  15. Evaluation of enamel damages following orthodontic bracket debonding in fluorosed teeth bonded with adhesion promoter

    Science.gov (United States)

    Baherimoghadam, Tahreh; Akbarian, Sahar; Rasouli, Reza; Naseri, Navid

    2016-01-01

    Objective: To evaluate shear bond strength (SBS) of the orthodontic brackets bonded to fluorosed and nonfluorosed teeth using Light Bond with and without adhesion promoters and compare their enamel damages following debonding. Materials and Methods: In this study, 30 fluorosed (Thylstrup and Fejerskov Index = 4–5) and 30 nonfluorosed teeth were randomly distributed between two subgroups according to the bonding materials: Group 1, fluorosed teeth bonded with Light Bond; Group 2, fluorosed teeth bonded with adhesion promoters and Light Bond; Group 3, nonfluorosed teeth bonded with Light Bond; Group 4, nonfluorosed bonded with adhesion promoters and Light Bond. After bonding, the SBS of the brackets was tested with a universal testing machine. Stereomicroscopic evaluation was performed by unbiased stereology in all teeth to determine the amount of adhesive remnants and the number and length of enamel cracks before bonding and after debonding. The data were analyzed using two-way analysis of variance, Kruskal–Wallis, Wilcoxon Signed Rank, and Mann–Whitney test. Results: While fluorosis reduced the SBS of orthodontic bracket (P = 0.017), Enhance Locus Ceruleus LC significantly increased the SBS of the orthodontic bracket in fluorosed and nonfluorosed teeth (P = 0.039). Significant increasing in the number and length of enamel crack after debonding was found in all four groups. There were no significant differences in the length of enamel crack increased after debonding among four groups (P = 0.768) while increasing in the number of enamel cracks after debonding was significantly different among the four groups (P = 0.023). Teeth in Group 2 showed the highest enamel damages among four groups following debonding. Conclusion: Adhesion promoters could improve the bond strength of orthodontic brackets, but conservative debonding methods for decreasing enamel damages would be necessary. PMID:27095895

  16. Using Excel To Study The Relation Between Protein Dihedral Angle Omega And Backbone Length

    Science.gov (United States)

    Shew, Christopher; Evans, Samari; Tao, Xiuping

    How to involve the uninitiated undergraduate students in computational biophysics research? We made use of Microsoft Excel to carry out calculations of bond lengths, bond angles and dihedral angles of proteins. Specifically, we studied protein backbone dihedral angle omega by examining how its distribution varies with the length of the backbone length. It turns out Excel is a respectable tool for this task. An ordinary current-day desktop or laptop can handle the calculations for midsized proteins in just seconds. Care has to be taken to enter the formulas for the spreadsheet column after column to minimize the computing load. Supported in part by NSF Grant #1238795.

  17. IMPEDANCE OF FINITE LENGTH RESISTOR

    Energy Technology Data Exchange (ETDEWEB)

    KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.

    2005-05-15

    We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.

  18. Bond Tension in Tethered Macromolecules.

    Science.gov (United States)

    Sheiko, Sergei S; Panyukov, Sergey; Rubinstein, Michael

    2011-06-14

    The paper presents scaling analysis of mechanical tension generated in densely branched macromolecules tethered to a solid substrate with a short linker. Steric repulsion between branches results in z-fold amplification of tension in the linker, where z is the number of chain-like arms. At large z ~ 100-1000, the generated tension may exceed the strength of covalent bonds and sever the linker. Two types of molecular architectures were considered: polymer stars and polymer "bottlebrushes" tethered to a solid substrate. Depending on the grafting density, one distinguishes the so-called mushroom, loose grafting, and dense grafting regimes. In isolated (mushroom) and loosely tethered bottlebrushes, the linker tension is by a factor of [Formula: see text] smaller than the tension in a tethered star with the same number of arms z. In densely tethered stars, the effect of interchain distance (d) and number of arms (z) on the magnitude of linker tension is given by f ≅ f0z(3/2)(b/d) for stars in a solvent environment and f ≅ f0z(2) (b/d)(2) for dry stars, where b is the Kuhn length and f0 ≅ kBT/b is intrinsic bond tension. These relations are also valid for tethered bottlebrushes with long side chains. However, unlike molecular stars, bottlebrushes demonstrate variation of tension along the backbone f ≅ f0s z(1/2) / d as a function of distance s from the free end of the backbone. In dense brushes [Formula: see text] with z ≅ 1000, the backbone tension increases from f ≅ f0 = 1 pN at the free end of the backbone (s ≅ b) to its maximum f ≅ zf0 ≅ 1 nN at the linker to the substrate (s ≅ zb).

  19. Similarities between intra- and intermolecular hydrogen bonds in RNA kissing complexes found by means of cross-correlated relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Dittmer, Jens [Institut de Chimie Moleculaire et Biologique, Ecole Polytechnique Federale de Lausanne, BCH (Switzerland); Kim, Chul-Hyun [University of California, Department of Chemistry (United States); Bodenhausen, Geoffrey [Institut de Chimie Moleculaire et Biologique, Ecole Polytechnique Federale de Lausanne, BCH (Switzerland)], E-mail: Geoffrey.Bodenhausen@ens.fr

    2003-07-15

    The bond lengths and dynamics of intra- and intermolecular hydrogen bonds in an RNA kissing complex have been characterized by determining the NMR relaxation rates of various double- and triple-quantum coherences that involve an imino proton and two neighboring nitrogen-15 nuclei belonging to opposite bases. New experiments allow one to determine the chemical shift anisotropy of the imino protons. The bond lengths derived from dipolar relaxation and the lack of modulations of the nitrogen chemical shifts indicate that the intermolecular hydrogen bonds which hold the kissing complex together are very similar to the intramolecular hydrogen bonds in the double-stranded stem of the RNA.

  20. Polyketide chain length control by chain length factor.

    Science.gov (United States)

    Tang, Yi; Tsai, Shiou-Chuan; Khosla, Chaitan

    2003-10-22

    Bacterial aromatic polyketides are pharmacologically important natural products. A critical parameter that dictates product structure is the carbon chain length of the polyketide backbone. Systematic manipulation of polyketide chain length represents a major unmet challenge in natural product biosynthesis. Polyketide chain elongation is catalyzed by a heterodimeric ketosynthase. In contrast to homodimeric ketosynthases found in fatty acid synthases, the active site cysteine is absent from the one subunit of this heterodimer. The precise role of this catalytically silent subunit has been debated over the past decade. We demonstrate here that this subunit is the primary determinant of polyketide chain length, thereby validating its designation as chain length factor. Using structure-based mutagenesis, we identified key residues in the chain length factor that could be manipulated to convert an octaketide synthase into a decaketide synthase and vice versa. These results should lead to novel strategies for the engineered biosynthesis of hitherto unidentified polyketide scaffolds.

  1. Curve Length Estimation using Vertix Chain Code Curve Length Estimation

    Directory of Open Access Journals (Sweden)

    Habibollah Haron

    2010-09-01

    Full Text Available Most of the applications in image analysis are based on Freeman chain code. In this paper, for the first time, vertex chain code (VCC proposed by Bribiesca is applied to improve length estimation of the 2D digitized curve. The chain code has some preferences such as stable in shifting, turning, mirroring movement of image and has normalized starting point. Due to the variety of length estimator methods, we focused on the three specific techniques. First, the way Bribiesca proposed which is based on counting links between vertices; second, based on maximum length digital straight segments (DSSs and lastly local metrics. The results of these length estimators with the real perimeter are compared. Results thus obtained exhibits thatlength estimation using VCC is nearest to the actual length.

  2. Shear bond strength of the Tenure Solution dentin bonding system.

    Science.gov (United States)

    Barkmeier, W W; Cooley, R L

    1989-10-01

    A liquid solution of an oxalate bonding system containing NTG-GMA and PMDM has become commercially available. The bond strength of this oxalate adhesive (Tenure Solution) to dentin was determined by bonding composite resin cylinders to extracted teeth. The bond strengths obtained in this study are compared to the bond strengths obtained in earlier studies with the first and second generation oxalate adhesives whose components were supplied as powders and required mixing. The oxalate solutions developed significantly higher bond strengths than the original powder type systems.

  3. Bonding in cementitious composites

    Energy Technology Data Exchange (ETDEWEB)

    Mindess, S. (British Columbia Univ., Vancouver, BC (Canada)) Shah, S.P. (Northwestern Univ., Evanston, IL (USA))

    1988-01-01

    These proceedings discuss the papers presented at the symposium on the subject of high performance cement composites. Some of the topics discussed were; calcium hydroxides treated ceramics microspheres and mechanical properties of high temperature light weight cements; microstructure and chemical variations of class F fly ash; microstructure and bond strength of cement and crack propagation as detected by laser holography and acoustic emission.

  4. Photochemical tissue bonding

    Science.gov (United States)

    Redmond, Robert W.; Kochevar, Irene E.

    2012-01-10

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

  5. Thermal Bond System.

    Science.gov (United States)

    1995-10-31

    a twill weave, a crowfoot weave, a satin weave (FIG. 2), and a leno weave. Descriptions of the various weave types can be found in " Composite ...together to define a fabric mesh having first and second opposing woven surfaces. An adhesive bond that is flowable prior to drying is used to wet and

  6. The quantum nature of the hydrogen bond: insight from path-integral molecular dynamics

    Science.gov (United States)

    Walker, Brent; Li, Xin-Zheng; Michaelides, Angelos

    2011-03-01

    Hydrogen (H) bonds are weak, generally intermolecular bonds, that hold together much of soft matter, the condensed phases of water, network liquids, and many ferroelectric crystals. The small mass of H means H-bonds are inherently quantum mechanical; effects such as zero point motion and tunneling should be considered, although often are not. In particular, a consistent picture of quantum nuclear effects on the strength of H-bonds and consequently the structure of H-bonded systems is still absent. Here, we report ab initio path-integral molecular dynamics studies on the quantum nature of the H-bond. Systematic examination of a range of H-bonded systems shows that quantum nuclei weaken weak H-bonds but strengthen relatively strong ones. This correlation arises from a competition between anharmonic intermolecular bond bending and intramolecular bond stretching. A simple rule of thumb enables predictions to be made for H-bonded bonded materials in general with merely classical knowledge (e.g. H-bond strength or H-bond length). Our work rationalizes the contrasting influence of quantum nuclear dynamics on a wide variety of materials, including liquid water and HF, and highlights the need for flexible molecules in force-field based studies of quantum nuclear dynamics.

  7. Unified description of hydrogen bonding by a two-state effective Hamiltonian

    CERN Document Server

    McKenzie, Ross H

    2011-01-01

    An effective Hamiltonian is considered for hydrogen bonding between two molecules due to the quantum mechanical interaction between the orbitals of the H-atom and the donor and acceptor atoms in the molecules. The Hamiltonian acts on two diabatic states and has a simple chemically motivated form for its matrix elements. The model gives insight into the "H-bond puzzle", describes different classes of bonds, and empirical correlations between the donor-acceptor distance $R$ and binding energies, bond lengths, and the softening of vibrational frequencies. A key prediction is the UV photo-dissociation of H-bonded complexes via an excited electronic state with an exalted vibrational frequency.

  8. Impedance of Finite Length Resistor

    CERN Document Server

    Krinsky, Samuel; Podobedov, Boris

    2005-01-01

    We determine the impedance of a cylindrical metal tube (resistor) of radius a and length g, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the behavior of the impedance at high frequency (k>>1/a). In the equilibrium regime, ka2

  9. Line Lengths and Starch Scores.

    Science.gov (United States)

    Moriarty, Sandra E.

    1986-01-01

    Investigates readability of different line lengths in advertising body copy, hypothesizing a normal curve with lower scores for shorter and longer lines, and scores above the mean for lines in the middle of the distribution. Finds support for lower scores for short lines and some evidence of two optimum line lengths rather than one. (SKC)

  10. Gestation length in farmed reindeer.

    Science.gov (United States)

    Shipka, M P; Rowell, J E

    2010-01-01

    Reindeer (Rangifer tarandus tarundus) are the only cervids indigenous to the arctic environment. In Alaska, reindeer are a recognized agricultural species and an economic mainstay for many native populations. Traditionally raised in extensive free-ranging systems, a recent trend toward intensive farming requires a more in-depth knowledge of reproductive management. Reported gestation length in reindeer varies, ranging from 198 to 229 d in studies performed at the University of Alaska Fairbanks. A switchback study that manipulated only breeding date demonstrated a mean increase in gestation length of 8.5 d among females bred early in the season. The negative correlation between conception date and gestation length is consistent with reindeer research at other locations and reports of variable gestation length in a growing number of domestic and non-domestic species. This paper reviews the phenomenon in reindeer and discusses some of the factors known to affect gestation length as well as possible areas for future research.

  11. Reserved-Length Prefix Coding

    CERN Document Server

    Baer, Michael B

    2008-01-01

    Huffman coding finds an optimal prefix code for a given probability mass function. Consider situations in which one wishes to find an optimal code with the restriction that all codewords have lengths that lie in a user-specified set of lengths (or, equivalently, no codewords have lengths that lie in a complementary set). This paper introduces a polynomial-time dynamic programming algorithm that finds optimal codes for this reserved-length prefix coding problem. This has applications to quickly encoding and decoding lossless codes. In addition, one modification of the approach solves any quasiarithmetic prefix coding problem, while another finds optimal codes restricted to the set of codes with g codeword lengths for user-specified g (e.g., g=2).

  12. Novel approach to the concept of bond-valence vectors.

    Science.gov (United States)

    Zachara, Janusz

    2007-11-12

    A new approach to the old idea of deriving a bond-valence vector from the well-known bond-valence concept has been proposed. The foundation of the proposal is the previous electrostatic model in which bond valences are interpreted as electric fluxes. The outcome of this approach is actual vectorial quantities whose magnitudes are strictly but nonlinearly related to the scalar bond valences and are directed along the bond lines. It has been proved that the sum of all these bond-valence vectors drawn from a coordination center to its ligating atoms will be close to zero for the complete coordination sphere. Therefore, unlike the scalar bond valences, the obtained vectors provide information about the spatial arrangement of ligands. The geometrical consequences of the proposed bond-valence vector (BVV) model are analyzed for the geometries of the carbonates, phosphates, and five-coordinated organoaluminum compounds with CO3, PO4, and AlCO4 skeletons, respectively, retrieved from the Cambridge Structural Database. For acyclic carbonates this BVV model allows one to predict the O-C-O angles with a mean absolute error of 1.0 degrees using the empirical C-O distances only. Furthermore, this BVV model is able to quantitatively describe the strains in cyclic carbonates. The preliminary studies for NO2E, PO3E, and SO3E systems with a strongly stereoactive lone electron pair (E) show that the model may serve as a quantitative description of the lone electron pair effect on the coordination sphere. A great advantage of the presented BVV approach is that the derived relation between a bond-valence vector, bond valence, and bond length is given by an uncomplicated equation allowing quick and simple computations, thus providing a new analytical tool for describing the geometry of a coordination sphere that may be applied for structure validation.

  13. Trading in Treasury Bond Futures Contracts and Bonds in Australia

    OpenAIRE

    Belinda Cheung

    2014-01-01

    Treasury bond futures are a key financial product in Australia, with turnover in Treasury bond futures contracts significantly larger than turnover in the market for Commonwealth Government securities (CGS). Treasury bond futures contracts provide a wide variety of market participants with the ability to hedge against, or gain exposure to, interest rate risk. This article discusses some of the features of the Treasury bond futures contract, and how the contract is used to facilitate hedging a...

  14. Distribution of Stress on Bonded Length of Tension-type Rock Bolt Based on Theory of Elasticity%基于弹性理论的拉力型锚杆锚固段应力分布规律研究

    Institute of Scientific and Technical Information of China (English)

    彭辉; 袁超; 向德强

    2013-01-01

    视锚杆和周围介质为弹性材料,在弹性半空间里,利用Mindlin位移解,根据拉力型锚杆实际工作状态,推导出拉力型锚杆锚固段轴向应力和弹性粘结应力分布的方程。并分析相关岩土参数对锚固段轴向应力和剪应力的分布的影响,得出影响较大的几个因素,为拉力杆的力学分析和工程设计提供理论依据。%This research provides a theoretical basis for the pull rod mechanics analysis and en-gineering design. In accordance with the above,we can analyse related geotechnical parameters on the axial stress and shear stress distribution of the anchorage segment,and influence of sev-eral factors can be concluded. According to tensile type anchor rod under the actual working condition,we can deduce the equation about the distribution of axial stress and elastic bond stress of tensile type anchor's anchoring section when the anchor bolt and the surrounding me-dium are elastic materials by Mindlin's displacement solution in elastic half-space.

  15. Indirect bonding technique in orthodontics

    Directory of Open Access Journals (Sweden)

    Kübra Yıldırım

    2016-08-01

    Full Text Available ‘Direct Bonding Technique’ which allows the fixed orthodontic appliances to be directly bonded to teeth without using bands decreased the clinic time for bracket bonding and increased esthetics and oral hygiene during orthodontic treatment. However, mistakes in bracket positioning were observed due to decreased direct visual sight and access to posterior teeth. ‘Indirect Bonding Technique’ was developed for eliminating these problems. Initially, decreased bond strength, higher bond failure rate, periodontal tissue irritation, compromised oral hygiene and increased laboratory time were the main disadvantages of this technique when compared to direct bonding. The newly developed materials and modified techniques help to eliminate these negative consequences. Today, the brackets bonded with indirect technique have similar bond strength with brackets bonded directly. Moreover, indirect and direct bonding techniques have similar effects on periodontal tissues. However, indirect bonding technique requires more attention and precision in laboratory and clinical stage, and has higher cost. Orthodontist's preference between these two bonding techniques may differ according to time spent in laboratory and clinic, cost, patient comfort and personal opinion.

  16. Wafer bonding using Cu-Sn intermetallic bonding layers

    NARCIS (Netherlands)

    Flötgen, C.; Pawlak, M.; Pabo, E.; Wiel, H.J. van de; Hayes, G.R.; Dragoi, V.

    2014-01-01

    Wafer-level Cu-Sn intermetallic bonding is an interesting process for advanced applications in the area of MEMS and 3D interconnects. The existence of two intermetallic phases for Cu-Sn system makes the wafer bonding process challenging. The impact of process parameters on final bonding layer

  17. Thioamides: versatile bonds to induce directional and cooperative hydrogen bonding in supramolecular polymers.

    Science.gov (United States)

    Mes, Tristan; Cantekin, Seda; Balkenende, Dirk W R; Frissen, Martijn M M; Gillissen, Martijn A J; De Waal, Bas F M; Voets, Ilja K; Meijer, E W; Palmans, Anja R A

    2013-06-24

    The amide bond is a versatile functional group and its directional hydrogen-bonding capabilities are widely applied in, for example, supramolecular chemistry. The potential of the thioamide bond, in contrast, is virtually unexplored as a structuring moiety in hydrogen-bonding-based self-assembling systems. We report herein the synthesis and characterisation of a new self-assembling motif comprising thioamides to induce directional hydrogen bonding. N,N',N''-Trialkylbenzene-1,3,5-tris(carbothioamide)s (thioBTAs) with either achiral or chiral side-chains have been readily obtained by treating their amide-based precursors with P2S5. The thioBTAs showed thermotropic liquid crystalline behaviour and a columnar mesophase was assigned. IR spectroscopy revealed that strong, three-fold, intermolecular hydrogen-bonding interactions stabilise the columnar structures. In apolar alkane solutions, thioBTAs self-assemble into one-dimensional, helical supramolecular polymers stabilised by three-fold hydrogen bonding. Concentration- and temperature-dependent self-assembly studies performed by using a combination of UV and CD spectroscopy demonstrated a cooperative supramolecular polymerisation mechanism and a strong amplification of supramolecular chirality. The high dipole moment of the thioamide bond in combination with the anisotropic shape of the resulting cylindrical aggregate gives rise to sufficiently strong depolarised light scattering to enable depolarised dynamic light scattering (DDLS) experiments in dilute alkane solution. The rotational and translational diffusion coefficients, D(trans) and D(rot), were obtained from the DDLS measurements, and the average length, L, and diameter, d, of the thioBTA aggregates were derived (L = 490 nm and d = 3.6 nm). These measured values are in good agreement with the value L(w) = 755 nm obtained from fitting the temperature-dependent CD data by using a recently developed equilibrium model. This experimental verification

  18. Minimum length-maximum velocity

    Science.gov (United States)

    Panes, Boris

    2012-03-01

    We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example, we can predict the ratio between the minimum lengths in space and time using the results from OPERA on superluminal neutrinos.

  19. China-Russia Bond

    Institute of Scientific and Technical Information of China (English)

    Ji Zhiye; Ma Zongshi

    2007-01-01

    @@ Thanks to China's successful launching of the Year of Russia, 2006 will surely go down as a milestone in the history of the China-Russia bond. Furthermore, a still-warmer climate will continue to prevail in 2007 when Moscow, in its turn, hosts the Year of China, trying to outshine its next-door neighbor in this regard, as Russian President Vladimir Putin promised in the exchange of new year greetings with his Chinese counterpart, President Hu Jintao.

  20. Direct bonded space maintainers.

    Science.gov (United States)

    Santos, V L; Almeida, M A; Mello, H S; Keith, O

    1993-01-01

    The aim of this study was to evaluate clinically a bonded space maintainer, which would reduce chair-side time and cost. Sixty appliances were fabricated from 0.7 mm stainless steel round wire and bonded using light-cured composite to the two teeth adjacent to the site of extraction of a posterior primary tooth. Twenty males and sixteen females (age range 5-9-years-old) were selected from the Pedodontic clinic of the State University of Rio de Janeiro. The sixty space maintainers were divided into two groups according to the site in which they were placed: a) absent first primary molar and b) absent second primary molar. Impressions and study models were obtained prior to and 6 months after bonding the appliances. During this period only 8.3% of failures were observed, most of them from occlusal or facial trauma. Student t-test did not show statistically significant alterations in the sizes of the maintained spaces during the trial period.

  1. Coulombic Models in Chemical Bonding.

    Science.gov (United States)

    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)

  2. Optimal Investment in Structured Bonds

    DEFF Research Database (Denmark)

    Jessen, Pernille; Jørgensen, Peter Løchte

    The paper examines the role of structured bonds in the optimal portfolio of a small retail investor. We consider the typical structured bond essentially repacking an exotic option and a zero coupon bond, i.e. an investment with portfolio insurance. The optimal portfolio is found when the investment...

  3. Mittal bonded tongue thrusting appliance

    Directory of Open Access Journals (Sweden)

    Rekha Mittal

    2014-01-01

    Full Text Available These days majority of orthodontist includes bonded molar attachment in their inventory to eliminate the discomfort of molar separation during initial appointment and band spaces left at the end of treatment. This article describes a innovative and economical method of attachment of bonded tongue crib if required during the initial or later stages of treatment along with bonded molar tubes.

  4. Influence of metal bonding layer on strain transfer performance of FBG

    Science.gov (United States)

    Liu, Hao; Chen, Weimin; Zhang, Peng; Liu, Li; Shu, Yuejie; Wu, Jun

    2013-01-01

    Metal bonding layer seriously affects the strain transfer performance of Fiber Bragg Grating (FBG). Based on the mode of FBG strain transfer, the influence of the length, the thickness, Poisson's ratio, elasticity modulus of metal bonding layer on the strain transfer coefficient of FBG is analyzed by numerical simulation. FBG is packaged to steel wire using metal bonding technology of FBG. The tensile tests of different bonding lengths and elasticity modulus are carried out. The result shows the strain transfer coefficient of FBGs are 0.9848,0.962 and their average strain sensitivities are 1.076 pm/μɛ,1.099 pm/μɛ when the metal bonding layer is zinc, whose lengths are 15mm, 20mm, respectively. The strain transfer coefficient of FBG packaged by metal bonding layer raises 8.9 percent compared to epoxy glue package. The preliminary experimental results show that the strain transfer coefficient increases with the length of metal bonding layer, decreases with the thickness of metal bonding layer and the influence of Poisson's ratio can be ignored. The experiment result is general agreement with the analysis and provides guidance for metal package of FBG.

  5. On the bonding and the electric field gradient of the uranyl ion

    NARCIS (Netherlands)

    de Jong, WA; Visscher, L; Nieuwpoort, WC

    1999-01-01

    Molecular properties of the uranyl ion ([UO2](2+)) are studied using both a non-relativistic and a relativistic method. Inclusion of relativity leads to a bond length expansion and makes the electric field gradient (EFG) at the uranium nucleus strongly dependent on the U-O bond distance, The non-rel

  6. Novel Position-Space Renormalization Group for Bond Directed Percolation in Two Dimensions

    OpenAIRE

    KAYA, H.; Erzan, A.

    1998-01-01

    A new position-space renormalization group approach is investigated for bond directed percolation in two dimensions. The threshold value for the bond occupation probabilities is found to be $p_c=0.6443$. Correlation length exponents on time (parallel) and space (transverse) directions are found to be $\

  7. Pairing versus quarteting coherence length

    CERN Document Server

    Delion, Doru S

    2015-01-01

    We systematically analyse the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have in all considered cases a long range character inside the nucleus and decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in continuum is investigated. Strong shell effects are evidenced, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar...

  8. Length Invisibilization of Tachyonic Neutrinos

    Science.gov (United States)

    Estakhr, Ahmad Reza

    2016-09-01

    Faster than the speed of light particle such as tachyonic neutrino due to its superluminal nature disapper and is undetectable. L = iΩ-1Lo where, i =√{ - 1 } is imaginary Number, Ω = 1 /√{βs2 - 1 } is Estakhr's Omega factor, L is the Superluminal Length, Lo is the proper length, βs =Vs / c > 1 is superluminal speed parameter, Vs is Superluminal velocity and c is speed of light.

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

    National Research Council Canada - National Science Library

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

    2009-01-01

    .... A 30-mm-length double-end diffusion-bonded Nd:YVO(4) crystal was utilized for efficient self-Raman laser operation by reducing the thermal effects and increasing the interaction length for the stimulated Raman scattering...

  10. Efficient second harmonic generation of double-end diffusion-bonded Nd:YVO_4 self-Raman laser producing 7.9 W yellow light

    National Research Council Canada - National Science Library

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

    2009-01-01

    .... A 30-mm-length double-end diffusion-bonded Nd:YVO_4 crystal was utilized for efficient self-Raman laser operation by reducing the thermal effects and increasing the interaction length for the stimulated Raman scattering...

  11. Nanoleakage of cervical restorations of four dentin bonding systems.

    Science.gov (United States)

    Li, H; Burrow, M F; Tyas, M J

    2000-01-01

    The aim of this study was to evaluate the degree of nanoleakage of restorations placed in cervical preparations with dentin bonding systems. The dentin bonding systems used were Single Bond, One Coat Bond, Prime & Bond NT/NRC, and PermaQuik. Ten saucer-shaped cervical preparations were bonded with one of the dentin bonding systems and restored with Silux Plus resin composite in each group. After 24 hours storage in 37 degrees C water, restorations were finished and the surrounding tooth surfaces were coated with nail varnish. The samples were immersed in 50% w/v solution of silver nitrate for 24 hours, and exposed to photodeveloping solution for 8 hours. The samples were cut longitudinally through the center, polished, carbon coated and observed in a Field Emission SEM using backscattered electron mode. The degree of silver penetration along the preparation wall was observed and calculated as a percentage of the total preparation wall length. Results were analyzed by one-way ANOVA and LSD tests. PermaQuik demonstrated the lowest leakage score and the least silver deposition within the hybrid layer, while Prime & Bond NT/NRC showed the greatest leakage scores and the most silver deposition within the hybrid layer. Different nanoleakage patterns were observed for the different adhesive systems. First, the composition of each adhesive system may play a role in the different leakage patterns. Second, the current dentin bonding systems used in this study did not achieve perfect sealing at the restoration-dentin interface. This may influence the durability of the bond to dentin.

  12. Optimal Investment in Structured Bonds

    DEFF Research Database (Denmark)

    Jessen, Pernille; Jørgensen, Peter Løchte

    The paper examines the role of structured bonds in the optimal portfolio of a small retail investor. We consider the typical structured bond essentially repacking an exotic option and a zero coupon bond, i.e. an investment with portfolio insurance. The optimal portfolio is found when the investment...... opportunities consist of a risky reference fund, a risk-free asset and a structured bond. Key model elements are the trading strategy and utility function of the investor. Our numerical results indicate structured bonds do have basis for consideration in the optimal portfolio. The product holdings...

  13. Additional disulfide bonds in insulin

    DEFF Research Database (Denmark)

    Vinther, Tine N; Pettersson, Ingrid; Huus, Kasper

    2015-01-01

    The structure of insulin, a glucose homeostasis-controlling hormone, is highly conserved in all vertebrates and stabilized by three disulfide bonds. Recently, we designed a novel insulin analogue containing a fourth disulfide bond located between positions A10-B4. The N-terminus of insulin's B......-chain is flexible and can adapt multiple conformations. We examined how well disulfide bond predictions algorithms could identify disulfide bonds in this region of insulin. In order to identify stable insulin analogues with additional disulfide bonds, which could be expressed, the Cβ cut-off distance had...... in comparison to analogues with additional disulfide bonds that were more difficult to predict. In contrast, addition of the fourth disulfide bond rendered all analogues resistant to fibrillation under stress conditions and all stable analogues bound to the insulin receptor with picomolar affinities. Thus...

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

    Science.gov (United States)

    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 bond failures at the resin/enamel interface.

  15. Redshift or adduct stabilization -- a computational study of hydrogen bonding in adducts of protonated carboxylic acids

    DEFF Research Database (Denmark)

    Olesen, Solveig Gaarn; Hammerum, Steen

    2009-01-01

    changes and the redshift favor the Z OH group, matching the results of NBO and AIM calculations. This reflects that the thermochemistry of adduct formation is not a good measure of the hydrogen bond strength in charged adducts, and that the ionic interactions in the E and Z adducts of protonated......It is generally expected that the hydrogen bond strength in a D-H-A adduct is predicted by the difference between the proton affinities of D and A, measured by the adduct stabilization, and demonstrated by the IR redshift of the D-H bond stretching vibrational frequency. These criteria do...... not always yield consistent predictions, as illustrated by the hydrogen bonds formed by the E and Z OH groups of protonated carboxylic acids. The delta-PA and the stabilization of a series of hydrogen bonded adducts indicate that the E OH group forms the stronger hydrogen bonds, whereas the bond length...

  16. Persistence Length of Stable Microtubules

    Science.gov (United States)

    Hawkins, Taviare; Mirigian, Matthew; Yasar, M. Selcuk; Ross, Jennifer

    2011-03-01

    Microtubules are a vital component of the cytoskeleton. As the most rigid of the cytoskeleton filaments, they give shape and support to the cell. They are also essential for intracellular traffic by providing the roadways onto which organelles are transported, and they are required to reorganize during cellular division. To perform its function in the cell, the microtubule must be rigid yet dynamic. We are interested in how the mechanical properties of stable microtubules change over time. Some ``stable'' microtubules of the cell are recycled after days, such as in the axons of neurons or the cilia and flagella. We measured the persistence length of freely fluctuating taxol-stabilized microtubules over the span of a week and analyzed them via Fourier decomposition. As measured on a daily basis, the persistence length is independent of the contour length. Although measured over the span of the week, the accuracy of the measurement and the persistence length varies. We also studied how fluorescently-labeling the microtubule affects the persistence length and observed that a higher labeling ratio corresponded to greater flexibility. National Science Foundation Grant No: 0928540 to JLR.

  17. Vector-based model of elastic bonds for simulation of granular solids.

    Science.gov (United States)

    Kuzkin, Vitaly A; Asonov, Igor E

    2012-11-01

    A model (further referred to as the V model) for the simulation of granular solids, such as rocks, ceramics, concrete, nanocomposites, and agglomerates, composed of bonded particles (rigid bodies), is proposed. It is assumed that the bonds, usually representing some additional gluelike material connecting particles, cause both forces and torques acting on the particles. Vectors rigidly connected with the particles are used to describe the deformation of a single bond. The expression for potential energy of the bond and corresponding expressions for forces and torques are derived. Formulas connecting parameters of the model with longitudinal, shear, bending, and torsional stiffnesses of the bond are obtained. It is shown that the model makes it possible to describe any values of the bond stiffnesses exactly; that is, the model is applicable for the bonds with arbitrary length/thickness ratio. Two different calibration procedures depending on bond length/thickness ratio are proposed. It is shown that parameters of the model can be chosen so that under small deformations the bond is equivalent to either a Bernoulli-Euler beam or a Timoshenko beam or short cylinder connecting particles. Simple analytical expressions, relating parameters of the V model with geometrical and mechanical characteristics of the bond, are derived. Two simple examples of computer simulation of thin granular structures using the V model are given.

  18. ExperimentalStudy on Bonding Properties Between Steel Strand and Concrete at Cryogenic Temperatures

    Institute of Scientific and Technical Information of China (English)

    谢剑; 爱的歌; 雷光成; 聂治盟

    2016-01-01

    To study the bonding properties between steel strand and concrete at room and cryogenic temperatures, a series of center pullout experiments were conducted on 96 bonding anchorage specimens at the lowest tempera-ture of-165℃. The impacts on the bonding property of such parameters as the temperature, concrete strength, the relative concrete cover thickness, and the relative anchorage length were analyzed. The test results indicate that the changes in temperature have a clear effect on the bonding property between steel strand and concrete. As the tem-perature decreases, the bond stress, which corresponds to a 1 mm slip of steel strand in relation to concrete, and the ultimate bond strength initially increase and subsequently decrease at the inflection point of-80℃. The impact of the concrete strength on the bonding property, as shown by the tensile strength and the moisture content interaction, indicates that the bond stress vs concrete strength curve initially increases and later decreases with a decrease in temperature; the bond stress vs concrete cover thickness curve linearly increases, but the bond stress vs anchorage length curve linearly decreases at first and finally levels off.

  19. IMF Length Scales and Predictability: The Two Length Scale Medium

    Science.gov (United States)

    Collier, Michael R.; Szabo, Adam; Slavin, James A.; Lepping, R. P.; Kokubun, S.

    1999-01-01

    We present preliminary results from a systematic study using simultaneous data from three spacecraft, Wind, IMP 8 (Interplanetary Monitoring Platform) and Geotail to examine interplanetary length scales and their implications on predictability for magnetic field parcels in the typical solar wind. Time periods were selected when the plane formed by the three spacecraft included the GSE (Ground Support Equipment) x-direction so that if the parcel fronts were strictly planar, the two adjacent spacecraft pairs would determine the same phase front angles. After correcting for the motion of the Earth relative to the interplanetary medium and deviations in the solar wind flow from radial, we used differences in the measured front angle between the two spacecraft pairs to determine structure radius of curvature. Results indicate that the typical radius of curvature for these IMF parcels is of the order of 100 R (Sub E). This implies that there are two important IMF (Interplanetary Magnetic Field) scale lengths relevant to predictability: (1) the well-established scale length over which correlations observed by two spacecraft decay along a given IMF parcel, of the order of a few tens of Earth radii and (2) the scale length over which two spacecraft are unlikely to even observe the same parcel because of its curvature, of the order of a hundred Earth radii.

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

    Science.gov (United States)

    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.

  1. CEBAF Upgrade Bunch Length Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mahmoud [Old Dominion Univ., Norfolk, VA (United States)

    2016-05-01

    Many accelerators use short electron bunches and measuring the bunch length is important for efficient operations. CEBAF needs a suitable bunch length because bunches that are too long will result in beam interruption to the halls due to excessive energy spread and beam loss. In this work, bunch length is measured by invasive and non-invasive techniques at different beam energies. Two new measurement techniques have been commissioned; a harmonic cavity showed good results compared to expectations from simulation, and a real time interferometer is commissioned and first checkouts were performed. Three other techniques were used for measurements and comparison purposes without modifying the old procedures. Two of them can be used when the beam is not compressed longitudinally while the other one, the synchrotron light monitor, can be used with compressed or uncompressed beam.

  2. Keeping disease at arm's length

    DEFF Research Database (Denmark)

    Lassen, Aske Juul

    2015-01-01

    active ageing change everyday life with chronic disease, and how do older people combine an active life with a range of chronic diseases? The participants in the study use activities to keep their diseases at arm’s length, and this distancing of disease at the same time enables them to engage in social...... and physical activities at the activity centre. In this way, keeping disease at arm’s length is analysed as an ambiguous health strategy. The article shows the importance of looking into how active ageing is practised, as active ageing seems to work well in the everyday life of the older people by not giving...... emphasis to disease. The article is based on ethnographic fieldwork and uses vignettes of four participants to show how they each keep diseases at arm’s length....

  3. Spreading lengths of Hermite polynomials

    CERN Document Server

    Sánchez-Moreno, P; Manzano, D; Yáñez, R; 10.1016/j.cam.2009.09.043

    2009-01-01

    The Renyi, Shannon and Fisher spreading lengths of the classical or hypergeometric orthogonal polynomials, which are quantifiers of their distribution all over the orthogonality interval, are defined and investigated. These information-theoretic measures of the associated Rakhmanov probability density, which are direct measures of the polynomial spreading in the sense of having the same units as the variable, share interesting properties: invariance under translations and reflections, linear scaling and vanishing in the limit that the variable tends towards a given definite value. The expressions of the Renyi and Fisher lengths for the Hermite polynomials are computed in terms of the polynomial degree. The combinatorial multivariable Bell polynomials, which are shown to characterize the finite power of an arbitrary polynomial, play a relevant role for the computation of these information-theoretic lengths. Indeed these polynomials allow us to design an error-free computing approach for the entropic moments (w...

  4. Bond strength with custom base indirect bonding techniques.

    Science.gov (United States)

    Klocke, Arndt; Shi, Jianmin; Kahl-Nieke, Bärbel; Bismayer, Ulrich

    2003-04-01

    Different types of adhesives for indirect bonding techniques have been introduced recently. But there is limited information regarding bond strength with these new materials. In this in vitro investigation, stainless steel brackets were bonded to 100 permanent bovine incisors using the Thomas technique, the modified Thomas technique, and light-cured direct bonding for a control group. The following five groups of 20 teeth each were formed: (1) modified Thomas technique with thermally cured base composite (Therma Cure) and chemically cured sealant (Maximum Cure), (2) Thomas technique with thermally cured base composite (Therma Cure) and chemically cured sealant (Custom I Q), (3) Thomas technique with light-cured base composite (Transbond XT) and chemically cured sealant (Sondhi Rapid Set), (4) modified Thomas technique with chemically cured base adhesive (Phase II) and chemically cured sealant (Maximum Cure), and (5) control group directly bonded with light-cured adhesive (Transbond XT). Mean bond strengths in groups 3, 4, and 5 were 14.99 +/- 2.85, 15.41 +/- 3.21, and 13.88 +/- 2.33 MPa, respectively, and these groups were not significantly different from each other. Groups 1 (mean bond strength 7.28 +/- 4.88 MPa) and 2 (mean bond strength 7.07 +/- 4.11 MPa) showed significantly lower bond strengths than groups 3, 4, and 5 and a higher probability of bond failure. Both the original (group 2) and the modified (group 1) Thomas technique were able to achieve bond strengths comparable to the light-cured direct bonded control group.

  5. Continuous lengths of oxide superconductors

    Science.gov (United States)

    Kroeger, Donald M.; List, III, Frederick A.

    2000-01-01

    A layered oxide superconductor prepared by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon. A continuous length of a second substrate ribbon is overlaid on the first substrate ribbon. Sufficient pressure is applied to form a bound layered superconductor precursor powder between the first substrate ribbon and the second substrate ribbon. The layered superconductor precursor is then heat treated to establish the oxide superconducting phase. The layered oxide superconductor has a smooth interface between the substrate and the oxide superconductor.

  6. Overview of bunch length measurements.

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A. H.

    1999-02-19

    An overview of particle and photon beam bunch length measurements is presented in the context of free-electron laser (FEL) challenges. Particle-beam peak current is a critical factor in obtaining adequate FEL gain for both oscillators and self-amplified spontaneous emission (SASE) devices. Since measurement of charge is a standard measurement, the bunch length becomes the key issue for ultrashort bunches. Both time-domain and frequency-domain techniques are presented in the context of using electromagnetic radiation over eight orders of magnitude in wavelength. In addition, the measurement of microbunching in a micropulse is addressed.

  7. 27 CFR 28.66 - Strengthening bonds.

    Science.gov (United States)

    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...

  8. Elongated Silicon-Carbon Bonds at Graphene Edges.

    Science.gov (United States)

    Chen, Qu; Robertson, Alex W; He, Kuang; Gong, Chuncheng; Yoon, Euijoon; Kirkland, Angus I; Lee, Gun-Do; Warner, Jamie H

    2016-01-26

    We study the bond lengths of silicon (Si) atoms attached to both armchair and zigzag edges using aberration corrected transmission electron microscopy with monochromation of the electron beam. An in situ heating holder is used to perform imaging of samples at 800 °C in order to reduce chemical etching effects that cause rapid structure changes of graphene edges at room temperature under the electron beam. We provide detailed bond length measurements for Si atoms both attached to edges and also as near edge substitutional dopants. Edge reconstruction is also involved with the addition of Si dopants. Si atoms bonded to the edge of graphene are compared to substitutional dopants in the bulk lattice and reveal reduced out-of-plane distortion and bond elongation. An extended linear array of Si atoms at the edge is found to be energy-favorable due to inter-Si interactions. These results provide detailed structural information about the Si-C bonds in graphene, which may have importance in future catalytic and electronic applications.

  9. H-Bonded Liquid Crystalline Polymer Network Materials

    Institute of Scientific and Technical Information of China (English)

    LIN Hong-Cheu; HENDRIANTO Jemmy

    2001-01-01

    @@Side-chain copolymers, poly(mOBA-co-mStilb)s, composed of proton acceptors (stilbazoles) and proton donors (benzoic acids) connected to polyacrylate backbone with different methylene spacer lengths (m = 6 and 10) were prepared in different donor/acceptor molar ratios. The H-bonded copolymeric networks were formed once they were synthesized, and showed more homogenous phase than the physical-blended supramolecular networks consisting of donor and acceptor homopolymers, i.e.H-bonded blends of PmOBA and PmStilb. In order to compare the effects of the backbone connection of these H-bonded copolymers and blends, we also built monomer-monomer and polymer-monomer H-bonded complexes of similar structures (shown in Fig. 1). DSC, POM, and powder XRD studies reveal that the copolymers (m = 10)with mole fractions of benzoic acids between 0.33-0.83 show the smectic A (SMA) phase with layer spacing values between 42.22A-50.47A (increases with higher H-bonded crosslinking density between benzoic acids and stilbazoles), while for m = 6, liquid crystalline behavior still can be observed at 0.89 molar fraction of benzoic acids. However, on the basis of powder XRD study it is found that the d spacing values of H-bonded copolymers with m = 6 in the SmA phase increase with higher molar ratios of benzoic acids, which is agreed with the formation of microphase separation due to the hydrogen bonds of benzoic acids connected themselves from the same backbone. The isotropization temperatures of the H-bonded copolymers and blends increase as the molar ratios of benzoic acids increase, while the higher crosslinking density of the H-bonded copolymeric networks and blends can stabilize the liquid crystalline phase.

  10. H-Bonded Liquid Crystalline Polymer Network Materials

    Institute of Scientific and Technical Information of China (English)

    LIN; Hong-Cheu

    2001-01-01

    Side-chain copolymers, poly(mOBA-co-mStilb)s, composed of proton acceptors (stilbazoles) and proton donors (benzoic acids) connected to polyacrylate backbone with different methylene spacer lengths (m = 6 and 10) were prepared in different donor/acceptor molar ratios. The H-bonded copolymeric networks were formed once they were synthesized, and showed more homogenous phase than the physical-blended supramolecular networks consisting of donor and acceptor homopolymers, i.e.H-bonded blends of PmOBA and PmStilb. In order to compare the effects of the backbone connection of these H-bonded copolymers and blends, we also built monomer-monomer and polymer-monomer H-bonded complexes of similar structures (shown in Fig. 1). DSC, POM, and powder XRD studies reveal that the copolymers (m = 10)with mole fractions of benzoic acids between 0.33-0.83 show the smectic A (SMA) phase with layer spacing values between 42.22A-50.47A (increases with higher H-bonded crosslinking density between benzoic acids and stilbazoles), while for m = 6, liquid crystalline behavior still can be observed at 0.89 molar fraction of benzoic acids. However, on the basis of powder XRD study it is found that the d spacing values of H-bonded copolymers with m = 6 in the SmA phase increase with higher molar ratios of benzoic acids, which is agreed with the formation of microphase separation due to the hydrogen bonds of benzoic acids connected themselves from the same backbone. The isotropization temperatures of the H-bonded copolymers and blends increase as the molar ratios of benzoic acids increase, while the higher crosslinking density of the H-bonded copolymeric networks and blends can stabilize the liquid crystalline phase.……

  11. Length Normalization in XML Retrieval

    NARCIS (Netherlands)

    Kamps, Jaap; Rijke, Maarten de; Sigurbjörnsson, Börkur

    2005-01-01

    The full paper appeared as: J. Kamps, M. de Rijke, and B. Sigurbj¨ornsson, “Length Normalization in XML Retrieval,” In: Proceedings 27th Annual International ACM SIGIR Conference (SIGIR 2004), pages 80-87, 2004.

  12. Finite length Taylor Couette flow

    Science.gov (United States)

    Streett, C. L.; Hussaini, M. Y.

    1987-01-01

    Axisymmetric numerical solutions of the unsteady Navier-Stokes equations for flow between concentric rotating cylinders of finite length are obtained by a spectral collocation method. These representative results pertain to two-cell/one-cell exchange process, and are compared with recent experiments.

  13. 7 Length-weight relationship

    African Journals Online (AJOL)

    Administrator

    from which stomachs were extracted for the analysis of the food contents, using frequency of occurrence, numerical and ... both fish species showed strong correlation between the weight and length with correlation coefficient (r) and ..... Basic data on the assessment of Sphyraena ... review of methods and their application.

  14. Persistence length of dendronized polymers

    NARCIS (Netherlands)

    Mikhailov, I.V.; Darinskii, A.A.; Zhulina, E.B.; Borisov, O.V.; Leermakers, F.A.M.

    2015-01-01

    We present numerical results for the thermodynamic rigidity and induced persistence length of dendronized polymers with systematically varied topology of their grafts obtained by the Scheutjens-Fleer self-consistent field method. The results were compared to predictions of an analytical mean-fiel

  15. Fractional baud-length coding

    Directory of Open Access Journals (Sweden)

    J. Vierinen

    2011-06-01

    Full Text Available We present a novel approach for modulating radar transmissions in order to improve target range and Doppler estimation accuracy. This is achieved by using non-uniform baud lengths. With this method it is possible to increase sub-baud range-resolution of phase coded radar measurements while maintaining a narrow transmission bandwidth. We first derive target backscatter amplitude estimation error covariance matrix for arbitrary targets when estimating backscatter in amplitude domain. We define target optimality and discuss different search strategies that can be used to find well performing transmission envelopes. We give several simulated examples of the method showing that fractional baud-length coding results in smaller estimation errors than conventional uniform baud length transmission codes when estimating the target backscatter amplitude at sub-baud range resolution. We also demonstrate the method in practice by analyzing the range resolved power of a low-altitude meteor trail echo that was measured using a fractional baud-length experiment with the EISCAT UHF system.

  16. Cavity length below chute aerators

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    It is proved that air entrainment is one of the efficient measures dealing with cavi-tation control for the release works of hydropower projects. There are many factors to be considered in designing a chute aerator. One of the most important factors concerns the cavity length below the aerator,which has outstanding effects on air entrainment against cavitation damage. It is crucial to determine reasonable emergence angle for the calculation of the cavity length. In the present paper the overall effects of structural and hydraulic parameters on the emergence angle of the flow from the aerator were analyzed. Four improved expressions of the emer-gence angle with weight coefficient were investigated through experimental data of 68 points observed from 12 aerators of 6 hydropower projects,of both model and prototype,on the basis of error theory. A method to calculate the cavity length be-low aerators was suggested,which considers overall effects of the above men-tioned parameters. Comparison between the method in this paper and the other five methods of calculating the cavity length showed that the present method is much more reliable than the existing methods while the mean error of the method is less than others.

  17. Cavity length below chute aerators

    Institute of Scientific and Technical Information of China (English)

    WU JianHua; RUAN ShiPing

    2008-01-01

    It is proved that air entrainment is one of the efficient measures dealing with cavitation control for the release works of hydropower projects. There are many factors to be considered in designing a chute aerator. One of the most important factors concerns the cavity length below the aerator, which has outstanding effects on air entrainment against cavitation damage. It is crucial to determine reasonable emergence angle for the calculation of the cavity length. In the present paper the overall effects of structural and hydraulic parameters on the emergence angle of the flow from the aerator were analyzed. Four improved expressions of the emergence angle with weight coefficient were investigated through experimental data of 68 points observed from 12 aerators of 6 hydropower projects, of both model and prototype, on the basis of error theory. A method to calculate the cavity length below aerators was suggested, which considers overall effects of the above mentioned parameters. Comparison between the method in this paper and the other five methods of calculating the cavity length showed that the present method is much more reliable than the existing methods while the mean error of the method is less than others.

  18. Cyclic Codes of Length 2

    Indian Academy of Sciences (India)

    Manju Pruthi

    2001-11-01

    In this paper explicit expressions of + 1 idempotents in the ring $R = F_q[X]/\\langle X^{2^m}-1\\rangle$ are given. Cyclic codes of length 2 over the finite field , of odd characteristic, are defined in terms of their generator polynomials. The exact minimum distance and the dimension of the codes are obtained.

  19. Calculation of activation energies for hydrogen-atom abstractions by radicals containing carbon triple bonds

    Science.gov (United States)

    Brown, R. L.; Laufer, A. H.

    1981-01-01

    Activation energies are calculated by the bond-energy-bond-order (BEBO) and the bond-strength-bond-length (BSBL) methods for the reactions of C2H radicals with H2, CH4, and C2H6 and for the reactions of CN radicals with H2 and CH4. The BSBL technique accurately predicts the activation energies for these reactions while the BEBO method yields energies averaging 9 kcal higher than those observed. A possible reason for the disagreement is considered.

  20. Swendsen-Wang is faster than single-bond dynamics

    CERN Document Server

    Ullrich, Mario

    2012-01-01

    We prove that the spectral gap of the Swendsen-Wang dynamics for the random-cluster model is larger than the spectral gap of a single-bond dynamics, that updates only a single edge per step. For this we give a representation of the algorithms on the joint (Potts/random-cluster) model. Furthermore we obtain upper and lower bounds on the mixing time of the single-bond dynamics on the discrete d-dimensional torus of side length L at the Potts transition temperature for $q$ large enough that are exponential in L^{d-1}, complementing a result of Borgs, Chayes and Tetali.

  1. On some hydrogen bond correlations at high pressures

    Science.gov (United States)

    Sikka, S. K.

    2007-09-01

    In situ high pressure neutron diffraction measured lengths of O H and H O pairs in hydrogen bonds in substances are shown to follow the correlation between them established from 0.1 MPa data on different chemical compounds. In particular, the conclusion by Nelmes et al that their high pressure data on ice VIII differ from it is not supported. For compounds in which the O H stretching frequencies red shift under pressure, it is shown that wherever structural data is available, they follow the stretching frequency versus H O (or O O) distance correlation. For compounds displaying blue shifts with pressure an analogy appears to exist with improper hydrogen bonds.

  2. Solvent effects on hydrogen bonding between primary alcohols and esters

    Institute of Scientific and Technical Information of China (English)

    DHARMALINGAM K.; RAMACHANDRAN K.; SIVAGURUNATHAN P.

    2006-01-01

    The interaction by hydrogen bond formation of some primary alcohols (1-heptanol, 1-octanol and 1-decanol) with esters (methyl methacrylate, ethyl methacrylate and butyl methacrylate) was investigated in non-polar solvents viz., n-heptane,CCh and benzene by means of FTIR spectroscopy. Formation constants and free energy changes of complex formation were determined. The dependence of the equilibrium constants and free energy changes of complex formation on the alkyl chain length of both the alcohols and esters are discussed. The solvent effect on the hydrogen bond formation is discussed in terms of specific interaction between the solute and solvent.

  3. The effect of furcated hydrogen bond and coordination bond on luminescent behavior of metal-organic framework [CuCN·EIN]: a TDDFT study.

    Science.gov (United States)

    Wu, Danyang; Mi, Weihong; Ji, Min; Hao, Ce; Qiu, Jieshan

    2012-11-01

    The hydrogen bonding in electronically excited-state of the metal-organic framework [CuCN·EIN] was studied using time-dependent density functional theory (TDDFT). The representative fragment of [CuCN·EIN] was employed for the computation. The geometric structures, binding energies and IR spectra in both ground state and electronically excited state S(1) of the complex were computed using DFT and TDDFT methods to investigate excited-state hydrogen-bonding and coordination bonding, respectively. Based on the analysis of the frontier molecular orbitals and the electronic configuration of the complex, the ligand-to-metal charge transfer (LMCT) luminescence was confirmed. Furthermore, furcated hydrogen bonds are both strengthened in the S(1) state slightly. And then, the strengthening of the hydrogen bonds in the S(1) state goes against the charge transfer from ligand to metal and then should be in favor of the luminescence. In particular, we also discuss strengthening or weakening behavior of the coordination bonds in the S(1) state for the first time. Based on the results of the bond lengths and vibration frequency of the coordination bond, we can conclude that the coordination bond Cu(7)-N(8) is strengthened in the S(1) state. And the strengthening of the coordination bond Cu(7)-N(8) should also be in favor of the luminescence.

  4. A simplified indirect bonding technique

    Directory of Open Access Journals (Sweden)

    Radha Katiyar

    2014-01-01

    Full Text Available With the advent of lingual orthodontics, indirect bonding technique has become an integral part of practice. It involves placement of brackets initially on the models and then their transfer to teeth with the help of transfer trays. Problems encountered with current indirect bonding techniques used are (1 the possibility of adhesive flash remaining around the base of the brackets which requires removal (2 longer time required for the adhesive to gain enough bond strength for secure tray removal. The new simplified indirect bonding technique presented here overcomes both these problems.

  5. Photoinduced hydrogen-bonding dynamics.

    Science.gov (United States)

    Chu, Tian-Shu; Xu, Jinmei

    2016-09-01

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

  6. Wafer bonding applications and technology

    CERN Document Server

    Gösele, Ulrich

    2004-01-01

    During the past decade direct wafer bonding has developed into a mature materials integration technology. This book presents state-of-the-art reviews of the most important applications of wafer bonding written by experts from industry and academia. The topics include bonding-based fabrication methods of silicon-on-insulator, photonic crystals, VCSELs, SiGe-based FETs, MEMS together with hybrid integration and laser lift-off. The non-specialist will learn about the basics of wafer bonding and its various application areas, while the researcher in the field will find up-to-date information about this fast-moving area, including relevant patent information.

  7. Bond Growth under Temperature Gradient.

    Directory of Open Access Journals (Sweden)

    P.K. Satyawali

    1999-12-01

    Full Text Available Grain and bond growth for dry snow are determined by the distribution of temperature andtemperature gradient in the snow matrix. From the standpoint of particle approach and based oncubic packing structure, a bond growth model has been developed for TG metamorphism. The paper.highlights the importance of bond formation and its effect on snow viscosity and finally on the rateof settlement. This is very important for developing a numerical snow pack model if microstructureis considered to be a basic parameter. A few experiments have been carried out to validate bond formation under temperature gradient.

  8. Influence of charge and coordination number on bond dissociation energies, distances, and vibrational frequencies for the phosphorus-phosphorus bond.

    Science.gov (United States)

    Chitnis, Saurabh S; Whalen, J Marc; Burford, Neil

    2014-09-01

    We report a comprehensive and systematic experimental and computational assessment of the P-P bond in prototypical molecules that represent a rare series of known compounds. The data presented complement the existing solid-state structural data and previous computational studies to provide a thorough thermodynamic and electronic understanding of the P-P bond. Comparison of homolytic and heterolytic bond dissociation for tricoordinate-tricoordinate, tricoordinate-tetracoordinate, and tetracoordinate-tetracoordinate P-P bonds in frameworks 1-6 provides fundamental insights into covalent bonding. For all types of P-P bond discussed, homolytic dissociation is favored over heterolytic dissociation, although the distinction is small for 2(1+) and 6(1+). The presence of a single cationic charge in a molecule substantially strengthens the P-P bond (relative to analogous neutral frameworks) such that it is comparable with the C-C bond in alkanes. Nevertheless, P-P distances are remarkably independent of molecular charge or coordination number, and trends in values of d(PC) and νsymm(PC) imply that a molecular cationic charge is distributed over the alkyl substituents. In the gas phase, the diphosphonium dication 3(2+) has similar energy to two [PMe3](+) radical cations, so that it is the lattice enthalpy of 3[OTf]2 in the solid-state that enables isolation, highlighting that values from gas-phase calculations are poor guides for synthetic planning for ionic compounds. There are no relationships or correlations between bond lengths, strengths, and vibrational frequencies.

  9. Influence of chain topology and bond potential on the glass transition of polymer chains simulated with the bond fluctuation model

    Energy Technology Data Exchange (ETDEWEB)

    Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia (UNED), Senda del Rey 9, 28040 Madrid (Spain)], E-mail: jfreire@invi.uned.es

    2008-07-16

    The bond fluctuation model with a bond potential has been applied to investigation of the glass transition of linear chains and chains with a regular disposition of small branches. Cooling and subsequent heating curves are obtained for the chain energies and also for the mean acceptance probability of a bead jump. In order to mimic different trends to vitrification, a factor B gauging the strength of the bond potential with respect to the long-range potential (i.e. the intramolecular or intermolecular potential between indirectly bonded beads) has been introduced. (A higher value of B leads to a preference for the highest bond lengths and a higher total energy, implying a greater tendency to vitrify.) Different cases have been considered for linear chains: no long-range potential, no bond potential and several choices for B. Furthermore, two distinct values of B have been considered for alternate bonds in linear chains. In the case of the branched chains, mixed models with different values of B for bonds in the main chain and in the branches have also been investigated. The possible presence of ordering or crystallization has been characterized by calculating the collective light scattering function of the different samples after annealing at a convenient temperature below the onset of the abrupt change in the curves associated with a thermodynamic transition. It is concluded that ordering is inherited more efficiently in the systems with branched chains and also for higher values of B. The branched molecules with the highest B values in the main chain bonds exhibit two distinct transitions in the heating curves, which may be associated with two glass transitions. This behavior has been detected experimentally for chains with relatively long flexible branches.

  10. Reactive Bonding Film for Bonding Carbon Foam Through Metal Extrusion

    CERN Document Server

    Chertok, Maxwell; Irving, Michael; Neher, Christian; Tripathi, Mani; Wang, Ruby; Zheng, Gayle

    2016-01-01

    Future tracking detectors, such as those under development for the High Luminosity LHC, will require mechanical structures employing novel materials to reduce mass while providing excellent strength, thermal conductivity, and radiation tolerance. Adhesion methods for such materials are under study at present. This paper demonstrates the use of reactive bonding film as an adhesion method for bonding carbon foam.

  11. Digital Control of Bonding Force for Gold Wire Bonding Machine

    Directory of Open Access Journals (Sweden)

    Xiaochu Wang

    2013-01-01

    Full Text Available In order to digitally control the bonding force of a wire bonder precisely, this paper uses a DC solenoid as a force source, and by controlling the solenoid’s current, which causes the electromagnetic force, we can control the bonding force that capillary applies. The bonding force control system in this paper is composed of PC (Personal Computer and hypogyny MCU (Micro Controller Unit, which communicate using a RS485 interface. The digital value of a given bonding force is given by the PC to the MCU. By comparing the sampling current of the solenoid, and through PID regulation, D/A converter of the digital potentiometer and the solenoid driver circuit, the half-closed loop control system of bonding force is accomplished. Tuning of the PID parameters is accomplished with fuzzy adaptive control theory and simulated by Matlab simulink. The control system is tested by comparing the desired bonding force and the force actually applied and examming the relationship between bonding quality and bonding force.

  12. 29 CFR 2580.412-19 - Term of the bond, discovery period, other bond clauses.

    Science.gov (United States)

    2010-07-01

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

  13. Bonding resin thixotropy and viscosity influence on dentine bond strength.

    Science.gov (United States)

    Niem, Thomas; Schmidt, Alexander; Wöstmann, Bernd

    2016-08-01

    To investigate the influence of bonding resin thixotropy and viscosity on dentine tubule penetration, blister formation and consequently on dentine bond strength as a function of air-blowing pressure (air-bp) intensity. Two HEMA-free, acetone-based, one-bottle self-etch adhesives with similar composition except disparate silica filler contents and different bonding resin viscosities were investigated. The high-filler-containing adhesive (G-Bond) featured a lower viscous bonding resin with inherent thixotropic resin (TR) properties compared to the low-filler-containing adhesive (iBond) exhibiting a higher viscous bonding resin with non-thixotropic resin (NTR) properties. Shear bond strength tests for each adhesive with low (1.5bar; 0.15MPa; n=16) and high (3.0bar; 0.30MPa; n=16) air-bp application were performed after specimen storage in distilled water (24h; 37.0±1.0°C). Results were analysed using a Student's t-test to identify statistically significant differences (padhesive specimens were morphologically characterised by SEM. Statistically significant bond strength differences were obtained for the thixotropic resin adhesive (high-pressure: 24.6MPa, low-pressure: 9.6MPa). While high air-bp specimens provided SEM images revealing resin-plugged dentine tubules, resin tags and only marginally blister structures, low air-bp left copious droplets and open dentine tubules. In contrast, the non-thixotropic resin adhesive showed no significant bond strength differences (high-pressure: 9.3MPa, low-pressure: 7.6MPa). A pressure-dependent distinct influence of bonding resin thixotropy and viscosity on dentine bond strength has been demonstrated. Stronger adhesion with high air-bp application is explained by improved resin fluidity and facilitated resin penetration into dentine tubules. Filler particles used in adhesive systems may induce thixotropic effects in bonding resin layers, accounting for improved free-flowing resin properties. In combination with high air

  14. Making End-Bonded Contacts to Carbon Nanotubes

    Science.gov (United States)

    Tang, Jianshi; Cao, Qing; Tulevski, George; Han, Shu-Jen

    As a promising candidate for post-Si era, the implementation of carbon nanotube (CNT)-based CMOS technology requires both high-quality channel and electrical contacts that can be scaled down to sub-10 nm. In the efforts of making scalable contacts to CNT, we have recently demonstrated low-resistance end-bonded carbide contacts, formed by the reaction of Mo with CNT through high-temperature annealing (>800 oC). Such end-bonded contact scheme leads to a size-independent contact resistance of about 30 kilo-ohms, which overcomes the scaling limit of conventional side contacts. In this talk, we will present another strategy to make end-bonded contacts to CNTs through thermal annealing at much lower temperatures (400-600 oC). The contact metals are carefully chosen to have a high carbon solubility, so that the carbon atoms could dissolve into the contacts to inherently form end-bonded contacts. Experimental results, including Raman, SEM, and electrical measurements, with different annealing temperatures will be presented. The length-dependent contact resistance for this new end-bonded contact will be evaluated and compared with that of conventional side contact and also end-bonded carbide contact.

  15. Short hydrogen bonds in the catalytic mechanism of serine proteases

    Directory of Open Access Journals (Sweden)

    VLADIMIR LESKOVAC

    2008-04-01

    Full Text Available The survey of crystallographic data from the Protein Data Bank for 37 structures of trypsin and other serine proteases at a resolution of 0.78–1.28 Å revealed the presence of hydrogen bonds in the active site of the enzymes, which are formed between the catalytic histidine and aspartate residues and are on average 2.7 Å long. This is the typical bond length for normal hydrogen bonds. The geometric properties of the hydrogen bonds in the active site indicate that the H atom is not centered between the heteroatoms of the catalytic histidine and aspartate residues in the active site. Taken together, these findings exclude the possibility that short “low-barrier” hydrogen bonds are formed in the ground state structure of the active sites examined in this work. Some time ago, it was suggested by Cleland that the “low-barrier hydrogen bond” hypothesis is operative in the catalytic mechanism of serine proteases, and requires the presence of short hydrogen bonds around 2.4 Å long in the active site, with the H atom centered between the catalytic heteroatoms. The conclusions drawn from this work do not exclude the validity of the “low-barrier hydrogen bond” hypothesis at all, but they merely do not support it in this particular case, with this particular class of enzymes.

  16. Mapping the force-field of a hydrogen bonded assembly

    Science.gov (United States)

    Moriarty, Philip

    2014-03-01

    Hydrogen-bonding underpins the structure, properties, and dynamics of a vast array of systems spanning a wide variety of scientific fields. From the striking complexity of the phase diagram of H2O and the elegance of base pair interactions in DNA, to the directionality inherent in supramolecular self-assembly at surfaces, hydrogen bonds play an essential role in directing intermolecular forces. Yet fundamental aspects of the H-bond, including the magnitude of the force and binding energy, force constant, and decay length associated with the interaction, have been vigorously debated for many decades. I will discuss how dynamic force microscopy (DFM) using a qPlus sensor can quantitatively map the tip-sample force-field for naphthalene tetracarboxylic diimide (NTCDI) molecules hydrogen-bonded in 2D assemblies. A comparison of experimental images and force spectra with their simulated counterparts from density functional theory calculations shows that image contrast due to intermolecular hydrogen bonds arises fundamentally from charge density depletion due to strong tip-sample interactions. Interpretation of DFM images of hydrogen bonds therefore necessitates detailed consideration of the coupled tip-molecule system: analyses based on intermolecular charge density in the absence of the tip fail to capture the essential physical chemistry underpinning the imaging mechanism.

  17. Red- and blue-shifted hydrogen bonds in the cis-trans noncyclic formic acid dimer.

    Science.gov (United States)

    Zhou, Pan-Pan; Qiu, Wen-Yuan

    2009-08-01

    The cis-trans noncyclic formic acid dimer was studied by means of MP2 method with 6-31G(d,p), 6-31+G(d,p) and 6-311+G(d,p) basis sets. It exhibits simultaneously red-shifted O-H...O and blue-shifted C-H...O hydrogen bonds. AIM and NBO analyses are performed at the MP2/6-31+G(d,p) level to explore their properties and origins. AIM analysis provides the evidence that the O-H bond becomes weaker and the C-H bond becomes stronger upon the hydrogen bond formations. Intermolecular and intramolecular hyperconjugations have important influence on the electron densities in the X-H (X = O, C) sigma bonding orbital and its sigma* antibonding orbital. The electron densities in the two orbitals are closely connected with the X-H (X = O, C) bond length, and they are used to quantitatively estimate the bond length variation. The larger amount of charge transfer in the red-shifted O-H...O hydrogen bond is due to its favorable H...O electron channel, whereas the H...O electron channel in the blue-shifted C-H...O hydrogen bond is weaker. Structural reorganization effects shorten the C-H bond by approximately 30% when compared to the C-H bond contraction upon the dimerization. Strikingly, it leads to a small elongation and a slight red shift of the O-H bond. Both rehybridization and repolarization result in the X-H (X = O, C) bond contraction, but their effects on the O-H bond do not hold a dominant position. The hydrogen-bonding processes go through the electrostatic attractions, van der Waals interactions, charge-transfer interactions, hydrogen-bonding interactions and electrostatic repulsions. Electrostatic attractions are of great importance on the origin of the red-shifted O-H...O hydrogen bond, especially the strong H(delta+)...O(delta-) attraction. For the blue-shifted C-H...O hydrogen bond, the considerable nucleus-nucleus repulsion between H and O atoms caused by the strong electrostatic attraction between C and O atoms is a possible reason for the C-H bond contraction and

  18. Length of a Hanging Cable

    Directory of Open Access Journals (Sweden)

    Eric Costello

    2011-01-01

    Full Text Available The shape of a cable hanging under its own weight and uniform horizontal tension between two power poles is a catenary. The catenary is a curve which has an equation defined by a hyperbolic cosine function and a scaling factor. The scaling factor for power cables hanging under their own weight is equal to the horizontal tension on the cable divided by the weight of the cable. Both of these values are unknown for this problem. Newton's method was used to approximate the scaling factor and the arc length function to determine the length of the cable. A script was written using the Python programming language in order to quickly perform several iterations of Newton's method to get a good approximation for the scaling factor.

  19. INTERPOLATION WITH RESTRICTED ARC LENGTH

    Institute of Scientific and Technical Information of China (English)

    Petar Petrov

    2003-01-01

    For given data (ti,yi), I= 0,1,…,n,0 = t0 <t1 <…<tn = 1we study constrained interpolation problem of Favard type inf{‖f"‖∞|f∈W2∞[0,1],f(ti)=yi,i=0,…,n,l(f;[0,1])≤l0}, wherel(f";[0,1])=∫1 0 / 1+f'2(x)dx is the arc length off in [0,1]. We prove the existence of a solution f* of the above problem, that is a quadratic spline with a second derivative f"* , which coincides with one of the constants - ‖f"*‖∞,0,‖f"*‖∞ between every two consecutive knots. Thus, we extend a result ofKarlin concerning Favard problem, to the case of restricted length interpolation.

  20. Photoelastic Measurement of Strain Induced by Die-Bonding of GaAs Chip on a Copper Heatsink Plate

    Science.gov (United States)

    Chu, Tao; Yamada, Masayoshi

    1999-02-01

    Die-bonding-induced strain in a GaAs chip bonded on a copper heatsink plate has been measured with a reflection type of infrared polariscope.The spatial distributions of bonding-induced strain were seen to vary from sample to sample.The maximum value of the bonding-induced strain was found to be of the order of 10-4, which corresponded to about 1/10 of that estimated from the thermal expansion difference for the unit length between GaAs and copper when it was cooled down from the die-bonding temperature to the room temperature.

  1. Minimal Length, Measurability and Gravity

    Directory of Open Access Journals (Sweden)

    Alexander Shalyt-Margolin

    2016-03-01

    Full Text Available The present work is a continuation of the previous papers written by the author on the subject. In terms of the measurability (or measurable quantities notion introduced in a minimal length theory, first the consideration is given to a quantum theory in the momentum representation. The same terms are used to consider the Markov gravity model that here illustrates the general approach to studies of gravity in terms of measurable quantities.

  2. Molecularly Tuning the Radicaloid N-H···O═C Hydrogen Bond.

    Science.gov (United States)

    Lu, Norman; Chung, Wei-Cheng; Ley, Rebecca M; Lin, Kwan-Yu; Francisco, Joseph S; Negishi, Ei-Ichi

    2016-03-01

    Substituent effects on the open shell N-H···O═C hydrogen-bond has never been reported. This study examines how 12 functional groups composed of electron donating groups (EDG), halogen atoms and electron withdrawing groups (EWG) affect the N-H···O═C hydrogen-bond properties in a six-membered cyclic model system of O═C(Y)-CH═C(X)N-H. It is found that group effects on this open shell H-bonding system are significant and have predictive trends when X = H and Y is varied. When Y is an EDG, the N-H···O═C hydrogen-bond is strengthened; and when Y is an EWG, the bond is weakened; whereas the variation in electronic properties of X group do not exhibit a significant impact upon the hydrogen bond strength. The structural impact of the stronger N-H···O═C hydrogen-bond are (1) shorter H and O distance, r(H···O) and (2) a longer N-H bond length, r(NH). The stronger N-H···O═C hydrogen-bond also acts to pull the H and O in toward one another which has an effect on the bond angles. Our findings show that there is a linear relationship between hydrogen-bond angle and N-H···O═C hydrogen-bond energy in this unusual H-bonding system. In addition, there is a linear correlation of the r(H···O) and the hydrogen bond energy. A short r(H···O) distance corresponds to a large hydrogen bond energy when Y is varied. The observed trends and findings have been validated using three different methods (UB3LYP, M06-2X, and UMP2) with two different basis sets.

  3. Ab initio structures for 90 degrees -twisted s-trans-1,3-butadiene and cyclooctatetraene: the naked sp2-sp2 bond.

    Science.gov (United States)

    Feller, David; Craig, Norman C; Matlin, Albert R

    2008-03-20

    The bond length of a carbon-carbon sp2-sp2 sigma-bond without the perturbing effects of pi-interactions has been estimated by high level calculations on two prototypical systems: a 90 degrees -twisted form of butadiene and the tub conformer of cyclooctatetraene. The former system yields a value of 1.4818 A, considerably longer than previous estimates. The corresponding bond length in the latter is slightly shorter due to some pi-electron delocalization.

  4. Experimental Assessment on the Flexural Bonding Performance of Concrete Beam with GFRP Reinforcing Bar under Repeated Loading

    Directory of Open Access Journals (Sweden)

    Minkwan Ju

    2015-01-01

    Full Text Available This study intends to investigate the flexural bond performance of glass fiber-reinforced polymer (GFRP reinforcing bar under repeated loading. The flexural bond tests reinforced with GFRP reinforcing bars were carried out according to the BS EN 12269-1 (2000 specification. The bond test consisted of three loading schemes: static, monotonic, and variable-amplitude loading to simulate ambient loading conditions. The empirical bond length based on the static test was 225 mm, whereas it was 317 mm according to ACI 440 1R-03. Each bond stress on the rib is released and bonding force is enhanced as the bond length is increased. Appropriate level of bond length may be recommended with this energy-based analysis. For the monotonic loading test, the bond strengths at pullout failure after 2,000,000 cycles were 10.4 MPa and 6.5 MPa, respectively: 63–70% of the values from the static loading test. The variable loading test indicated that the linear cumulative damage theory on GFRP bonding may not be appropriate for estimating the fatigue limit when subjected to variable-amplitude loading.

  5. Computational Chemistry of Adhesive Bonds

    Science.gov (United States)

    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.

  6. SOCIAL BONDING: REGULATION BY NEUROPEPTIDES

    Directory of Open Access Journals (Sweden)

    Claudia eLieberwirth

    2014-06-01

    Full Text Available 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.

  7. Quantum Confinement in Hydrogen Bond

    CERN Document Server

    Santos, Carlos da Silva dos; Ricotta, Regina Maria

    2015-01-01

    In this work, the quantum confinement effect is proposed as the cause of the displacement of the vibrational spectrum of molecular groups that involve hydrogen bonds. In this approach the hydrogen bond imposes a space barrier to hydrogen and constrains its oscillatory motion. We studied the vibrational transitions through the Morse potential, for the NH and OH molecular groups inside macromolecules in situation of confinement (when hydrogen bonding is formed) and non-confinement (when there is no hydrogen bonding). The energies were obtained through the variational method with the trial wave functions obtained from Supersymmetric Quantum Mechanics (SQM) formalism. The results indicate that it is possible to distinguish the emission peaks related to the existence of the hydrogen bonds. These analytical results were satisfactorily compared with experimental results obtained from infrared spectroscopy.

  8. Hydrogen bonding in the protic ionic liquid triethylammonium nitrate explored by density functional tight binding simulations

    Science.gov (United States)

    Zentel, Tobias; Kühn, Oliver

    2016-12-01

    The applicability of the density functional based tight binding (DFTB) method to the description of hydrogen bond dynamics and infrared (IR) spectroscopy is addressed for the exemplary protic ionic liquid triethylammonium nitrate. Potential energy curves for proton transfer in gas and liquid phases are shown to be comparable to the high level coupled cluster theory in the thermally accessible range of bond lengths. Geometric correlations in the hydrogen bond dynamics are analyzed for a cluster of six ion pairs. Comparing DFTB and DFT data lends further support for the reliability of the DFTB method. Therefore, DFTB bulk simulations are performed to quantify the extent of geometric correlations in terms of Pauling's bond order model. Further, IR absorption spectra are obtained using DFTB and analyzed putting emphasis on the signatures of hydrogen bonding in the NH-stretching and far IR hydrogen bond range.

  9. Hydrogen bonding in the protic ionic liquid triethylammonium nitrate explored by density functional tight binding simulations

    CERN Document Server

    Zentel, Tobias

    2016-01-01

    The applicability of the density functional based tight binding (DFTB) method to the description of hydrogen bond dynamics and infrared spectroscopy is addressed for the exemplary protic ionic liquid triethylammonium nitrate. Potential energy curves for proton transfer in gas and liquid phase are shown to be comparable to high level coupled cluster theory in the thermally accessible range of bond lengths. Geometric correlations in the hydrogen bond dynamics are analyzed for a cluster of six ion pairs. Comparing DFTB and regular DFT data lends further support for the reliability of the DFTB method. Therefore, DFTB bulk simulations are performed to quantify the extent of geometric correlations in terms of Pauling's bond order model. Further, infrared (IR) absorption spectra are obtained and analyzed putting emphasis on the signatures of hydrogen bonding in the NH-stretching and far IR hydrogen bond range.

  10. Dentin-bonding agents

    Directory of Open Access Journals (Sweden)

    João Carlos Gomes

    2008-01-01

    Full Text Available New dental restorative materials have been developed to meet not only the functional demands, but esthetics as well, and in the last few years an enormous range of new materials has appeared for use in dentistry. Among them, several adhesive systems, and different operative techniques for each group materials. Therefore, is indispensable for the professional to know about the properties, characteristics, and association of these materials with the dental structures, in order to select and use them correctly. Should conventional self-etching adhesive systems be used? This question encouraged this literature review to be conducted, with the aim of comparing the conventional adhesive systems with the self-etching systems and to look for scientific data that would help professionals to choose which adhesive system to use. When compared to conventional systems, it was noted that the self-etching systems show less sensitivity to technique, especially as regards errors the operator could commit. The self-etching systems, particularly the 2-step type, have shown equivalent values of bond strength, marginal microleakage and performance, therefore, will be an option for direct composite resin restorations in posterior teeth.

  11. Bonded Paths and van der Waals Interactions in Orpiment, As2S3

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, Gerald V.; Wallace, Adam F.; Zallen, Richard; Downs, R. T.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.

    2010-06-17

    Bond critical properties and bond paths have been calculated for the thioarsenide molecular crystal orpiment, As2S3. In addition to the intramolecular As-S bond paths and van der Waals As-S and S-S bond paths within the layers, intermolecular S-S, As-S and As-As van der Waals paths exist between the layers. The S-S bond paths between the layers are identified with the main interlayer restoring forces responsible for the vibrational internal-mode splitting and the low frequency rigid layer modes previously documented in infrared and Raman studies of orpiment. These S-S bond paths are comparable with those calculated for orthorhombic native sulfur and the As4Sn (n = 3,4,5) molecules for several arsenide molecular crystals. The As-S bond paths show that the two nonequivalent arsenic atoms are each coordinated by a highly distorted octahedral array of sulfur atoms. The octahedra consist of three As-S intramolecular bonded interactions and three longer van der Waals interactions (two intramolecular and one intermolecular). One of the arsenic atoms is also coordinated by an arsenic atom in an interlayer As-As bonded interaction. Laplacian isosurface envelopes calculated for the arsenic and sulfur atoms are comparable with those calculated for native arsenic and orthorhombic sulfur. The intermolecular As-S bond paths connect Lewis acid domains on arsenic and an Lewis base domains on sulfur. Van der Waals interactions are traditionally defined as attractive interactions other than those ascribed to bond formation. However, theoretical evidence and arguments, as well as the connection between the bond paths and the vibrational spectra, indicate that the van der Waals interactions in orpiment are directed bonded interactions in the Slater sense. The experimental bond lengths for the As-S and S-S bonded interactions decrease nonlinearly with the increasing value of the electron density at the bond critical point, concomitant with a decrease in the bonded radii of arsenic and

  12. Fragility and cooperativity concepts in hydrogen-bonded organic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Delpouve, N., E-mail: delpouve.nicolas@gmail.com [AMME-LECAP EA 4528 International Laboratory, University of Rouen, Avenue de l' Universite BP 12, 76801 Saint Etienne du Rouvray (France); Vuillequez, A.; Saiter, A.; Youssef, B.; Saiter, J.M. [AMME-LECAP EA 4528 International Laboratory, University of Rouen, Avenue de l' Universite BP 12, 76801 Saint Etienne du Rouvray (France)

    2012-09-01

    Molecular dynamics at the glass transition of three lactose/oil glassy systems have been investigated according to the cooperativity and fragility approaches. From Donth's approach, the cooperativity length is estimated by modulated temperature calorimetric measurements. Results reveal that modification of the disaccharide by oil leads to increase the disorder degree in the lactose, the size of the cooperative domains and the fragility index. These particular hydrogen-bonded organic glasses follow the general tendency observed on organic and inorganic polymers: the higher the cooperativity length, the higher the value of the fragility index at T{sub g}.

  13. Infrared Spectroscopic Investigation on CH Bond Acidity in Cationic Alkanes

    Science.gov (United States)

    Matsuda, Yoshiyuki; Xie, Min; Fujii, Asuka

    2016-06-01

    We have demonstrated large enhancements of CH bond acidities in alcohol, ether, and amine cations through infrared predissociation spectroscopy based on the vacuum ultraviolet photoionization detection. In this study, we investigate for the cationic alkanes (pentane, hexane, and heptane) with different alkyl chain lengths. The σ electrons are ejected in the ionization of alkanes, while nonbonding electrons are ejected in ionization of alcohols, ethers, and amines. Nevertheless, the acidity enhancements of CH in these cationic alkanes have also been demonstrated by infrared spectroscopy. The correlations of their CH bond acidities with the alkyl chain lengths as well as the mechanisms of their acidity enhancements will be discussed by comparison of infrared spectra and theoretical calculations.

  14. 27 CFR 24.153 - Strengthening bonds.

    Science.gov (United States)

    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...

  15. 27 CFR 19.246 - Strengthening bonds.

    Science.gov (United States)

    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...

  16. Continuum in the X-Z---Y weak bonds: Z= main group elements.

    Science.gov (United States)

    Joy, Jyothish; Jose, Anex; Jemmis, Eluvathingal D

    2016-01-15

    The Continuum in the variation of the X-Z bond length change from blue-shifting to red-shifting through zero- shifting in the X-Z---Y complex is inevitable. This has been analyzed by ab-initio molecular orbital calculations using Z= Hydrogen, Halogens, Chalcogens, and Pnicogens as prototypical examples. Our analysis revealed that, the competition between negative hyperconjugation within the donor (X-Z) molecule and Charge Transfer (CT) from the acceptor (Y) molecule is the primary reason for the X-Z bond length change. Here, we report that, the proper tuning of X- and Y-group for a particular Z- can change the blue-shifting nature of X-Z bond to zero-shifting and further to red-shifting. This observation led to the proposal of a continuum in the variation of the X-Z bond length during the formation of X-Z---Y complex. The varying number of orbitals and electrons available around the Z-atom differentiates various classes of weak interactions and leads to interactions dramatically different from the H-Bond. Our explanations based on the model of anti-bonding orbitals can be transferred from one class of weak interactions to another. We further take the idea of continuum to the nature of chemical bonding in general.

  17. A Study of Bond of Structural Timber and Carbon Fiber Reinforced Polymer Plate

    Directory of Open Access Journals (Sweden)

    Yongtaeg LEE

    2015-11-01

    Full Text Available The increase of well-being culture of problem related to environmental depletion of resource is not the growing interest in timber the natural material of construction markets. Also, the perception for historic preservation has been increased in respond to heightened interest. However, it is fairly difficult for architectural properties to maintain their durability because it was made by timber construction. Preventing traditional structure from damage and structural performance reduction is paramount in maintenance problem. A number of studies of reinforced method have been conducted in order to solve such a problem. In this paper, external bonded reinforcement and near-surface mounted was used as a way to reinforce timber structure’s durability. Bond strength for specimens with different bond length was investigated. As a result showed, maximum bond strength in bond length 300 mm from all method, was found to be not increased of bond strength over the certain bond length.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9702

  18. Platinum complexes having redox-active PPh2C[triple bond]CFc and/or C[triple bond]CFc as terminal or bridging ligands.

    Science.gov (United States)

    Díez, Alvaro; Lalinde, Elena; Teresa Moreno, M; Sánchez, Sergio

    2009-05-14

    A series of heteronuclear-Pt(ii) complexes containing ferrocenylethynyl units linked directly (Pt-C[triple bond]CFc) or through a phosphorous atom (Pt-PPh(2)C[triple bond]CFc) to the platinum center is reported. The reaction of derivative [cis-Pt(R(F))(2)(PPh(2)C[triple bond]CFc)(2)] (R(F) = C(6)F(5)) with the solvate complex [cis-Pt(R(F))(2)(thf)(2)] leads to the formation of an asymmetrical heteronuclear diplatinum complex [{Pt(R(F))(2)(mu-1kappaP:2eta(2)-PPh(2)C[triple bond]CFc)(2)}Pt(R(F))(2)] having the "cis-Pt(R(F))(2)" fragment coordinated to the triple bonds of both ferrocenylethynylphosphine units, while treatment of [cis-Pt(C[triple bond]CFc)(2)(PPh(2)C[triple bond]CR)(2)] (R = Fc , Ph , tBu ) with the same solvate [cis-Pt(R(F))(2)(thf)(2)], affords double ferrocenylacetylide-bridged diplatinum systems [{Pt(PPh(2)C[triple bond]CR)(2)(mu-eta(1):eta(2)-C[triple bond]CFc)(2)}Pt(R(F))(2)] . The solid-state structures of [cis/trans-Pt(R(F))(2)(PPh(2)C[triple bond]CFc)(2)] /, [cis-Pt(R(F))(2)(PPh(2)C[triple bond]CFc)(tht)] (tht = tetrahydrothiophene), [{Pt(R(F))(2)(mu-1kappaP:2eta(2)-PPh(2)C[triple bond]CFc)(2)}Pt(R(F))(2)] and [{Pt(PPh(2)C[triple bond]CtBu)(2)(mu-eta(1):eta(2)-C[triple bond]CFc)(2)}Pt(R(F))(2)] have been determined by X-ray diffraction methods. The electronic spectra and the electrochemical behaviour of all monoplatinum derivatives are discussed, showing a different extent of interaction between the remote ferrocenyl groups when they belong to PPh(2)C[triple bond]CFc or C[triple bond]CFc ligands. For the diplatinum systems and , containing bridging (kappaP:eta(2)-PPh(2)C[triple bond]CFc ) or (eta(1):eta(2)-C[triple bond, length as m-dash]CFc ) ligands, their electrochemical properties were also compared with the parent precursors.

  19. Pharmacologically induced erect penile length and stretched penile length are both good predictors of post-inflatable prosthesis penile length.

    Science.gov (United States)

    Osterberg, E C; Maganty, A; Ramasamy, R; Eid, J F

    2014-01-01

    Inflatable penile prosthesis (IPP) remains the gold standard for the surgical treatment of refractory erectile dysfunction; however, current literature to aid surgeons on how best to counsel patients on their postoperative inflated penile length is lacking. The aim of this study was to identify preoperative parameters that could better predict postoperative penile length following insertion of an IPP. Twenty men were enrolled in a prospective study examining penile lengths before and after IPP surgery. Patients with Peyronie's disease were excluded from this analysis. Baseline preoperative characteristics, including body mass index, history of hypertension, diabetes, Sexual Health Inventory for Men scores and/or prior radical prostatectomy were recorded. All patients underwent implantation with a three-piece inflatable Coloplast penile prosthesis. We compared stretched penile length to pharmacologically induced erect lengths. Postoperatively, we measured inflated penile lengths at 6 weeks and assessed patients' perception of penile size at 12 weeks. The median (±interquartile range) stretched penile length and pharmacologically induced erect penile length was 15 (±3) and 14.25 (±2) cm, respectively (P=0.5). Median post-prosthesis penile length (13.5±2.13 cm) was smaller than preoperative pharmacologically induced length (P=0.02) and preoperative stretched penile length (P=0.01). The majority of patients (70%) had a decrease in penile length (median loss 0.5±1.5 cm); however, this loss was perceptible by 43% of men. Stretched penile length and pharmacologically induced erect penile length were equally good predictors of postoperative inflated length (Spearman's correlation 0.8 and 0.9, respectively). Pharmacologically induced erect penile length and stretched penile lengths are equal predictors of post-prosthesis penile length. The majority of men will experience some decrease in penile length following prosthesis implantation; however <50% report a

  20. Conductance of Conjugated Molecular Wires: Length Dependence, Anchoring Groups, and Band Alignment

    DEFF Research Database (Denmark)

    Peng, Guowen; Strange, Mikkel; Thygesen, Kristian Sommer

    2009-01-01

    The conductance of π-conjugated molecular wires bonded to gold electrodes at zero bias is studied using density functional theory combined with nonequilibrium Green’s function method. For all systems considered, we find that the conductance length dependence follows the simple exponential law...

  1. Validating a Mentoring Relationship Quality Scale: Does Match Strength Predict Match Length?

    Science.gov (United States)

    Rhodes, Jean E.; Schwartz, Sarah E. O.; Willis, Margaret M.; Wu, Max B.

    2017-01-01

    Youth mentoring relationships have significant potential for promoting positive youth development. Nonetheless, the benefits derived from such relationships depend considerably on the length and quality of the bonds that are created between mentors and youth. Although some attention has been paid to youth's experience of relationship quality, few…

  2. Testing of Cotton Fiber Length

    Institute of Scientific and Technical Information of China (English)

    刘若华; 李汝勤

    2001-01-01

    To understand the influences of actual sampling conditions on cotton fiber length testing, this article presents a theoretic study on the distributions and fibrogram of the sample taken out by sampler from ideal sliver at a certain angle. From the distributions expression it can be found that the size of the sampler and the sampling angle are important factors which affect sampling, but if the sampling width is narrow enough, the influence of the sampling angle on the distributions and fibrogram is small enough to be omitted. This is an important conclusion for sampling, in light of this, some suggestions for designing new type sampler are put forward.

  3. Spherical silicon micromirrors bent by anodic bonding.

    Science.gov (United States)

    Wu, Tong; Yamasaki, Takahiro; Hokari, Ryohei; Hane, Kazuhiro

    2011-06-06

    We propose here a novel and stable method for fabricating spherical micromirror by bonding a flat freestanding single-crystal-silicon (SCS) membrane with a fulcrum on a glass substrate. Smooth convex spherical surface is achieved inside the fulcrum by the bending moment generated in the circumference of the SCS membrane. The surface profiles fit well with parabolic curves within 36nm RMS error indicating a good optical performance. By modifying the diameter of the fulcrum, we also demonstrate that it is possible to fabricate micromirrors with a wide range of focal length (0.4mm-1.6mm). The fabricated micromirrors are also used as the mold for replication of micro polymeric lenses. The surface profiles of the micromirrors are transferred to the polymeric replica with a high accuracy.

  4. Occurrence of protein disulfide bonds in different domains of life: a comparison of proteins from the Protein Data Bank.

    Science.gov (United States)

    Bošnjak, I; Bojović, V; Šegvić-Bubić, T; Bielen, A

    2014-03-01

    Disulfide bonds (SS bonds) are important post-translational modifications of proteins. They stabilize a three-dimensional (3D) structure (structural SS bonds) and also have the catalytic or regulatory functions (redox-active SS bonds). Although SS bonds are present in all groups of organisms, no comparative analyses of their frequency in proteins from different domains of life have been made to date. Using the Protein Data Bank, the number and subcellular locations of SS bonds in Archaea, Bacteria and Eukarya have been compared. Approximately three times higher frequency of proteins with SS bonds in eukaryotic secretory organelles (e.g. endoplasmic reticulum) than in bacterial periplasmic/secretory pathways was calculated. Protein length also affects the SS bond frequency: the average number of SS bonds is positively correlated with the length for longer proteins (>200 amino acids), while for the shorter and less stable proteins (proteins (250-350 amino acids) indicated a high number of SS bonds only in Archaea which could be explained by the need for additional protein stabilization in hyperthermophiles. The results emphasize higher capacity for the SS bond formation and isomerization in Eukarya when compared with Archaea and Bacteria.

  5. Physical Nature of Hydrogen Bond

    CERN Document Server

    Zhyganiuk, I V

    2015-01-01

    The physical nature and the correct definition of hydrogen bond (H-bond) are considered.\\,\\,The influence of H-bonds on the thermodynamic, kinetic, and spectroscopic properties of water is analyzed.\\,\\,The conventional model of H-bonds as sharply directed and saturated bridges between water molecules is incompatible with the behavior of the specific volume, evaporation heat, and self-diffusion and kinematic shear viscosity coefficients of water. On the other hand, it is shown that the variation of the dipole moment of a water molecule and the frequency shift of valence vibrations of a hydroxyl group can be totally explained in the framework of the electrostatic model of H-bond.\\,\\,At the same time, the temperature dependences of the heat capacity of water in the liquid and vapor states clearly testify to the existence of weak H-bonds.\\,\\,The analysis of a water dimer shows that the contribution of weak H-bonds to its ground state energy is approximately 4--5 times lower in comparison with the energy of electr...

  6. Bonding over Dentin Replacement Materials.

    Science.gov (United States)

    Meraji, Naghmeh; Camilleri, Josette

    2017-08-01

    Dentin replacement materials are necessary in large cavities to protect the pulp and reduce the bulk of filling material. These materials are layered with a composite resin restorative material. Microleakage caused by poor bonding of composite resin to underlying dentin replacement material will result in pulp damage. The aim of this study was to characterize the interface between dentin replacement materials and composite resin and to measure the shear bond strength after dynamic aging. Biodentine (Septodont, Saint Maur-des-Fosses, France), Theracal LC (Bisco, Schaumburg, IL), and Fuji IX (GC, Tokyo, Japan) were used as dentin replacement materials. They were then overlaid with a total-etch and bonding agent or a self-etch primer and composite resin or a glass ionomer cement. All combinations were thermocycled for 3000 cycles. The interface was characterized using scanning electron microscopy and elemental mapping. Furthermore, the shear bond strength was assessed. The Biodentine surface was modified by etching. The Theracal LC and Fuji IX microstructure was unchanged upon the application of acid etch. The Biodentine and glass ionomer interface showed an evident wide open space, and glass particles from the glass ionomer adhered to the Biodentine surface. Elemental migration was shown with aluminum, barium, fluorine, and ytterbium present in Biodentine from the overlying composite resin. Calcium was more stable. The bond strength between Theracal LC and composite using a total-etch technique followed by self-etch primer achieved the best bond strength values. Biodentine exhibited the weakest bond with complete failure of bonding shown after demolding and thermocycling. Dynamic aging is necessary to have clinically valid data. Bonding composite resin to water-based dentin replacement materials is still challenging, and further alternatives for restoration of teeth using such materials need to be developed. Copyright © 2017 American Association of Endodontists

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

    Science.gov (United States)

    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.

  8. The geometry of electronically-excited states: Vibronic intensity distributions and bond length changes

    Science.gov (United States)

    Wood, Dorothy Marie

    2001-12-01

    An exact power series expression has been obtained for the Franck-Condon integral (FCI) in the harmonic approximation. This expression is a function of a parameter Δ where Δ --> 0 as the frequencies of vibration in the two combining electronic states approach equality. These two characteristics, that of a power series in Δ and the fact that Δ --> 0 in certain situations, permit truncation of various functions involving FCI's. Such truncation was performed for the ratio S2v'0'' /S2(v'-1) 0'' , where the S2v'v'' are the FCI's, and the subscripts, in the usual notation, denote the vibrational quantum numbers in the two different electronic states. As a result, two approximations to the S2v'0'' /S2(v'-1) 0'' ratio were obtained: a linear approximation in Δ and a quadratic expression in Δ2. Maps of the Franck-Condon integrals, FCIM's, were found to be very useful. An FCIM is a plot of S2v'0'' (DRe) versus ΔRe for various values of the parameter v'. These FCIM's facilitated a test of the linear and quadratic approximations and led to a precise specification of the ranges of a within which they are valid. They resulted in the concept of a ``Franck-Condon window''. A Franck-Condon window (FCW) is that specific region of the FCIM (i.e., the range of ΔRe) in which the gross (i.e., non-numerical, vibronic intensity) pattern of some vibronic spectrum is represented. The vibrational intensity distributions in 60 different electronic transitions were subjected to Franck-Condon analysis using (i)the linear approximation, (ii)the quadratic approximation, (iii)the FCW approach, and (iv)the best fit to the FCIM. It was found that method (ii), (iii) & (iv) provided excellent agreement with experiment whereas method (i) produced mixed results. The analysis had some incidental benefits: it caused a reassignment of one vibronic spectrum and permitted a choice between two proposed alternative assignments for another vibronic spectrum.

  9. Large First Hyperpolarizabilities in Push-Pull Polyenes by Tuning Bond Length Alternation and Aromaticity

    Science.gov (United States)

    Marder, S. R.; Tiemann, B. G.; Friedli, A. C.; Cheng, L. -T.; Blanchard-Desce, M.

    1993-01-01

    Conjugated organic compounds with 3-phenyl-5-isoxazolone, or N, N'-diethylthiobarbituric acid acceptors have large first molecular hyperpolarizabilities in comparison to compounds with 4-nitrophenyl acceptors as measured by electric feld induced second harmonic generation, (EFISH), in chloroform, with 1.907 micron fundamental radiation.

  10. Analyses of cobalt-ligand and potassium-ligand bond lengths in metalloproteins: trends and patterns.

    Science.gov (United States)

    Brás, Natércia F; Ribeiro, António J M; Oliveira, Marina; Paixão, Nathália M; Tamames, Juan A; Fernandes, Pedro A; Ramos, Maria J

    2014-06-01

    Cobalt and potassium are biologically important metal elements that are present in a large array of proteins. Cobalt is mostly found in vivo associated with a corrin ring, which represents the core of the vitamin B12 molecule. Potassium is the most abundant metal in the cytosol, and it plays a crucial role in maintaining membrane potential as well as correct protein function. Here, we report a thorough analysis of the geometric properties of cobalt and potassium coordination spheres that was performed with high resolution on a representative set of structures from the Protein Data Bank and complemented by quantum mechanical calculations realized at the DFT level of theory (B3LYP/ SDD) on mononuclear model systems. The results allowed us to draw interesting conclusions on the structural characteristics of both Co and K centers, and to evaluate the importance of effects such as their association energies and intrinsic thermodynamic stabilities. Overall, the results obtained provide useful data for enhancing the atomic models normally applied in theoretical and computational studies of Co or K proteins performed at the quantum mechanical level, and for developing molecular mechanical parameters for treating Co or K coordination spheres in molecular mechanics or molecular dynamics studies.

  11. Generalizations of Brandl's theorem on Engel length

    Science.gov (United States)

    Quek, S. G.; Wong, K. B.; Wong, P. C.

    2013-04-01

    Let n Engel cycle generated by g and h. The length of the Engel cycle is m-n. A group G is said to have Engel length r, if all the length of the Engel cycles in G divides r. In this paper we discuss the Brandl's theorem on Engel length and give some of its generalizations.

  12. Integration of European Bond Markets

    DEFF Research Database (Denmark)

    Christiansen, Charlotte

    2014-01-01

    I investigate the time variation in the integration of EU government bond markets. The integration is measured by the explanatory power of European factor portfolios for the individual bond markets for each year. The integration of the government bond markets is stronger for EMU than non-EMU memb......-EMU members and stronger for old than new EU members. For EMU countries, the integration is weaker the lower the credit rating is. During the recent crisis periods, the integration is weaker, particularly for EMU countries....

  13. Roll bonding of strained aluminium

    DEFF Research Database (Denmark)

    Staun, Jakob M.

    2003-01-01

    This report investigates roll bonding of pre-strained (å ~ 4) aluminium sheets to produce high strain material from high purity aluminium (99.996%) and commercial pure aluminium (99.6%). The degree of bonding is investigated by optical microscopy and ultrasonic scanning. Under the right...... of the cross rolled volume fraction is found. To further asses this effect, and the anisotropy, it is necessary to acquire knowledge about both texture and microstructure, e.g. by TEM. Roll bonding of pre-strained aluminium is found to be a possible alternative to ARB in the quest for ultra-fine grained...

  14. Roll bonding of strained aluminium

    DEFF Research Database (Denmark)

    Staun, Jakob M.

    2003-01-01

    This report investigates roll bonding of pre-strained (å ~ 4) aluminium sheets to produce high strain material from high purity aluminium (99.996%) and commercial pure aluminium (99.6%). The degree of bonding is investigated by optical microscopy and ultrasonic scanning. Under the right...... of the cross rolled volume fraction is found. To further asses this effect, and the anisotropy, it is necessary to acquire knowledge about both texture and microstructure, e.g. by TEM. Roll bonding of pre-strained aluminium is found to be a possible alternative to ARB in the quest for ultra-fine grained...

  15. PRICING OF MULTIPLE DEFAULTABLE BOND

    Institute of Scientific and Technical Information of China (English)

    JianZhihong; LiChulin

    2002-01-01

    In this paper a generalized defaultable bond pricing formula is derived by assuming that there exists a defaultable forward rate term structure and that firms in the economy interact when default occurs. Generally,The risk-neutral default intensity χQ is not equal to the empirical or actual default intensity λ,. This paper proves that multiple default intensities are invari-ant under equivalent martingale transformation,given a well-diversified portfolio corresponding to the defaultable bond. Thus one can directly apply default intensities and fractional losses empirically estimated to the evaluation of defaultable bonds or contingent claims.

  16. The chemisorptive bond basic concepts

    CERN Document Server

    Clark, Alfred

    1974-01-01

    The Chemisorptive Bond: Basic Concepts describes the basic concepts of the chemisorptive bond on solid surfaces from the simple analogies with ordinary chemical bonds to the quantum-mechanical approaches.This book is composed of 10 chapters and begins with discussions of simple formulas for correlating measurable quantities in chemisorptions and catalysis. The succeeding chapters deal with theories based on quantum-mechanical principles that describe the mutual interactions of atoms of the solid and foreign atoms on the surface. The remaining chapters consider the possible arrangements

  17. Direct Bonded Pontic (Laporan Kasus

    Directory of Open Access Journals (Sweden)

    Suhandi Sidjaja

    2015-10-01

    Full Text Available Advanced science and technology in dentistry enable dental practitioners to modified she bonding techniques in tooth replacement. A pontic made of composite resin bonded to etched enamel of the adjacent teeth can be used in the replacement of one missing anterior tooth with a virgin or sowed adpicent tooth. The advantages of this technique include a one visit treatment, cow cost, good esthetics, less side effects and easy repair or rebounding. Clinical evaluation showed a high success rate therefore with a proper diagnosis and a perfect skill of the direct bonded technique this treatment can be used as an alternative restoration.

  18. A COMPARATIVE EVALUATION OF BOND - STRENGTH BETWEEN NORMAL DENTIN AND CARIES AFFECTED DENTIN: AN INVITRO STUDY

    Directory of Open Access Journals (Sweden)

    Arun

    2015-03-01

    Full Text Available INTRODUCTION: The concept of adhesive dentistry has taken leaps forward and has resulted in a concept of more conservation of tooth structure which in turn enhance the life of teeth. The bonding agent forms a hybrid layer with dentin and its other side co - polymerize with the matrix p hase of dental composite, producing strong micro - mechanical bonding. AIMS AND OBJECTIVE: To evaluate the bond strength of adhesive agent to normal dentin and caries affected dentin and also to compare the bond strength between different bonding agents. METHOD: 20 mandibular molar were collected, washed and stored in normal saline. Each tooth was cut longitudinally. Healthy tooth structure of each half of the tooth represents the control group and the carious portion of the same tooth represents as experi mental group. Thus, 80 samples were prepared. The groups were then further subdivided into 4 sub - groups of 4 different bonding agents. The dentin surface of all the sub groups were etched by 37% of phosphoric acid gel for 10 - 15 secs and respective bonding agent were used and cured for 20 secs. Cylindrical composite resin was prepared using a plastic module of internal diameter of 3mm and length 5mm. Statistical analysis was done using mean standard deviation (S.D, student ‘t’ test and level of significance ‘P’. RESULTS: For both the control and experimental group, 3M single bond has showed the strongest bond strength followed by Prime and Bond NT, Excite and PQ1.

  19. Quantum stability and magic lengths of metal atom wires

    Science.gov (United States)

    Cui, Ping; Choi, Jin-Ho; Lan, Haiping; Cho, Jun-Hyung; Niu, Qian; Yang, Jinlong; Zhang, Zhenyu

    2016-06-01

    Metal atom wires represent an important class of nanomaterials in the development of future electronic devices and other functional applications. Using first-principles calculations within density functional theory, we carry out a systematic study of the quantum stability of freestanding atom wires consisting of prototypical metal elements with s -, s p -, and s d -valence electrons. We explore how the quantum mechanically confined motion and local bonding of the valence electrons in these different wire systems can dictate their overall structural stability and find that the formation energy of essentially all the wires oscillates with respect to their length measured by the number n of atoms contained in the wires, establishing the existence of highly preferred (or magic) lengths. Furthermore, different wire classes exhibit distinctively different oscillatory characteristics and quantum stabilities. Alkali metal wires possessing an unpaired s valence electron per atom exhibit simple damped even-odd oscillations. In contrast, Al and Ga wires containing three s2p1 valence electrons per atom generally display much larger and undamped even-odd energy oscillations due to stronger local bonding of the p orbitals. Among the noble metals, the s -dominant Ag wires behave similarly to the linear alkali metal wires, while Au and Pt wires distinctly prefer to be structurally zigzagged due to strong relativistic effects. These findings are discussed in connection with existing experiments and should also be instrumental in future experimental realization of different metal atom wires in freestanding or supported environments with desirable functionalities.

  20. NMR properties of hydrogen-bonded glycine cluster in gas phase

    Science.gov (United States)

    Carvalho, Jorge R.; da Silva, Arnaldo Machado; Ghosh, Angsula; Chaudhuri, Puspitapallab

    2016-11-01

    Density Functional Theory (DFT) calculations have been performed to study the effect of the hydrogen bond formation on the Nuclear Magnetic Resonance (NMR) parameters of hydrogen-bonded clusters of glycine molecules in gas-phase. DFT predicted isotropic chemical shifts of H, C, N and O of the isolated glycine with respect to standard reference materials are in reasonable agreement with available experimental data. The variations of isotropic and anisotropic chemical shifts for all atoms constituting these clusters containing up to four glycine molecules have been investigated systematically employing gradient corrected hybrid B3LYP functional with three different types of extended basis sets. The clusters are mainly stabilized by a network of strong hydrogen bonds among the carboxylic (COOH) groups of glycine monomers. The formation of hydrogen bond influences the molecular structure of the clusters significantly which, on the other hand, gets reflected in the variations of NMR properties. The carbon (C) atom of the sbnd COOH group, the bridging hydrogen (H) and the proton-donor oxygen (O) atom of the Osbnd H bond suffer downfield shift due to the formation of hydrogen bond. The hydrogen bond lengths and the structural complexity of the clusters are found to vary with the number of participating monomers. A direct correlation between the hydrogen bond length and isotropic chemical shift of the bridging hydrogen is observed in all cases. The individual variations of the principal axis elements in chemical shift tensor provide additional insight about the different nature of the monomers within the cluster.

  1. 27 CFR 19.245 - Bonds and penal sums of bonds.

    Science.gov (United States)

    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—...

  2. 27 CFR 25.94 - Strengthening bonds.

    Science.gov (United States)

    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)...

  3. On the Correlation between the Blue Shift of Hydrogen Bonding and the Proton Donor-Proton Acceptor Distance

    Institute of Scientific and Technical Information of China (English)

    WANG,Jin-Ti(王金姼); FENG,Yong(封勇); LIU,Lei(刘磊); LI,Xiao-Song(李晓松); GUO,Qing-Xiang(郭庆祥)

    2004-01-01

    It is demonstrated that in all types of hydrogen bonds (X-H…Y) there is a balance between the long-range attractive orbital interactions and short-range Pauli/nucleus repulsions. When the proton acceptor approaches the proton donor from distance, the hydrogen bonding energy becomes more negative at relatively large distance, goes through a minimum, and then starts to become less negative when the short-range repulsive forces come into effect.Meanwhile, the X-H bond length increases at relatively large distances, goes through a maximum and starts to shorten when the short-range repulsive forces come into effect. Whether the hydrogen bond is red or blue shifted is dictated by the energy minimum position. If at the energy minimum position the X-H bond length is shorter than that for the free monomer, the hydrogen bond is blue shifted and vice versa. Further studies demonstrate that the recent report about the correlation of C-H bond lengths with proton donor-acceptor distance in F3C-H…OH2 and F3C-H…Cl- is not fully correct because the authors conducted an inappropriate comparison. Furthermore, it is shown for the first time that the Pauli/nucleus repulsion theory is applicable to the blue-shifted hydrogen bonds in the X-H…π complexes and the blue-shifted lithium bonds in the X-Li…Y complexes.

  4. Hydrogen bonding in tight environments

    DEFF Research Database (Denmark)

    Pirrotta, Alessandro; Solomon, Gemma C.; Franco, Ignacio

    2016-01-01

    The single-molecule force spectroscopy of a prototypical class of hydrogen-bonded complexes is computationally investigated. The complexes consist of derivatives of a barbituric acid and a Hamilton receptor that can form up to six simultaneous hydrogen bonds. The force-extension (F-L) isotherms...... of the host-guest complexes are simulated using classical molecular dynamics and the MM3 force field, for which a refined set of hydrogen bond parameters was developed from MP2 ab initio computations. The F-L curves exhibit peaks that signal conformational changes during elongation, the most prominent...... of which is in the 60-180 pN range and corresponds to the force required to break the hydrogen bonds. These peaks in the F-L curves are shown to be sensitive to relatively small changes in the chemical structure of the host molecule. Thermodynamic insights into the supramolecular assembly were obtained...

  5. Modified bonded bridge space maintainer.

    Science.gov (United States)

    Liegeois, F; Limme, M

    1999-01-01

    The premature loss of primary teeth can create the need for space maintenance and restoration of function. This article presents a fixed bonded space maintainer, which allows space to be maintained with economy of dental tissues.

  6. Weld bonding of stainless steel

    DEFF Research Database (Denmark)

    Santos, I. O.; Zhang, Wenqi; Goncalves, V.M.

    2004-01-01

    This paper presents a comprehensive theoretical and experimental investigation of the weld bonding process with the purpose of evaluating its relative performance in case of joining stainless steel parts, against alternative solutions based on structural adhesives or conventional spot...

  7. Adhesives for orthodontic bracket bonding

    Directory of Open Access Journals (Sweden)

    Déborah Daniella Diniz Fonseca

    2010-04-01

    Full Text Available The advent of acid etching, introduced by Buonocore in 1955, brought the possibility of bonding between the bracket base and enamel, contributing to more esthetic and conservative orthodontics. This direct bracket bonding technique has brought benefits such as reduced cost and time in performing the treatment, as well as making it easier to perform oral hygiene. The aim of this study was to conduct a survey of published studies on orthodontic bracket bonding to dental enamel. It was verified that resin composites and glass ionomer are the most studied and researched materials for this purpose. Resin-modified glass ionomer, with its biocompatibility, capacity of releasing fluoride and no need for acid etching on the tooth structure, has become increasingly popular among dentists. However, due to the esthetic and mechanical properties of light polymerizable resin composite, it continues to be one of the adhesives of choice in the bracket bonding technique and its use is widely disseminated.

  8. Effect of quantum nuclear motion on hydrogen bonding

    Energy Technology Data Exchange (ETDEWEB)

    McKenzie, Ross H., E-mail: r.mckenzie@uq.edu.au; Bekker, Christiaan [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia); Athokpam, Bijyalaxmi; Ramesh, Sai G. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)

    2014-05-07

    This work considers how the properties of hydrogen bonded complexes, X–H⋯Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O–H⋯O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 − 3.0 Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X–H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

  9. Effect of quantum nuclear motion on hydrogen bonding

    Science.gov (United States)

    McKenzie, Ross H.; Bekker, Christiaan; Athokpam, Bijyalaxmi; Ramesh, Sai G.

    2014-05-01

    This work considers how the properties of hydrogen bonded complexes, X-H⋯Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H⋯O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 - 3.0 Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X-H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

  10. DFT investigation on dihydrogen-bonded amine-borane complexes.

    Science.gov (United States)

    Yan, Shihai; Zou, Hongmei; Kang, Wukui; Sun, Lixiang

    2016-01-01

    The DFT method has been employed in the exploration on dihydrogen-bonded amine-borane complexes, with a special emphasis on the dimerization and substituent group effect. Stable dihydrogen bonded complexes can be generated from these amine-borane monomers with the appearance of NH(δ+)…H(δ-)B interactions. The binding energy decreases gradually with the increase of the steric effect of the substituents. The substituent group number mainly varies the C-N bond length. The dimerization generates close H…H and influences predominantly the N-B distance. The effect of dimerization on IR and vibrational circular dichroism (VCD) spectra is stronger than that of the number of substituent groups, which leads to distinct NBO charge variation on α-C. Both the substituent group number and dimerization enhance the chemical shift difference between hydrogen atoms covalently bonded to N and B, Δδ H-H, which can be hired as an index for structural determination. It is proposed that amine-borane complexes with more substituent groups in higher degree of polymerization are potentially interesting materials for hydrogen storage. Graphical Abstract Both the number of substituent group and dimerization enhance the chemical shift difference of hydrogen atoms covalently bonded on N and B, Δδ H-H, which can be employed as an index for the structural determination.

  11. O:H-O Bond Anomalous Relaxation Resolving Mpemba Paradox

    CERN Document Server

    Huang, Xi Zhang Yongli; Sun, Chang Q

    2013-01-01

    We demonstrate that the Mpemba paradox arises intrinsically from the release rate of energy initially stored in the covalent H-O part of the O:H-O bond in water albeit experimental conditions. Generally, heating raises the energy of a substance by lengthening and softening all bonds involved. However, the O:H nonbond in water follows actively the general rule of thermal expansion and drives the H-O covalent bond to relax oppositely in length and energy because of the inter-electron-electron pair coupling [J Phys Chem Lett 4, 2565 (2013); ibid 4, 3238 (2013)]. Heating stores energy into the H-O bond by shortening and stiffening it. Cooling the water as the source in a refrigerator as a drain, the H-O bond releases its energy at a rate that depends exponentially on the initially storage of energy, and therefore, Mpemba effect happens. This effect is formulated in terms of the relaxation time tau to represent all possible processes of energy loss. Consistency between predictions and measurements revealed that th...

  12. Performance of a nonempirical density functional on molecules and hydrogen-bonded complexes.

    Science.gov (United States)

    Mo, Yuxiang; Tian, Guocai; Car, Roberto; Staroverov, Viktor N; Scuseria, Gustavo E; Tao, Jianmin

    2016-12-21

    Recently, Tao and Mo derived a meta-generalized gradient approximation functional based on a model exchange-correlation hole. In this work, the performance of this functional is assessed on standard test sets, using the 6-311++G(3df,3pd) basis set. These test sets include 223 G3/99 enthalpies of formation, 99 atomization energies, 76 barrier heights, 58 electron affinities, 8 proton affinities, 96 bond lengths, 82 harmonic vibrational frequencies, 10 hydrogen-bonded molecular complexes, and 22 atomic excitation energies. Our calculations show that the Tao-Mo functional can achieve high accuracy for most properties considered, relative to the local spin-density approximation, Perdew-Burke-Ernzerhof, and Tao-Perdew-Staroverov-Scuseria functionals. In particular, it yields the best accuracy for proton affinities, harmonic vibrational frequencies, hydrogen-bond dissociation energies and bond lengths, and atomic excitation energies.

  13. Performance of a nonempirical density functional on molecules and hydrogen-bonded complexes

    Science.gov (United States)

    Mo, Yuxiang; Tian, Guocai; Car, Roberto; Staroverov, Viktor N.; Scuseria, Gustavo E.; Tao, Jianmin

    2016-12-01

    Recently, Tao and Mo derived a meta-generalized gradient approximation functional based on a model exchange-correlation hole. In this work, the performance of this functional is assessed on standard test sets, using the 6-311++G(3df,3pd) basis set. These test sets include 223 G3/99 enthalpies of formation, 99 atomization energies, 76 barrier heights, 58 electron affinities, 8 proton affinities, 96 bond lengths, 82 harmonic vibrational frequencies, 10 hydrogen-bonded molecular complexes, and 22 atomic excitation energies. Our calculations show that the Tao-Mo functional can achieve high accuracy for most properties considered, relative to the local spin-density approximation, Perdew-Burke-Ernzerhof, and Tao-Perdew-Staroverov-Scuseria functionals. In particular, it yields the best accuracy for proton affinities, harmonic vibrational frequencies, hydrogen-bond dissociation energies and bond lengths, and atomic excitation energies.

  14. Performance of a Nonempirical Density Functional on Molecules and Hydrogen-Bonded Complexes

    CERN Document Server

    Mo, Yuxiang; Car, Roberto; Staroverov, Viktor N; Scuseria, Gustavo E; Tao, Jianmin

    2016-01-01

    Recently, Tao and Mo (TM) derived a new meta-generalized gradient approximation based on a model exchange hole. In this work, the performance of this functional is assessed on standard test sets, using the 6-311++G(3df,3pd) basis set. These test sets include 223 G3/99 enthalpies of formation, 58 electron affinities, 8 proton affinities, 96 bond lengths, 82 harmonic vibrational frequencies, and 10 hydrogen-bonded molecular complexes. Our calculations show that the TM functional can achieve remarkable accuracy for most molecular properties, improving upon non-empirical density functionals considered here. In particular, it delivers the best accuracy for proton affinities, harmonic vibrational frequencies, and hydrogen-bonded dissociation energies and bond lengths, compared to other semilocal density-functional approximations considered in this work.

  15. Shear Bond Strength of Orthodontic Brackets Bonded to Zirconium Crowns

    Science.gov (United States)

    Mehmeti, Blerim; Azizi, Bleron; Kelmendi, Jeta; Iljazi-Shahiqi, Donika; Alar, Željko

    2017-01-01

    Background An increasing demand for esthetic restorations has resulted in an increased use of all-ceramic restorations, such as zirconium. However, one of the challenges the orthodontist must be willing to face is how to increase bond strength between the brackets and various ceramic restorations.Bond strength can beaffected bybracket type, by the material that bracketsaremade of, and their base surface design or retention mode. ​ Aim: of this study was to perform a comparative analysis of the shear bond strength (SBS) of metallic and ceramic orthodontic brackets bonded to all-zirconium ceramic surfaces used for prosthetic restorations, and also to evaluate the fracture mode of these two types of orthodontic brackets. Material and methods Twenty samples/semi-crowns of all-zirconium ceramic, on which orthodontic brackets were bonded, 10 metallic and 10 ceramic polycrystalline brackets, were prepared for this research. SBS has been testedby Universal Testing Machine, with a load applied using a knife edged rod moving at a fixed rate of 1 mm/min, until failure occurred. The force required to debond the brackets was recorded in Newton, then SBS was calculated to MPa. In addition, the samples were analyzed using a digital camera magnifier to determine Adhesive Remnant Index (ARI). Statistical data were processed using t-test, and the level of significance was set at α = 0.05. Results Higher shear bond strength values were observed in metallic brackets bonded to zirconium crowns compared tothoseof ceramic brackets, with a significant difference. During the test, two of the ceramic brackets were partially or totally damaged. Conclusion Metallic brackets, compared to ceramic polycrystalline brackets, seemed tocreate stronger adhesion with all-zirconium surfaces due to their better retention mode. Also, ceramic brackets showed higher fragility during debonding. PMID:28827846

  16. LAMMPS Framework for Directional Dynamic Bonding

    DEFF Research Database (Denmark)

    2012-01-01

    and bond types. When breaking bonds, all angular and dihedral interactions involving broken bonds are removed. The framework allows chemical reactions to be modeled, and use it to simulate a simplistic, coarse-grained DNA model. The resulting DNA dynamics illustrates the power of the present framework.......We have extended the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) to support directional bonds and dynamic bonding. The framework supports stochastic formation of new bonds, breakage of existing bonds, and conversion between bond types. Bond formation can be controlled...... to limit the maximal functionality of a bead with respect to various bond types. Concomitant with the bond dynamics, angular and dihedral interactions are dynamically introduced between newly connected triplets and quartets of beads, where the interaction type is determined from the local pattern of bead...

  17. Novel position-space renormalization group for bond directed percolation in two dimensions

    Science.gov (United States)

    Kaya, Hüseyin; Erzan, Ayşe

    A new position-space renormalization group approach is investigated for bond directed percolation in two dimensions. The threshold value for the bond occupation probabilities is found to be pc=0.6443. Correlation length exponents on time (parallel) and space (transverse) directions are found to be ν∥=1.719 and ν⊥=1.076, respectively, which are in very good agreement with the best-known series expansion results.

  18. Varying nanoparticle pseudostationary phase plug length during capillary electrophoresis†

    Science.gov (United States)

    Subramaniam, Varuni; Griffith, Lindsay; Haes, Amanda J.

    2016-01-01

    Capillary electrophoresis based separations of the hypothesized Parkinson’s disease biomarkers dopamine, epinephrine, pyrocatechol, L-3,4-dihydroxyphenylalanine (L-DOPA), glutathione, and uric acid are performed in the presence of a 1 nM 11-mercaptoundecanoic acid functionalized gold (Au@MUA) nanoparticle pseudostationary phase plug. Au@MUA nanoparticles are monitored in the capillary and remain stable in the presence of electrically-driven flow. Migration times, peak areas, and relative velocity changes (vs. no pseudostationary) are monitored upon varying (1) the Au@MUA nanoparticle pseudostationary phase plug length at a fixed separation voltage and (2) the separation voltage for a fixed Au@MUA nanoparticle pseudostationary phase plug length. For instance, the migration times of positively charged dopamine and epinephrine increase slightly as the nanoparticle pseudostationary phase plug length increases with concomitant decreases in peak areas and relative velocities as a result of attractive forces between the positively charged analytes and the negatively charged nanoparticles. Migration times for neutral pyrocatechol and slightly negative L-DOPA did not exhibit significant changes with increasing nanoparticle pseudostationary plug length; however, reduction in peak areas for these two molecules were evident and attributed to non-specific interactions (i.e. hydrogen bonding and van der Waals interactions) between the biomarkers and nanoparticles. Moreover, negatively charged uric acid and glutathione displayed progressively decreasing migration times and peak areas and as a result, increased relative velocities with increasing nanoparticle pseudostationary phase plug length. These trends are attributed to partitioning and exchanging with 11-mercaptoundecanoic acid on nanoparticle surfaces for uric acid and glutathione, respectively. Similar trends are observed when the separation voltage decreased thereby suggesting that nanoparticle-biomarker interaction

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

    Science.gov (United States)

    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

  20. Relaxation of the chemical bond skin chemisorption size matter ZTP mechanics H2O myths

    CERN Document Server

    Sun, Chang Q

    2014-01-01

    The aim of this book is to explore the detectable properties of a material to the parameters of bond and non-bond involved and to clarify the interdependence of various properties. This book is composed of four parts; Part I deals with the formation and relaxation dynamics of bond and non-bond during chemisorptions with uncovering of the correlation among the chemical bond, energy band, and surface potential barrier (3B) during reactions; Part II is focused on the relaxation of bonds between atoms with fewer neighbors than the ideal in bulk with unraveling of the bond order-length-strength (BOLS) correlation mechanism, which clarifies the nature difference between nanostructures and bulk of the same substance; Part III deals with the relaxation dynamics of bond under heating and compressing with revealing of rules on the temperature-resolved elastic and plastic properties of low-dimensional materials; Part IV is focused on the asymmetric relaxation dynamics of the hydrogen bond (O:H-O) and the anomalous behav...

  1. 27 CFR 26.69 - Strengthening bonds.

    Science.gov (United States)

    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....

  2. Reduced form models of bond portfolios

    OpenAIRE

    Matti Koivu; Teemu Pennanen

    2010-01-01

    We derive simple return models for several classes of bond portfolios. With only one or two risk factors our models are able to explain most of the return variations in portfolios of fixed rate government bonds, inflation linked government bonds and investment grade corporate bonds. The underlying risk factors have natural interpretations which make the models well suited for risk management and portfolio design.

  3. 27 CFR 24.146 - Bonds.

    Science.gov (United States)

    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...

  4. Welding, Bonding and Fastening, 1984

    Science.gov (United States)

    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.

  5. Information, polarization and term length in democracy

    DEFF Research Database (Denmark)

    Schultz, Christian

    2008-01-01

    This paper considers term lengths in a representative democracy where the political issue divides the population on the left-right scale. Parties are ideologically different and better informed about the consequences of policies than voters are. A short term length makes the government more accou...... the uncertainty is large and parties are not very polarized. Partisan voters always prefer a long term length. When politicians learn while in office a long term length becomes more attractive for swing voters....

  6. New Generalizations of Migdal-Kadanoff Bond-Moving Recursion Procedures and Their Applications

    Institute of Scientific and Technical Information of China (English)

    王春阳; 杨文献; 闫志伟; 杜红; 孔祥木; 张玉奇; 张凌宇

    2012-01-01

    Considering in symmetrical half-length bond operations,we present in this paper two types of newlydeveloped generalizations of the remarkable Migdal-Kadanoff bond-moving renormalization group transformation recursion procedures.The predominance in application of these generalized procedures are illustrated by making use of them to study the critical behavior of the spin-continuous Gaussian model constructed on the typical translational invariant lattices and fractals respectively.Results such as the correlation length critical exponents obtained by these means are found to be in good conformity with the classical results from other previous studies.

  7. Three methods to measure RH bond energies

    Energy Technology Data Exchange (ETDEWEB)

    Berkowitz, J. [Argonne National Lab., IL (United States); Ellison, G.B. [Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry; Gutman, D. [Catholic Univ. of America, Washington, DC (United States). Dept. of Chemistry

    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.

  8. Halogen Bonding in Organic Synthesis and Organocatalysis.

    Science.gov (United States)

    Bulfield, David; Huber, Stefan M

    2016-10-01

    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.

  9. 28 CFR 551.4 - Hair length.

    Science.gov (United States)

    2010-07-01

    ... to an inmate hair care services which comply with applicable health and sanitation requirements. ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Hair length. 551.4 Section 551.4 Judicial... Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and clean. (b)...

  10. String matching with variable length gaps

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Vildhøj, Hjalte Wedel

    2012-01-01

    We consider string matching with variable length gaps. Given a string T and a pattern P consisting of strings separated by variable length gaps (arbitrary strings of length in a specified range), the problem is to find all ending positions of substrings in T that match P. This problem is a basic...

  11. Repeated bonding of fixed retainer increases the risk of enamel fracture.

    Science.gov (United States)

    Chinvipas, Netrporn; Hasegawa, Yuh; Terada, Kazuto

    2014-01-01

    The aim of this study was to investigate the influences of repeated bonding, using 2 different orthodontic adhesive systems, on the shear bond strength (SBS) and the enamel surface morphology. Sixty premolars were divided into 2 groups (n = 30), and either Transbond XT (T group) or Fuji Ortho LC (F group) adhesives were used. SBS was measured 24 h after bonding, using a universal testing machine. Then, the enamel surfaces were investigated and the mode of failure was described using adhesive remnant index (ARI) scores. After each debonding, 10 teeth from each group were examined by scanning electron microscopy to determine the penetration of adhesives, the length of resin tags, and the state of the enamel surface. The other teeth were subjected to two more bonding/debonding procedures. In T group, the second debonding sequences had significantly higher bond strengths than the other sequences. The length of resin tags was greatest in the second debonding sequence, although there was no significant difference. In F group, the SBS increased with further rebonding and the failure mode tended towards cohesive failure. In both groups, the ARI scores increased with rebonding. Enamel loss could have occurred with both adhesives, although the surfaces appeared unchanged to the naked eye. From this study, we suggest that enamel damage caused by repeated bonding is of concern. To prevent bond failure, we should pay attention to the adhesion method used for bondable retainers.

  12. Effects of hydrogen bond on 2-aminopyridine and its derivatives complexes in methanol solvent.

    Science.gov (United States)

    Zhao, Jinfeng; Song, Peng; Cui, Yanling; Liu, Xuemei; Sun, Shaowu; Hou, Siyao; Ma, Fengcai

    2014-10-15

    In the present work, the time-dependent density functional theory (TD-DFT) method was adopted to investigate the excited state hydrogen-bond dynamics of 2-aminopyridine monomer (2AP) and its derivatives in hydrogen donating methanol solvent. The calculated steady-state absorption and fluorescence spectra agree well with the experimental results. Theoretical results state that the bond lengths of both O-H and N-H bands are lengthened, while the intermolecular hydrogen bond lengths are shortened in the excited state. Further, the intermolecular hydrogen bonds are proved to be strengthened according to the calculated binding energy. As a reasonable explanation, the hydrogen bonds binding energy increases with multiple hydrogen-bonding interactions in the electronically excited state. In addition, the hydrogen bonding dynamics in the excited state were visualized by the spectral shifts of vibrational modes. The calculated infrared spectra of both O-H and N-H stretching vibrational regions revealed that the O-H and N-H stretching bands red-shift.

  13. Vibrational analysis on the revised potential energy curve of the low-barrier hydrogen bond in photoactive yellow protein

    Directory of Open Access Journals (Sweden)

    Yusuke Kanematsu

    2016-01-01

    Full Text Available Photoactive yellow protein (PYP has a characteristic hydrogen bond (H bond between p-coumaric acid chromophore and Glu46, whose OH bond length has been observed to be 1.21 Å by the neutron diffraction technique [Proc. Natl. Acad. Sci. 106, 440–4]. Although it has been expected that such a drastic elongation of the OH bond could be caused by the quantum effect of the hydrogen nucleus, previous theoretical computations including the nuclear quantum effect have so far underestimated the bond length by more than 0.07 Å. To elucidate the origin of the difference, we performed a vibrational analysis of the H bond on potential energy curve with O…O distance of 2.47 Å on the equilibrium structure, and that with O…O distance of 2.56 Å on the experimental crystal structure. While the vibrationally averaged OH bond length for equilibrium structure was underestimated, the corresponding value for crystal structure was in reasonable agreement with the corresponding experimental values. The elongation of the O…O distance by the quantum mechanical or thermal fluctuation would be indispensable for the formation of a low-barrier hydrogen bond in PYP.

  14. FATHER, SOCIAL BOND AND WOMEN

    Directory of Open Access Journals (Sweden)

    SYLVIA DE CASTRO KORGI

    2006-05-01

    Full Text Available On the cross-point of two of the most important and inseparable Freudian questions: What is a father?and, What a woman wants?, this paper begins a reflection about the women’s place in the Freudianarticulation of the relationship between the father and the social bond. In fact, the Freudian father, thanksto the law mediation which he is its agent, has as a function the regulation of the pleasure that participatesin the social bond, making this way possible the human community. On the other hand, the support ofthe human community is the bond among brothers, as well as Freud presents it in his foundational textof the Law. How to precise the women’s place in this arrangement? The reflection stands out this thatexceeds the Father’s Law and that Freud sets on women’s account, initially under the figure of heropposition to the culture.

  15. Two Comments on Bond Angles

    Science.gov (United States)

    Glaister, P.

    1997-09-01

    Tetrahedral Bond Angle from Elementary Trigonometry The alternative approach of using the scalar (or dot) product of vectors enables the determination of the bond angle in a tetrahedral molecule in a simple way. There is, of course, an even more straightforward derivation suitable for students who are unfamiliar with vectors, or products thereof, but who do know some elementary trigonometry. The starting point is the figure showing triangle OAB. The point O is the center of a cube, and A and B are at opposite corners of a face of that cube in which fits a regular tetrahedron. The required bond angle alpha = AÔB; and using Pythagoras' theorem, AB = 2(square root 2) is the diagonal of a face of the cube. Hence from right-angled triangle OEB, tan(alpha/2) = (square root 2) and therefore alpha = 2tan-1(square root 2) is approx. 109° 28' (see Fig. 1).

  16. Bond percolation on multiplex networks

    CERN Document Server

    Hackett, A; Gómez, S; Arenas, A; Gleeson, J P

    2015-01-01

    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 multipex network constructed from London rail and Eu...

  17. Ab initio path integral molecular dynamics simulation study on the dihydrogen bond of NH4+⋯BeH2

    Science.gov (United States)

    Hayashi, Aiko; Shiga, Motoyuki; Tachikawa, Masanori

    2005-07-01

    An ab initio path integral molecular dynamics simulation has been performed to study the quantum and thermal effects of a dihydrogen bonded cation, NH4+⋯BeH2. In this system, an attractive interaction exists between two neighboring hydrogen atoms as N δ- H δ+ ⋯H δ- Be δ+ involving large-amplitude of vibration. Some properties playing a key role for this dihydrogen bonded system, such as the bond length, bond angle, and distribution of atomic charges, are investigated in detail by comparing the results of path integral and classical molecular dynamics with those of the equilibrium structure. It was found that the atomic charges of H δ+ and H δ- are decreased and the dihydrogen H δ+ ⋯H δ- bond length is expanded as the thermal and zero-point quantum effects.

  18. Anodic bonding using a hybrid electrode with a two-step bonding process

    Science.gov (United States)

    Wei, Luo; Jing, Xie; Yang, Zhang; Chaobo, Li; Yang, Xia

    2012-06-01

    A two-step bonding process using a novel hybrid electrode is presented. The effects of different electrodes on bonding time, bond strength and the bonded interface are analyzed. The anodic bonding is studied using a domestic bonding system, which carries out a detailed analysis of the integrity of the bonded interface and the bond strength measurement. With the aid of the hybrid electrode, a bubble-free anodic bonding process could be accomplished within 15-20 min, with a shear strength in excess of 10 MPa. These results show that the proposed method has a high degree of application value, including in most wafer-level MEMS packaging.

  19. Optimal Investment in Structured Bonds

    DEFF Research Database (Denmark)

    Jessen, Pernille; Jørgensen, Peter Løchte

    2012-01-01

    and consider different utility functions and trading strategies. Our results show that investors should include structured bonds in their optimal portfolio only if they cannot access the index underlying the option directly and only if the products then provide sufficient diversification to compensate......Retail structured products regularly receive much criticism from financial experts but seem to remain popular with investors. This article considers a generic structured product: the principal-protected index-linked note (structured bond), which resembles a portfolio insurance contract. The purpose...

  20. BOND ORDERING IN NONCRYSTALLINE SOLIDS

    OpenAIRE

    Revesz, A.

    1982-01-01

    From the analysis of optical properties of noncrystalline (nc) and the corresponding crystalline solids with predominantly covalent bonds a bonding order parameter, F, is derived. This parameter reveals differences between nc solids which are characterized by similar degree of short-range-order as, e.g., amorphous Si (F ≤ 0.8) and vitreous SiO2 (F ≈ 1). Both the optical and electrical properties indicate that, in contrast to amorphous solids, the electronic states in vitreous solids may remai...

  1. Performance bond: conditional or unconditional

    OpenAIRE

    Supardi, Azizan; Yaakob, Jamaluddin; Adnan, Hamimah

    2009-01-01

    In construction contracts, a 'performance bond' is a bond taken out by the contractor, usually with a bank or insurance company (in return for payment of a premium), for the benefit of and at the request of the employer, in a stipulated maximum sum of liability and enforceable by the employer in the event of the contractor's default, repudiation or insolvency, as stated by Nigel M Robinson et. al. in his book, Construction Law in Singapore and Malaysia. He further added that there are two typ...

  2. Anodically bonded submicron microfluidic chambers.

    Science.gov (United States)

    Dimov, S; Bennett, R G; Córcoles, A; Levitin, L V; Ilic, B; Verbridge, S S; Saunders, J; Casey, A; Parpia, J M

    2010-01-01

    We demonstrate the use of anodic bonding to fabricate cells with characteristic size as large as 7 x 10 mm(2), with height of approximately 640 nm, and without any internal support structure. The cells were fabricated from Hoya SD-2 glass and silicon wafers, each with 3 mm thickness to maintain dimensional stability under internal pressure. Bonding was carried out at 350 degrees C and 450 V with an electrode structure that excluded the electric field from the open region. We detail fabrication and characterization steps and also discuss the design of the fill line for access to the cavity.

  3. Anodically bonded submicron microfluidic chambers

    Science.gov (United States)

    Dimov, S.; Bennett, R. G.; Córcoles, A.; Levitin, L. V.; Ilic, B.; Verbridge, S. S.; Saunders, J.; Casey, A.; Parpia, J. M.

    2010-01-01

    We demonstrate the use of anodic bonding to fabricate cells with characteristic size as large as 7×10 mm2, with height of ≈640 nm, and without any internal support structure. The cells were fabricated from Hoya SD-2 glass and silicon wafers, each with 3 mm thickness to maintain dimensional stability under internal pressure. Bonding was carried out at 350 °C and 450 V with an electrode structure that excluded the electric field from the open region. We detail fabrication and characterization steps and also discuss the design of the fill line for access to the cavity.

  4. NDT evaluation of long-term bond durability of CFRP-structural systems applied to RC highway bridges

    Science.gov (United States)

    Crawford, Kenneth C.

    2016-06-01

    The long-term durability of CFRP structural systems applied to reinforced-concrete (RC) highway bridges is a function of the system bond behavior over time. The sustained structural load performance of strengthened bridges depends on the carbon fiber-reinforced polymer (CFRP) laminates remaining 100 % bonded to concrete bridge members. Periodic testing of the CFRP-concrete bond condition is necessary to sustain load performance. The objective of this paper is to present a non-destructive testing (NDT) method designed to evaluate the bond condition and long-term durability of CFRP laminate (plate) systems applied to RC highway bridges. Using the impact-echo principle, a mobile mechanical device using light impact hammers moving along the length of a bonded CFRP plate produces unique acoustic frequencies which are a function of existing CFRP plate-concrete bond conditions. The purpose of this method is to test and locate CFRP plates de-bonded from bridge structural members to identify associated deterioration in bridge load performance. Laboratory tests of this NDT device on a CFRP plate bonded to concrete with staged voids (de-laminations) produced different frequencies for bonded and de-bonded areas of the plate. The spectra (bands) of frequencies obtained in these tests show a correlation to the CFRP-concrete bond condition and identify bonded and de-bonded areas of the plate. The results of these tests indicate that this NDT impact machine, with design improvements, can potentially provide bridge engineers a means to rapidly evaluate long lengths of CFRP laminates applied to multiple highway bridges within a national transportation infrastructure.

  5. Observation of water dangling OH bonds around dissolved nonpolar groups.

    Science.gov (United States)

    Perera, P N; Fega, K R; Lawrence, C; Sundstrom, E J; Tomlinson-Phillips, J; Ben-Amotz, Dor

    2009-07-28

    We report the experimental observation of water dangling OH bonds in the hydration shells around dissolved nonpolar (hydrocarbon) groups. The results are obtained by combining vibrational (Raman) spectroscopy and multivariate curve resolution (MCR), to reveal a high-frequency OH stretch peak arising from the hydration shell around nonpolar (hydrocarbon) solute groups. The frequency and width of the observed peak is similar to that of dangling OH bonds previously detected at macroscopic air-water and oil-water interfaces. The area of the observed peak is used to quantify the number of water dangling bonds around hydrocarbon chains of different length. Molecular dynamics simulation of the vibrational spectra of water molecules in the hydration shell around neopentane and benzene reveals high-frequency OH features that closely resemble the experimentally observed dangling OH vibrational bands around neopentyl alcohol and benzyl alcohol. The red-shift of approximately 50 cm(-1) induced by aromatic solutes is similar to that previously observed upon formation of a pi-H bond (in low-temperature benzene-water clusters).

  6. Essays on European bond markets

    NARCIS (Netherlands)

    Cheung, Y.C.

    2005-01-01

    This dissertation focused on a number of issues that are of importance in the current European bond market. In the past years, the fiscal policy of the Eurozone members, advances in the technology of trading platforms and the introduction of a single currency have reshaped the fixed income markets

  7. Essays on European bond markets

    NARCIS (Netherlands)

    Cheung, Y.C.

    2005-01-01

    This dissertation focused on a number of issues that are of importance in the current European bond market. In the past years, the fiscal policy of the Eurozone members, advances in the technology of trading platforms and the introduction of a single currency have reshaped the fixed income markets i

  8. Non-bonded ultrasonic transducer

    Science.gov (United States)

    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.

  9. On double bonds in fullerenes

    Directory of Open Access Journals (Sweden)

    Stepenshchikov D. G.

    2016-03-01

    Full Text Available Various distributions of double carbon bonds in the fullerenes have been considered in the paper from the point that they are absent in the pentagonal rings. The appropriate classification of the fullerenes has been built. The results may be used when modeling the fullerenes of a given topology and calculating their physical-chemical properties

  10. Bonding Elastomers To Metal Substrates

    Science.gov (United States)

    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.

  11. Machine Gun Liner Bond Strength

    Science.gov (United States)

    2007-08-01

    explosive bonding of pure tantalum, several tantalum alloys, and Stellite 25 (an alloy of cobalt, chrome , nickel, and tungsten) in a liner...Difficulties have been experienced in machining an explosively- clad tantalum alloy in an M242 Bushmaster barrel [6].) One disadvantage of Stellite 25 was

  12. Application of the bond valence method in the non-isovalent semiconductor alloy (GaN)1-x(ZnO)x

    Science.gov (United States)

    Liu, Jian

    2016-10-01

    This paper studies the bond valence method (BVM) and its application in the non-isovalent semiconductor alloy (GaN)1-x(ZnO)x. Particular attention is paid to the role of short-range order (SRO). The theoretical standing of the BVM is examined by density-functional theory (DFT) calculations. Combining the BVM with Monte-Carlo simulations and a DFT-based cluster expansion model, bond-length distributions and bond-angle variations are predicted. The connection between bond valence and bond stiffness is also discussed. Finally the BVM is extended to the modelling of an interatomic potential.

  13. Inheritance of telomere length in a bird.

    Directory of Open Access Journals (Sweden)

    Thorsten Horn

    Full Text Available Telomere dynamics are intensively studied in human ageing research and epidemiology, with many correlations reported between telomere length and age-related diseases, cancer and death. While telomere length is influenced by environmental factors there is also good evidence for a strong heritable component. In human, the mode of telomere length inheritance appears to be paternal and telomere length differs between sexes, with females having longer telomeres than males. Genetic factors, e.g. sex chromosomal inactivation, and non-genetic factors, e.g. antioxidant properties of oestrogen, have been suggested as possible explanations for these sex-specific telomere inheritance and telomere length differences. To test the influence of sex chromosomes on telomere length, we investigated inheritance and sex-specificity of telomere length in a bird species, the kakapo (Strigops habroptilus, in which females are the heterogametic sex (ZW and males are the homogametic (ZZ sex. We found that, contrary to findings in humans, telomere length was maternally inherited and also longer in males. These results argue against an effect of sex hormones on telomere length and suggest that factors associated with heterogamy may play a role in telomere inheritance and sex-specific differences in telomere length.

  14. 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

    Science.gov (United States)

    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

  15. Measuring the energy landscape of complex bonds using AFM

    Science.gov (United States)

    Mayyas, Essa; Hoffmann, Peter; Runyan, Lindsay

    2009-03-01

    We measured rupture force of a complex bond of two interacting proteins with atomic force microscopy. Proteins of interest were active and latent Matrix metalloproteinases (MMPs), type 2 and 9, and their tissue inhibitors TIMP1 and TIMP2. Measurements show that the rupture force depends on the pulling speed; it ranges from 30 pN to 150 pN at pulling speeds 30nm/s to 48000nm/s. Analyzing data using an extended theory enabled us to understand the mechanism of MMP-TIMP interaction; we determined all physical parameters that form the landscape energy of the interaction, in addition to the life time of the bond and its length. Moreover, we used the pulling experiment to study the interaction of TIMP2 with the receptor MT1-MMP on the surface of living cells.

  16. Contribution of Hydrogen Bonds to Paper Strength Properties.

    Directory of Open Access Journals (Sweden)

    Piotr Przybysz

    Full Text Available The objective of this work was to investigate the influence of hydrogen bonds between fibres on static and dynamic strength properties of paper. A commercial bleached pinewood kraft pulp was soaked in water, refined in a PFI, and used to form paper webs in different solvents, such as water, methanol, ethanol, n-propanol and n-butanol, to determine the effect of their dipole moment on static and dynamic strength properties of resulting paper sheets. Paper which was formed in water, being the solvent of the highest dipole moment among the tested ones, showed the highest breaking length and tear resistance. When paper webs were formed in n-butanol, which was the least polar among the solvents, these parameters were reduced by around 75%. These results provide evidence of the importance of water in paper web formation and strong impact of hydrogen bonds between fibres on strength properties of paper.

  17. The interplay of thiophilic and hydrogen bonding interactions in the supramolecular architecture of phenylmercury 4-hydroxypiperidine dithiocarbamate

    Science.gov (United States)

    Prasad, Rajendra; Yadav, Reena; Trivedi, Manoj; Kociok-Köhn, Gabriele; Kumar, Abhinav

    2016-01-01

    A new phenylmercury(II) dithiocarbamate complex [PhHg(S2CN(CH2)4CH(OH)], (1) has been synthesized and characterized by elemental analyses, IR, 1H and 13C NMR spectroscopy and X-ray crystallography. The crystal structure of 1 shows a linear arrangement at the Hg(II) centre of the molecule through bonding of the sulphur atom of the dithiocarbamate ligand and the carbon atom of the aromatic ring. Weak intermolecular thiophilic Hg···S interactions lead to a "head-to-tail" dimer and the presence of a hydroxyl group at the periphery of piperidine moiety generates a 1D-chain network through intermolecular O···H interactions. The nature of weak intra- and intermolecular Hg···S, H···S and intermolecular O···H interactions have been assessed with the help of ab initio calculations and atoms-in-molecules (AIM) approach.

  18. Method for fusion bonding thermoplastic composites

    Energy Technology Data Exchange (ETDEWEB)

    Benatar, A.; Gutowski, T.G.

    1986-10-01

    Bonding of thermoplastic composites is a critical step in the manufacture of aerospace structures. The objective of this project is to investigate different methods for fusion bonding thermoplastic composites quickly, with a good bond strength, and without warping and deconsolidation. This is best accomplished by heating and melting the thermoplastic on the bond surface only, and then pressing the parts together for a fusion bond. For this purpose, a variety of surface heating techniques were examined for bonding of PEEK and J Polymer composites. These included: resistance heating, infrared heating, induction heating, dielectric/microwave heating, and ultrasonic welding. 20 references, 10 figures, 1 table.

  19. Why Static O-H Bond Parameters Cannot Characterize the Free Radical Scavenging Activity of Phenolic Antioxidants: ab initio Study

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The static O-H bond parameters including O-H bond length, O-H charge difference, O-H Mulliken population and O-H bond stretching force constant (k) for 17 phenols were calculated by ab initio method HF/6-31G**. In combination with the O-H bond dissociation enthalpies (BDE) of the phenols determined by experiment, it was found that there were poor correlationships between the static O-H bond parameters and O-H BDE. Considering the good correlationship between O-H BDE and logarithm of free radical scavenging rate constant for phenolic antioxidant, it is reasonable to believe that the ineffectiveness of static O-H bond parameters in characterizing antioxidant activity arises from the fact that they cannot measure the O-H BDE.

  20. Strength of Bond Covenants and Bond Assessment Framework

    Directory of Open Access Journals (Sweden)

    Noel Yahanpath

    2012-06-01

    Full Text Available We examine bond covenants of 29 New Zealand bond issues between 2001 and 2007.Results from the study indicate that protection provided for bondholders is weak and limited.On average, only 2-3 types of covenants are embedded with the issues and only 27% of thesecovenants provide full protection to the bondholders. However, bondholders are not compensated for taking the additional risk. We propose an alternative assessment framework that directly assesses the level of protection offered to bondholders. We calculate thecovenant quality score for the issues and classify them into four levels of protection: very high protection, moderate, low and very low. Recent legislative changes will go some way towards improving investor protection and confidence, but the effect is yet to be seen. This proposed scoring framework can be used by potential investors to complement the traditional credit ratings when making their investment decisions.

  1. Axial Globe Length in Congenital Ptosis.

    Science.gov (United States)

    Takahashi, Yasuhiro; Kang, Hyera; Kakizaki, Hirohiko

    2015-01-01

    To compare axial globe length between affected and unaffected sides in patients with unilateral congenital ptosis. This prospective observational study included 37 patients (age range: 7 months to 58 years). The axial globe length, margin reflex distance-1 (MRD-1), and refractive power were measured. The axial globe length difference was calculated by subtracting the axial globe length on the unaffected side from that of the affected side. The relationships among axial globe length differences, MRD-1 on the affected sides, and patient ages were analyzed using multiple regression analysis. No significant differences were found in the axial globe length between sides (P = .677). The axial globe length difference was 0.17 ± 0.30 mm (mean ± standard deviation), and two patients (5.4%), aged 32 to 57 years, showed axial globe length more than 0.67 mm longer (corresponding to a refractive power of 2 diopters) on the affected side compared to the unaffected side. The multiple regression model between axial globe length difference, patient age, and MRD-1 on the affected sides was less appropriate (YAGL = 0.003XAGE-0.048XMRD-1 +0.112; r = 0.338; adjusted r2 = 0.062; P = .127). The cylindrical power was greater on the affected side (P = .046), although the spherical power was not different between sides (P = .657). No significant difference was identified in the axial globe length between sides, and only 5% of non-pediatric patients showed an axial globe length more than 0.67 mm longer on the affected side. Congenital ptosis may have little effect on axial globe length elongation, and the risk of axial myopia-induced anisometropic amblyopia may be low in patients with unilateral congenital ptosis. Copyright 2015, SLACK Incorporated.

  2. Diabetes mellitus and the eye: axial length

    OpenAIRE

    Huntjens, B.; O’Donnell, C.

    2006-01-01

    Background and aims: The refractive error of the eye is dependent on its axial length. Refractive error is known to fluctuate significantly in poorly controlled diabetic patients. Recently it has been reported that human eyes fluctuate in axial length during the day. However, this change is not detectable in all subjects, suggesting physiological influences such as diet. The purpose of this study was to investigate fluctuations in axial length and blood glucose levels (BGLs) in diabetic patie...

  3. Fibonacci Lengths of Certain Nilpotent 2-Groups

    Institute of Scientific and Technical Information of China (English)

    H. DOOSTIE; A. T. ADNANI

    2007-01-01

    In this paper, we study two classes of 2-generated 2-groups of nilpotency class 2 classified by Kluempen in 2002 and also a class of finite 2-groups of high nilpotency class for their Fibonacci lengths.Their involvement in certain interesting sequences of Tribonacci numbers gives us some explicit formulas for the Fibonacci lengths and this adds to the small class of finite groups for which the Fibonacci length are known.

  4. Large Slip Length over a Nanopatterned Surface

    Institute of Scientific and Technical Information of China (English)

    LI Ding; DI Qin-Feng; LI Jing-Yuan; QIAN Yue-Hong; FANG Hai-Ping

    2007-01-01

    A thermodynamic method is employed to analyse the slip length of hydrophobic nanopatterned surface.The maximal slip lengths with respect to the hydrophobicity of the nanopatterned surface are computed.It is found that the slip length reaches more than 50μm if the nanopatterned surfaces have a contact angle larger than 160°.Such results are expected to find extensive applications in micro-channels and helpful to understand recent experimental observations of the slippage of nanopatterned surfaces.

  5. Dither Cavity Length Controller with Iodine Locking

    Directory of Open Access Journals (Sweden)

    Lawson Marty

    2016-01-01

    Full Text Available A cavity length controller for a seeded Q-switched frequency doubled Nd:YAG laser is constructed. The cavity length controller uses a piezo-mirror dither voltage to find the optimum length for the seeded cavity. The piezo-mirror dither also dithers the optical frequency of the output pulse. [1]. This dither in optical frequency is then used to lock to an Iodine absorption line.

  6. New length operator for loop quantum gravity

    CERN Document Server

    Ma, Yongge; Yang, Jinsong

    2010-01-01

    An alternative expression for the length operator in loop quantum gravity is presented. The operator is background-independent, symmetric, positive semi-definite, and well-defined on the kinematical Hilbert space. The expression for the regularized length operator can moreover be understood both from a simple geometrical perspective as the average of a formula relating the length to area, volume and flux operators, and also consistently as the result of direct substitution of the densitized triad operator with the functional derivative operator into the regularized expression of the length. Both these derivations are discussed, and the origin of an undetermined overall factor in each case is also elucidated.

  7. On the attached length of orifices

    Science.gov (United States)

    Komkin, A. I.; Mironov, M. A.; Yudin, S. I.

    2012-11-01

    The attached length of orifices in reactive mufflers has been estimated based on numerical calculations by the finite-element method. The numerical results for a diaphragm in a duct are compared with the theoretical data obtained by Rayleigh, Fock, Karal, and Ingard. The dependence of the attached length on the diaphragm thickness is given. The results obtained are generalized for the case in which the orifice is a Helmholtz resonator neck. The effect of the resonator length on the attached length of the neck is analyzed.

  8. Mouse gestation length is genetically determined.

    Directory of Open Access Journals (Sweden)

    Stephen A Murray

    Full Text Available BACKGROUND: Preterm birth is an enormous public health problem, affecting over 12% of live births and costing over $26 billion in the United States alone. The causes are complex, but twin studies support the role of genetics in determining gestation length. Despite widespread use of the mouse in studies of the genetics of preterm birth, there have been few studies that actually address the precise natural gestation length of the mouse, and to what degree the timing of labor and birth is genetically determined. METHODOLOGY/PRINCIPAL FINDINGS: To further develop the mouse as a genetic model of preterm birth, we developed a high-throughput monitoring system and measured the gestation length in 15 inbred strains. Our results show an unexpectedly wide variation in overall gestation length between strains that approaches two full days, while intra-strain variation is quite low. Although litter size shows a strong inverse correlation with gestation length, genetic difference alone accounts for a significant portion of the variation. In addition, ovarian transplant experiments support a primary role of maternal genetics in the determination of gestation length. Preliminary analysis of gestation length in the C57BL/6J-Chr#(A/J/NaJ chromosome substitution strain (B.A CSS panel suggests complex genetic control of gestation length. CONCLUSIONS/SIGNIFICANCE: Together, these data support the role of genetics in regulating gestation length and present the mouse as an important tool for the discovery of genes governing preterm birth.

  9. Bond strength of cementitious borehole plugs in welded tuff

    Energy Technology Data Exchange (ETDEWEB)

    Akgun, H.; Daemen, J.J.K. [Arizona Univ., Tucson, AZ (USA). Dept. of Mining and Geological Engineering

    1991-02-01

    Axial loads on plugs or seals in an underground repository due to gas, water pressures and temperature changes induced subsequent to waste and plug emplacement lead to shear stresses at the plug/rock contact. Therefore, the bond between the plug and rock is a critical element for the design and effectiveness of plugs in boreholes, shafts or tunnels. This study includes a systematic investigation of the bond strength of cementitious borehole plugs in welded tuff. Analytical and numerical analysis of borehole plug-rock stress transfer mechanics is performed. The interface strength and deformation are studied as a function of Young`s modulus ratio of plug and rock, plug length and rock cylinder outside-to-inside radius ratio. The tensile stresses in and near an axially loaded plug are analyzed. The frictional interface strength of an axially loaded borehole plug, the effect of axial stress and lateral external stress, and thermal effects are also analyzed. Implications for plug design are discussed. The main conclusion is a strong recommendation to design friction plugs in shafts, drifts, tunnels or boreholes with a minimum length to diameter ratio of four. Such a geometrical design will reduce tensile stresses in the plug and in the host rock to a level which should minimize the risk of long-term deterioration caused by excessive tensile stresses. Push-out tests have been used to determine the bond strength by applying an axial load to cement plugs emplaced in boreholes in welded tuff cylinders. A total of 130 push-out tests have been performed as a function of borehole size, plug length, temperature, and degree of saturation of the host tuff. The use of four different borehole radii enables evaluation of size effects. 119 refs., 42 figs., 20 tabs.

  10. Shear bond strength of two resin cements to human root dentin using three dentin bonding agents.

    Science.gov (United States)

    Gogos, C; Stavrianos, C; Kolokouris, I; Economides, N; Papadoyannis, I

    2007-01-01

    This study compared the bond strength of two resin cements to human root dentin when used with three bonding agents. The materials used were Rely X ARC and Perma Cem, two one-bottle bonding agents (Single Bond, Bond-1) and one self-etching bonding agent (Clearfil SE Bond). The dentin was obtained from single rooted human teeth, and the specimens were treated with either 15% EDTA or 37% phosphoric acid to remove the smear layer, except in groups where the self-etching bonding agent was used. The resin cements were placed on dentin surfaces with the use of bonding agents. Shear bond strength (SBS) was tested using a single plane shear test assembly. The dentin specimens were divided into 10 groups. Eight groups were pre-treated with EDTA or phosphoric acid to remove the smear layer, followed by a bonding agent (Bond-1 or Single Bond) and resin cement (Rely X or Perma Cem). In the two remaining groups, the smear layer was left intact, and the two resins cements were used in combination with the self-etching bonding agent (Clearfil SE Bond). No statistically significant differences were observed among the eight groups treated with one-bottle bonding agents. The mean bond strengths of the two groups treated with the self-etching bonding agent did not differ significantly from each other but were both significantly greater than the bond strengths of all the other groups. The results of this study also showed that EDTA can be used as an alternative to phosphoric acid in bonding procedures for resin cements. However, the bond strengths of resin cements, in combination with a self-etching bonding agent, were significantly greater than those of the same cements when used with one-bottle bonding agents.

  11. Locking a molecular bond: A case study of CsI

    DEFF Research Database (Denmark)

    Szakács, Tamás; Amstrup, Bjarne; Gross, Peter

    1994-01-01

    This paper treats the problem of locking a molecular bond at a length other than the equilibrium distance, with the help of optical electric fields. Locking conditions for single-color fields are examined, and slowly decaying locked wave functions are sought. These were functions are then used as...

  12. Effect of Hydrogen Bonding on Linear and Nonlinear Rheology of Entangled Polymer Melts

    DEFF Research Database (Denmark)

    Shabbir, Aamir; Goldansaz, Hadi; Hassager, Ole

    2015-01-01

    . The number of AA side groups (hydrogen-bonding groups) after hydrolysis is determined from NMR measurements. We show that using the theoretical dependency of modulus and reptation time on the packing length, we can account for the changes in linear viscoelasticity due to transformation of nBA side groups...

  13. Better the devil you know: common terns stay with a previous partner although pair bond duration

    DEFF Research Database (Denmark)

    Rebke, Maren; Becker, Peter H; Colchero, Fernando

    2016-01-01

    In a monogamous species two partners contribute to the breeding process. We study pair formation as well as the effect of pair bond length and age on breeding performance, incorporating individual heterogeneity, based on a high quality dataset of a long-lived seabird, the common tern (Sterna hiru...

  14. Self-assembled structures in diblock copolymers with hydrogen-bonded amphiphilic plasticizing compounds

    NARCIS (Netherlands)

    Valkama, Sami; Ruotsalainen, Teemu; Nykanen, Antti; Laiho, Ari; Kosonen, Harri; ten Brinke, Gerrit; Ikkala, Olli; Ruokolainen, Janne; Nykänen, Antti

    2006-01-01

    Hydrogen-bonding amphiphilic low molecular weight plasticizing compounds to one block of diblock copolymers to form supramolecular comblike blocks leads to hierarchical self-assembly at the block copolymer (long) and amphiphile (short) length scales, in which lamellar-in-lamellar order and the

  15. Change in hydrogen bonding structures of a hydrogel with dehydration

    Science.gov (United States)

    Naohara, Ryo; Narita, Kentaro; Ikeda-Fukazawa, Tomoko

    2017-02-01

    To investigate the mechanisms of structural changes in polymer network and water during dehydration, X-ray diffraction of poly-N,N-dimethylacrylamide (PDMAA) hydrogels was measured. The variation process in the individual structures of water and PDMAA were analyzed by decomposition of the diffraction patterns to separate the respective contributions. The results show that the short-range structures of PDMAA expand during dehydration, whereas the network structure as a whole shrinks. The average length of the hydrogen bonds between water molecules increases with the process. The present results provide a direct evidence of the structural changes of water and polymer in the hydrogel during dehydration.

  16. Exact Results for Quenched Bond Randomness at Criticality

    Science.gov (United States)

    Delfino, Gesualdo

    2017-06-01

    We introduce an exact replica method for the study of critical systems with quenched bond randomness in two dimensions. For the q -state Potts model, we show that a line of renormalization group fixed points interpolates from weak to strong randomness as q -2 grows from small to large values. This theory exhibits a q -independent sector, and allows at the same time for a correlation length exponent which keeps the Ising value and continuously varying magnetization exponent and effective central charge. These findings appear to solve long-standing numerical and theoretical puzzles, and to illustrate the peculiarities which may characterize the conformal field theories of random fixed points.

  17. Cooperativity in Surface Bonding and Hydrogen Bonding of Water and Hydroxyl at Metal Surfaces

    DEFF Research Database (Denmark)

    Schiros, T.; Ogasawara, H.; Naslund, L. A.;

    2010-01-01

    of the mixed phase at metal surfaces. The surface bonding can be considered to be similar to accepting a hydrogen bond, and we can thereby apply general cooperativity rules developed for hydrogen-bonded systems. This provides a simple understanding of why water molecules become more strongly bonded...... to the surface upon hydrogen bonding to OH and why the OH surface bonding is instead weakened through hydrogen bonding to water. We extend the application of this simple model to other observed cooperativity effects for pure water adsorption systems and H3O+ on metal surfaces.......We examine the balance of surface bonding and hydrogen bonding in the mixed OH + H2O overlayer on Pt(111), Cu(111), and Cu(110) via density functional theory calculations. We find that there is a cooperativity effect between surface bonding and hydrogen bonding that underlies the stability...

  18. Anti-Caries Effects of Dental Adhesives Containing Quaternary Ammonium Methacrylates with Different Chain Lengths

    OpenAIRE

    Qi Han; Bolei Li; Xuedong Zhou; Yang Ge; Suping Wang; Mingyun Li; Biao Ren; Haohao Wang; Keke Zhang; Hockin H. K. Xu; Xian Peng; Mingye Feng; Michael D. Weir; Yu Chen; Lei Cheng

    2017-01-01

    The objectives of this study were to investigate the effects of dental adhesives containing quaternary ammonium methacrylates (QAMs) with different alkyl chain lengths (CL) on ecological caries prevention in vitro. Five QAMs were synthesized with a CL = 3, 6, 9, 12, and 16 and incorporated into adhesives. Micro-tensile bond strength and surface charge density were used to measure the physical properties of the adhesives. The proportion change in three-species biofilms consisting of Streptococ...

  19. Modeling single molecule junction mechanics as a probe of interface bonding

    Science.gov (United States)

    Hybertsen, Mark S.

    2017-03-01

    Using the atomic force microscope based break junction approach, applicable to metal point contacts and single molecule junctions, measurements can be repeated thousands of times resulting in rich data sets characterizing the properties of an ensemble of nanoscale junction structures. This paper focuses on the relationship between the measured force extension characteristics including bond rupture and the properties of the interface bonds in the junction. A set of exemplary model junction structures has been analyzed using density functional theory based calculations to simulate the adiabatic potential surface that governs the junction elongation. The junction structures include representative molecules that bond to the electrodes through amine, methylsulfide, and pyridine links. The force extension characteristics are shown to be most effectively analyzed in a scaled form with maximum sustainable force and the distance between the force zero and force maximum as scale factors. Widely used, two parameter models for chemical bond potential energy versus bond length are found to be nearly identical in scaled form. Furthermore, they fit well to the present calculations of N-Au and S-Au donor-acceptor bonds, provided no other degrees of freedom are allowed to relax. Examination of the reduced problem of a single interface, but including relaxation of atoms proximal to the interface bond, shows that a single-bond potential form renormalized by an effective harmonic potential in series fits well to the calculated results. This allows relatively accurate extraction of the interface bond energy. Analysis of full junction models shows cooperative effects that go beyond the mechanical series inclusion of the second bond in the junction, the spectator bond that does not rupture. Calculations for a series of diaminoalkanes as a function of molecule length indicate that the most important cooperative effect is due to the interactions between the dipoles induced by the donor

  20. 23 CFR 658.13 - Length.

    Science.gov (United States)

    2010-04-01

    ... power unit behind the cab and on an over-cab rack. No State shall impose an overall length limitation of... may carry boats on the power unit so long as the length and width restrictions of the vehicles and...) in 23 CFR 658.19. (6) Munitions carriers using dromedary equipment. A truck tractor equipped with...

  1. Length-biased Weighted Maxwell Distribution

    Directory of Open Access Journals (Sweden)

    Kanak Modi

    2015-12-01

    Full Text Available The concept of length-biased distribution can be employed in development of proper models for life-time data. In this paper, we develop the length-biased form of Weighted Maxwell distribution (WMD. We study the statistical properties of the derived distribution including moments, moment generating function, hazard rate, reverse hazard rate, Shannon entropy and estimation of parameters

  2. Segment lengths influence hill walking strategies.

    Science.gov (United States)

    Sheehan, Riley C; Gottschall, Jinger S

    2014-08-22

    Segment lengths are known to influence walking kinematics and muscle activity patterns. During level walking at the same speed, taller individuals take longer, slower strides than shorter individuals. Based on this, we sought to determine if segment lengths also influenced hill walking strategies. We hypothesized that individuals with longer segments would display more joint flexion going uphill and more extension going downhill as well as greater lateral gastrocnemius and vastus lateralis activity in both directions. Twenty young adults of varying heights (below 155 cm to above 188 cm) walked at 1.25 m/s on a level treadmill as well as 6° and 12° up and downhill slopes while we collected kinematic and muscle activity data. Subsequently, we ran linear regressions for each of the variables with height, leg, thigh, and shank length. Despite our population having twice the anthropometric variability, the level and hill walking patterns matched closely with previous studies. While there were significant differences between level and hill walking, there were few hill walking variables that were correlated with segment length. In support of our hypothesis, taller individuals had greater knee and ankle flexion during uphill walking. However, the majority of the correlations were between tibialis anterior and lateral gastrocnemius activities and shank length. Contrary to our hypothesis, relative step length and muscle activity decreased with segment length, specifically shank length. In summary, it appears that individuals with shorter segments require greater propulsion and toe clearance during uphill walking as well as greater braking and stability during downhill walking.

  3. Influence of mandibular length on mouth opening

    NARCIS (Netherlands)

    Dijkstra, PU; Hof, AL; Stegenga, B; De Bont, LGM

    1999-01-01

    Theoretically, mouth opening not only reflects the mobility of the temporomandibular joints (TMJs) but also the mandibular length. Clinically, the exact relationship between mouth opening, mandibular length, and mobility of TMJs is unclear. To study this relationship 91 healthy subjects, 59 women an

  4. Extending electronic length frequency analysis in R

    DEFF Research Database (Denmark)

    Taylor, M. H.; Mildenberger, Tobias K.

    2017-01-01

    Electronic length frequency analysis (ELEFAN) is a system of stock assessment methods using length-frequency (LFQ) data. One step is the estimation of growth from the progression of LFQ modes through time using the von Bertalanffy growth function (VBGF). The option to fit a seasonally oscillating...

  5. Leaf Length Variation in Perennial Forage Grasses

    Directory of Open Access Journals (Sweden)

    Philippe Barre

    2015-08-01

    Full Text Available Leaf length is a key factor in the economic value of different grass species and cultivars in forage production. It is also important for the survival of individual plants within a sward. The objective of this paper is to discuss the basis of within-species variation in leaf length. Selection for leaf length has been highly efficient, with moderate to high narrow sense heritability. Nevertheless, the genetic regulation of leaf length is complex because it involves many genes with small individual effects. This could explain the low stability of QTL found in different studies. Leaf length has a strong response to environmental conditions. However, when significant genotype × environment interactions have been identified, their effects have been smaller than the main effects. Recent modelling-based research suggests that many of the reported environmental effects on leaf length and genotype × environment interactions could be biased. Indeed, it has been shown that leaf length is an emergent property strongly affected by the architectural state of the plant during significant periods prior to leaf emergence. This approach could lead to improved understanding of the factors affecting leaf length, as well as better estimates of the main genetic effects.

  6. Analysis of ureteral length in adult cadavers

    Directory of Open Access Journals (Sweden)

    Hugo F. F. Novaes

    2013-04-01

    Full Text Available Introduction In some occasions, correlations between human structures can help planning surgical intra-abdominal interventions. The previous determination of ureteral length helps pre-operatory planning of surgeries, reduces costs of auxiliary exams, the correct choice of double-J catheter with low morbidity and fewer symptoms, and an adequate adhesion to treatment. Objective To evaluate ureteral length in adult cadavers and to analyze its correlation with anthropometric measures. Materials and Methods: From April 2009 to January 2012 we determined ureteral length of adult cadavers submitted to necropsy and obtained the following measures: height, distance from shoulder to wrist, elbow-wrist, xiphoid appendix-umbilicus, umbilicus-pubis, xiphoid appendix-pubis and between iliac spines. We analyzed the correlations between ureteral length and those anthropometric measures. Results We dissected 115 ureters from 115 adult corpses from April 2009 to January 2012. Median ureteral length didn't vary between sexes or according to height. It was observed no correlation among ureteral length and all considered anthropometric measures in all analyzed subgroups and in general population. There were no significant differences between right and left ureteral measures. Conclusions There is no difference of ureteral length in relation to height or gender (male or female. There is no significant correlation among ureteral length and the considered anthropometric measures.

  7. 7 CFR 29.6024 - Length.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Length. 29.6024 Section 29.6024 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Definitions § 29.6024 Length. The linear measurement of cured tobacco leaves from...

  8. Implicit Hamiltonian formulation of bond graphs

    NARCIS (Netherlands)

    Golo, G.; Schaft, A.J. van der; Breedveld, P.C.; Maschke, B.M.

    2003-01-01

    This paper deals with mathematical formulation of bond graphs. It is proven that the power continuous part of bond graphs, the junction structure, can be associated with a Dirac structure and that equations describing a bond graph model correspond to an implicit port-controlled Hamiltonian system wi

  9. Low temperature anodic bonding to silicon nitride

    DEFF Research Database (Denmark)

    Weichel, Steen; Reus, Roger De; Bouaidat, Salim;

    2000-01-01

    Low-temperature anodic bonding to stoichiometric silicon nitride surfaces has been performed in the temperature range from 3508C to 4008C. It is shown that the bonding is improved considerably if the nitride surfaces are either oxidized or exposed to an oxygen plasma prior to the bonding. Both bulk...

  10. 27 CFR 19.516 - Bond account.

    Science.gov (United States)

    2010-04-01

    ... maximum penal sum, he shall maintain an account of his bond and he shall charge the bond with the amount... return. Where a bond in less than the maximum penal sum has been allocated among two or more plants, as... the penal sum allocated to that plant. (Sec. 201, Pub. L. 85-859, 72 Stat. 1356, as amended (26...

  11. 27 CFR 19.244 - Unit bond.

    Science.gov (United States)

    2010-04-01

    ... sum which represents the penal sum (computed in accordance with § 19.245) for operations at and withdrawals from each plant. If the penal sum of the bond covering a plant, or the penal sum allocated to any... reflected by the penal sum in the bond for such plant. The unit bond shall be conditioned that the...

  12. 27 CFR 19.243 - Withdrawal bond.

    Science.gov (United States)

    2010-04-01

    ... to each plant covered by the bond the part of the total sum which represents the penal sum (computed in accordance with § 19.245) for each such plant. If the penal sum of the bond covering a plant, or the penal sum allocated to any plant (where the bond covers more than one plant), is in an amount...

  13. Halogen Bonding in Hypervalent Iodine Compounds.

    Science.gov (United States)

    Catalano, Luca; Cavallo, Gabriella; Metrangolo, Pierangelo; Resnati, Giuseppe; Terraneo, Giancarlo

    Halogen bonds occur when electrophilic halogens (Lewis acids) attractively interact with donors of electron density (Lewis bases). This term is commonly used for interactions undertaken by monovalent halogen derivatives. The aim of this chapter is to show that the geometric features of the bonding pattern around iodine in its hypervalent derivatives justify the understanding of some of the longer bonds as halogen bonds. We suggest that interactions directionality in ionic and neutral λ(3)-iodane derivatives is evidence that the electron density distribution around iodine atoms is anisotropic, a region of most positive electrostatic potential exists on the extensions of the covalent bonds formed by iodine, and these positive caps affect, or even determine, the crystal packing of these derivatives. For instance, the short cation-anion contacts in ionic λ(3)-iodane and λ(5)-iodane derivatives fully match the halogen bond definition and geometrical prerequisites. The same holds for the short contacts the cation of ionic λ(3)-iodanes forms with lone-pair donors or the short contacts given by neutral λ(3)-iodanes with incoming nucleophiles. The longer and weaker bonds formed by iodine in hypervalent compounds are usually called secondary bondings and we propose that the term halogen bond can also be used. Compared to the term secondary bond, halogen bond may possibly be more descriptive of some bonding features, e.g., its directionality and the relationships between structure of interacting groups and interaction strength.

  14. 25 CFR 214.4 - Bonds.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Bonds. 214.4 Section 214.4 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF OSAGE RESERVATION LANDS, OKLAHOMA, FOR... reserved to change the amount of the bond in any particular case, or to require a new bond in...

  15. Valence-Bond Theory and Chemical Structure.

    Science.gov (United States)

    Klein, Douglas J.; Trinajstic, Nenad

    1990-01-01

    Discussed is the importance of valence bond theory on the quantum-mechanical theory of chemical structure and the nature of the chemical bond. Described briefly are early VB theory, development of VB theory, modern versions, solid-state applications, models, treatment in textbooks, and flaws in criticisms of valence bond theory. (KR)

  16. Hydroxide catalysis bonding of silicon carbide

    NARCIS (Netherlands)

    Veggel, A.A. van; Ende, D.A. van den; Bogenstahl, J.; Rowan, S.; Cunningham, W.; Gubbels, G.H.M.; Nijmeijer, H.

    2008-01-01

    For bonding silicon carbide optics, which require extreme stability, hydroxide catalysis bonding is considered [Rowan, S., Hough, J. and Elliffe, E., Silicon carbide bonding. UK Patent 040 7953.9, 2004. Please contact Mr. D. Whiteford for further information: D.Whiteford@admin.gla.ac.uk]. This techn

  17. Heat Bonding of Irradiated Ethylene Vinyl Acetate

    Science.gov (United States)

    Slack, D. H.

    1986-01-01

    Reliable method now available for joining parts of this difficult-tobond material. Heating fixture encircles ethylene vinyl acetate multiplesocket part, providing heat to it and to tubes inserted in it. Fixtures specially designed to match parts to be bonded. Tube-and-socket bonds made with this technique subjected to tensile tests. Bond strengths of 50 percent that of base material obtained consistently.

  18. 36 CFR 9.48 - Performance bond.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Performance bond. 9.48... MINERALS MANAGEMENT Non-Federal Oil and Gas Rights § 9.48 Performance bond. (a) Prior to approval of a plan of operations, the operator shall be required to file a suitable performance bond with...

  19. 43 CFR 23.9 - Performance bond.

    Science.gov (United States)

    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...

  20. 36 CFR 9.13 - Performance bond.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 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...

  1. 25 CFR 216.8 - Performance bond.

    Science.gov (United States)

    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...

  2. Rebond strength of bonded lingual wire retainers

    NARCIS (Netherlands)

    van Westing, K.; Algera, T.J.; Kleverlaan, C.J.

    2012-01-01

    There is no consensus in the literature concerning the rebonding procedure for orthodontic retainers. The aim of this in vitro study was to evaluate the bond and rebond strength of retainers bonded to enamel surfaces with and without composite remnants. The retainers were bonded with Excite and

  3. Length contraction in Very Special Relativity

    CERN Document Server

    Dutta, Biplab

    2011-01-01

    Glashow and Cohen claim that many results of special theory of relativity (SR) like time dilation, relativistic velocity addition, etc, can be explained by using certain proper subgroups, of the Lorentz group, which collectively form the main body of Very special relativity (VSR). They did not mention about length contraction in VSR. Length contraction in VSR has not been studied at all. In this article we calculate how the length of a moving rod contracts in VSR, particularly in the HOM(2) version. The results are interesting in the sense that in general the length contraction formulas in VSR are different from SR but in many cases the two theories predict similar length contraction of moving rods.

  4. Screening length in dusty plasma crystals

    Science.gov (United States)

    Nikolaev, V. S.; Timofeev, A. V.

    2016-11-01

    Particles interaction and value of the screening length in dusty plasma systems are of great interest in dusty plasma area. Three inter-particle potentials (Debye potential, Gurevich potential and interaction potential in the weakly collisional regime) are used to solve equilibrium equations for two dusty particles suspended in a parabolic trap. The inter-particle distance dependence on screening length, trap parameter and particle charge is obtained. The functional form of inter-particle distance dependence on ion temperature is investigated and compared with experimental data at 200-300 K in order to test used potentials applicability to dusty plasma systems at room temperatures. The preference is given to the Yukawa-type potential including effective values of particle charge and screening length. The estimated effective value of the screening length is 5-15 times larger than the Debye length.

  5. Variable length representation in evolutionary electronics.

    Science.gov (United States)

    Zebulum, R S; Pacheco, M A; Vellasco, M

    2000-01-01

    This work investigates the application of variable length representation (VLR) evolutionary algorithms (EAs) in the field of Evolutionary Electronics. We propose a number of VLR methodologies that can cope with the main issues of variable length evolutionary systems. These issues include the search for efficient ways of sampling a genome space with varying dimensionalities, the task of balancing accuracy and parsimony of the solutions, and the manipulation of non-coding segments. We compare the performance of three proposed VLR approaches to sample the genome space: Increasing Length Genotypes, Oscillating Length Genotypes, and Uniformly Distributed Initial Population strategies. The advantages of reusing genetic material to replace non-coding segments are also emphasized in this work. It is shown, through examples in both analog and digital electronics, that the variable length genotype's representation is natural to this particular domain of application. A brief discussion on biological genome evolution is also provided.

  6. INVESTIGATION OF BONDING IN OXIDE-FIBER (WHISKER) REINFORCED METALS.

    Science.gov (United States)

    CERAMIC FIBERS , BONDING), (*COMPOSITE MATERIALS, BONDING), (*BONDING, CERAMIC FIBERS ), ALUMINUM COMPOUNDS, OXIDES, ZIRCONIUM, NICKEL, TITANIUM, CHROMIUM, SINGLE CRYSTALS, VACUUM, SHEAR STRESSES, SURFACE PROPERTIES, ADDITIVES.

  7. Electron Density Distributions for Millerite, Vaesite , Heazlewoodite and Ni metal: A Case for the Importance of NiNi Bond Paths for Electron Transport

    Science.gov (United States)

    Ross, N. L.; Gibbs, G. V.; Downs, R. T.; Prewitt, C. T.; Rosso, K. M.; Cox, D. F.

    2006-12-01

    Bond paths and the bond critical point properties have been calculated for the bonded interactions comprising the Ni sulfide minerals millerite, vaesite and heazlewoodite and Ni metal. The experimental NiS bond lengths decrease linearly as the magnitudes of the properties each increases in value. Bond paths exist between the Ni atoms in heazlewoodite and millerite for NiNi separations that match the shortest separation in Ni metal, an indicator that the Ni atoms are bonded. Bond paths also exist between the Ni atoms in bulk Ni metal. In addition, the bcp properties of the bonded interactions in Ni metal are virtually the same as those in heazlewoodite and millerite. In contrast, NiNi bond paths are absent in vaesite where the NiNi separations are 60% greater than those in Ni metal. The bcp properties for the NiNi bonded interactions scatter along protractions of the NiS bond length-bcp property trends, suggesting that the two bonded interactions have similar characteristics. NiNi bond paths radiate throughout Ni metal and the metallic heazlewoodite structures as continuous networks whereas the NiNi paths in millerite are restricted to isolated Ni3 rings. Electron transport in Ni metal and heazlewoodite is pictured as occurring along the bond paths, which behave as networks of atomic size wires that radiate in a contiguous circuit throughout the two structures. Unlike heazlewoodite, the electron transport in millerite is pictured as involving a cooperative hopping of the d orbital electrons from the Ni3 rings comprising Ni3S9 clusters to Ni3 rings in adjacent clusters via the p orbitals on the interconnecting S atoms. Vaesite, an insulator at low temperatures and a doped semiconductor at higher temperatures, lacks NiNi bond paths.

  8. Hydrogen bond dynamics in liquid water: Ab initio molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Cheolhee; Kim, Eunae [College of Pharmacy, Chosun University, Gwangju (Korea, Republic of); Yeom, Min Sun [Korea Institute of Science and Technology Information, Daejeon (Korea, Republic of)

    2016-01-15

    The effect of intermolecular interaction on the distribution of the harmonic vibrational frequencies of water molecules was investigated through ab initio molecular dynamics simulations based on the Born-Oppenheimer approach. For single water, the effect of the dynamics of the oxygen atom in single water and the simulation time step on the frequency distribution were examined. The distributions of the OH stretching and HOH bending vibrational frequencies of liquid water were compared to those of single water. The probability distributions of the change in OH bond length and the lifetime of the dangling OH bond were also obtained. The distribution of the frequencies was strongly affected by the long lifetime of the dangling OH bond, resulting in the formation of hydrogen bonds between water molecules.

  9. Microwave Measurements of Maleimide and its Doubly Hydrogen Bonded Dimer with Formic ACID*

    Science.gov (United States)

    Pejlovas, Aaron M.; Kang, Lu; Kukolich, Stephen G.

    2016-06-01

    The microwave spectra were measured for the maleimide monomer and the maleimide-formic acid doubly hydrogen bonded dimer using a pulsed-beam Fourier transform microwave spectrometer. Many previously studied doubly hydrogen bonded dimers are formed between oxygen containing species, so it is important to also characterize and study other dimers containing nitrogen, as hydrogen bonding interactions with nitrogen are found in biological systems such as in DNA. The transition state of the dimer does not exhibit C_2_V symmetry, so the tunneling motion was not expected to be observed based on the symmetry, but it would be very important to also observe the tunneling process for an asymmetric dimer. Single-line b-type transitions were observed, so the tunneling motion was not observed in our microwave spectra. The hydrogen bond lengths were determined using a nonlinear least squares fitting program. *Supported by the NSF CHE-1057796

  10. 19 CFR 125.32 - Merchandise delivered to a bonded store or bonded warehouse.

    Science.gov (United States)

    2010-04-01

    ... warehouse. 125.32 Section 125.32 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND... Merchandise delivered to a bonded store or bonded warehouse. When merchandise is carried, carted or lightered to and received in a bonded store or bonded warehouse, the proprietor or his representative...

  11. Improving orthodontic bonding to silver amalgam.

    Science.gov (United States)

    Zachrisson, B U; Büyükyilmaz, T; Zachrisson, Y O

    1995-01-01

    Flat rectangular tabs (n = 84) prepared from lathe-cut amalgam (ANA 2000) were subjected to aluminum oxide sandblasting or roughening with a diamond bur. Mandibular incisor edgewise brackets were bonded to these tabs using: Concise (Bis-GMA resin); one of three metal-bonding adhesives, viz., Superbond C&B (4-META resin), Panavia Ex (10-MDP Bis-GMA resin) or Geristore (composite base); and Concise after application of the intermediate resins All-Bond 2 Primers A+B, or the Scotch-Bond Multi-Purpose (SBMP) system. All specimens were stored in water at 37 degrees C for 24 hours before tensile bond strength testing. Alignment and uniform loading during testing were secured by engaging a hook in a circular ring soldered onto the bracket slot before bonding. Similar control brackets (n = 12) were bonded with Concise to extracted caries-free mandibular incisors. Bond failure sites were classified by a modified ARI system. Mean tensile bond strengths in the experimental group ranged from 3.4 to 6.4 MPa--significantly weaker than the control sample (13.2 MPa). Bond failure generally occurred at the amalgam/adhesive interface. Superbond C&B created the strongest bonds to amalgam; according to ANOVA and Duncan's Multiple-Range test, they were significantly stronger than the bonds with Panavia Ex and Concise, with Geristore in between. However, the bond strength of Concise to sandblasted amalgam was comparable to the Superbond C&B bonds when coupled with an intermediate application of All-Bond 2 Primers A+B. The SBMP, on the other hand, was less effective.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Kidney Length in Normal Korean Children

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In One; Cheon, Jung Eun [Seoul National University College of Medicine, Seoul (Korea, Republic of); Lee, Young Seok [Dankook University College of Medicine, Cheonan (Korea, Republic of); Lee, Sun Wha [Ewha Womans University College of Medicine, Seoul (Korea, Republic of); Kim, Ok Hwa [Ajou University College of Medicine, Suwon (Korea, Republic of); Kim, Ji Hye [Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Kim, Hong Dae [Kangnam Sacred Heart Hospital, Hanllym University College of Medicine, Seoul (Korea, Republic of); Sim, Jung Suk [Mothers Clinic, Bundang, Seongnam (Korea, Republic of)

    2010-09-15

    Renal length offers important information to detect or follow-up various renal diseases. The purpose of this study was to determine the kidney length of normal Korean children in relation to age, height, weight, body surface area (BSA), and body mass index (BMI). Children between 1 month and 15 years of age without urological abnormality were recruited. Children below 3rd percentile and over 97th percentile for height or weight were excluded. Both renal lengths were measured in the prone position three times and then averaged by experienced radiologists. The mean length and standard deviation for each age group was obtained, and regression equation was calculated between renal length and age, weight, height, BSA, and BMI, respectively. Renal length was measured in 550 children. Renal length grows rapidly until 24 month, while the growth rate is reduced thereafter. The regression equation for age is: renal length (mm) = 45.953 + 1.064 x age (month, {<=} 24 months) (R2 = 0.720) or 62.173 + 0.203 x age (months, > 24 months) (R2 = 0.711). The regression equation for height is: renal length (mm) = 24.494 + 0.457 x height (cm) (R2 = 0.894). The regression equation for weight is: renal length (mm) = 38.342 + 2.117 x weight (kg, {<=}18 kg) (R2 = 0.852) or 64.498 + 0.646 x weight (kg, > 18 kg) (R2 = 0.651). The regression equation for BSA is: renal length (mm) = 31.622 + 61.363 x BSA (m2, {<=} 0.7) (R2 = 0.857) or 52.717 + 29.959 x BSA (m2, > 0.7) (R2 = 0.715). The regression equation for BMI is: renal length (mm) = 44.474 + 1.163 x BMI (R2 = 0.079). This study provides data on the normal renal length and its association with age, weight, height, BSA and BMI. The results of this study will guide the detection and follow-up of renal diseases in Korean children

  13. Effect of ethanol-wet-bonding technique on resin–enamel bonds

    Directory of Open Access Journals (Sweden)

    Muhammet Kerim Ayar

    2014-03-01

    Conclusion: The ethanol-wet-bonding technique may increase the bond strength of commercial adhesives to enamel. The chemical composition of the adhesives can affect the bond strength of adhesives when bonding to acid-etched enamel, using the ethanol-wet-bonding technique. Some adhesive systems used in the present study may simultaneously be applied to enamel and dentin using ethanol-wet-bonding. Furthermore, deploying ethanol-wet-bonding for the tested commercial adhesives to enamel can increase the adhesion abilities of these adhesives to enamel.

  14. Effect of diamond bur cutting efficacy on dentin bond strengths of different bonding systems

    Directory of Open Access Journals (Sweden)

    Shirani F.

    2009-03-01

    Full Text Available "nBackground and Aim: As composite-dentin bond strength is affected by cavity preparation and the bond strength of composite resin to new and used bur prepared dentin has not yet been evaluated, this study evaluated the effects of cutting dentin with different cutting efficacy (new and used of burs on composite-dentin shear bond strength using self-etching primer bonding system and total etching bonding system. "nMaterials and Methods: Sixty caries free human 3rd molar were sectioned in occlosal surface to expose dentin, then polished with silicon carbide paper and randomly divided into four groups. Each group was prepared in a depth of 0.5mm of dentin, using new diamond bur, or used diamond bur. To change into a used bur, each new rough diamond bur had to work on bovine enamel for 30 minutes, under a load of 150g. Then, each group was bonded, using a total etch adhesive (single Bond or a self etch adhesive (clearfil SE Bond So there were 4 groups : 1-SE Bond, New bur; 2-SE Bond , used bur; 3-Single Bond , New bur ; 4-Single Bond, used bur. Similar composite capsules(Filtek Z250 were bonded to dentin surface and cured. specimens were stored in physiologic saline for 48h at 370 c , then put under shearing load to define composite - dentin shear bond strength. Results were interpreted via statistical analysis (T-test & two - way variance. "nResults: Shear bond strength of each group was as follows: 1-(27.3Mpa, 2-(33.5Mpa, 3-(16.9Mpa 4-(19.3Mpa. Statistical analysis proved that shear bond strength of used diamond bur prepared groups (2,4 was more than new diamond bur prepared ones (1,3. This statistical difference, specially, was seen between SE Bond groups (1,2 but not between single Bond groups (3,4. Also, shear bond strength of (SE Bond bonded groups (1,2 were more significantly than (single Bond bonded ones (3,4. "nConclusion: This study show that Bur cutting efficiency influences composite - dentin shear bond strength especially when the

  15. Effects of warm air-drying and spreading on resin bonding.

    Science.gov (United States)

    Galan, D; Williams, P T; Kasloff, Z

    1991-12-01

    The purpose of this study was to compare the effect on resin-to-enamel bonding produced by warm air from a hair dryer, and to correlate changes in resin bond strength with resin tag structure. Herculite-XR resin composite and Bondlite bonding resin were used. The three technique variables were the type of air used for drying, air dryer distance, and drying and spreading time. Control samples were dried and the bonding resin spread with a dental air syringe, whereas warm air from a hair dryer was used on the experimental samples. The bond strength (MPa) was determined in shear at a crosshead speed of 1 mm/min. Following bond strength evaluation, the teeth were immersed in 10% HCl for enamel dissolution and the resin tag structure was examined with the SEM. ANOVA analyses of shear bond strengths were performed. Warm air-drying and spreading for 15 seconds at 6 cm and 5 seconds at 6 cm respectively, produced statistically greater shear bond strengths (x = 20.4 +/- 4.4 MPa, P less than 0.05). The other drying time/distance combinations, including the control (x = 14.4 +/- 3.3 MPa), were not statistically different. Differences in resin tag structure were qualitatively evident under the SEM, with sharp tags produced by the warm air-drying and spreading techniques, compared to the blunt tags created by syringe air-drying and spreading. Warm air-drying and spreading significantly improved the bond strength. No apparent correlation exists between bond strength and tag length.

  16. Simulating increased Lamb wave detection sensitivity of surface bonded fiber Bragg grating

    Science.gov (United States)

    Wee, J.; Hackney, D. A.; Bradford, P. D.; Peters, K. J.

    2017-04-01

    Fiber Bragg grating (FBG) sensors are excellent transducers for collecting ultrasonic wave signals for structural health monitoring (SHM). Typically, FBG sensors are directly bonded to the surface of a structure to detect signals. Unfortunately, demodulating relevant information from the collected signal demands a high signal-to-noise ratio because the structural ultrasonic waves have low amplitudes. Our previous experimental work demonstrated that the optical fiber could be bonded at a distance away from the FBG location, referred to here as remote bonding. This remote bonding technique increased the output signal amplitude compared to the direct bonding case, however the mechanism causing the increase was not explored. In this work, we simulate the previous experimental work through transient analysis based on the finite element method, and the output FBG response is calculated through the transfer matrix method. The model is first constructed without an adhesive to assume an ideal bonding condition, investigating the difference in excitation signal coherence along the FBG length between the two bonding configurations. A second model is constructed with an adhesive to investigate the effect of the presence of the adhesive around the FBG. The results demonstrate that the amplitude increase is originated not from the excitation signal coherence, but from the shear lag effect which causes immature signal amplitude development in the direct bonding case compared to the remote bonding case. The results also indicate that depending on the adhesive properties the surface-bonded optical fiber manifests varying resonant frequency, therefore resulting in a peak amplitude response when the input excitation frequency is matched. This work provides beneficial reference for selecting adhesive and calibrating sensing system for maximum ultrasonic detection sensitivity using the FBG sensor.

  17. Hydrogen bonds in concreto and in computro: the sequel

    Science.gov (United States)

    Stouten, Pieter F. W.; Van Eijck, Bouke P.; Kroon, Jan

    1991-02-01

    In the framework of our comparative research concerning hydrogen bonding in the crystalline and liquid phases we have carried out molecular dynamics (MD) simulations of liquid methanol. Six different rigid three site models are compared. Five of them had been reported in the literature and one (OM2) we developed by a fit to the experimental molar volume, heat of vaporization and neutron weighted radial distribution function. In general the agreement with experiment is satisfactory for the different models. None of the models has an explicit hydrogen bond potential, but five of the six models show a degree of hydrogen bonding comparable to experiments on liquid methanol. The analysis of the simulation hydrogen bonds indicates that there is a distinct preference of the O⋯O axis to lie in the acceptor lone pairs plane, but hardly any for the lone pair directions. Ab initio calculations and crystal structure statistics of OH⋯O hydrogen bonds agree with this observation. The O⋯O hydrogen bond length distributions are similar for most models. The crystal structures show a sharper O⋯O distribution. Explicit introduction of harmonic motion with a quite realistic root mean square amplitude of 0.08 Å to the thermally averaged crystal distribution results in a distribution comparable to OM2 although the maximum of the former is found at shorter distance. On the basis of the analysis of the static properties of all models we conclude that our OM2, Jorgenson's OPLS and Haughney, Ferrario and McDonald's HFM1 models are good candidates for simulations of liquid methanol under isothermal, isochoric conditions. Partly flexible and completely rigid OM2 are simulated at constant pressure and with fixed volume. The flexible simulations give essentially the same (correct) results under both conditions, which is not surprising because the flexible form was fitted under both conditions. Rigid OM2 has a similar potential energy but larger pressure in the

  18. Hydrogen Bonding to Alkanes: Computational Evidence

    DEFF Research Database (Denmark)

    Hammerum, Steen; Olesen, Solveig Gaarn

    2009-01-01

    The structural, vibrational, and energetic properties of adducts of alkanes and strong cationic proton donors were studied with composite ab initio calculations. Hydrogen bonding in [D-H+ H-alkyl] adducts contributes to a significant degree to the interactions between the two components, which...... is substantiated by NBO and AIM results. The hydrogen bonds manifest themselves in the same manner as conventional hydrogen bonds, D-H bond elongation, D-H vibrational stretching frequency red shift and intensity increase, and adduct stabilization. The alkane adducts also exhibit elongation of the C-H bonds...

  19. Valuing Convertible Bonds Based on LSRQM Method

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2014-01-01

    Full Text Available Convertible bonds are one of the essential financial products for corporate finance, while the pricing theory is the key problem to the theoretical research of convertible bonds. This paper demonstrates how to price convertible bonds with call and put provisions using Least-Squares Randomized Quasi-Monte Carlo (LSRQM method. We consider the financial market with stochastic interest rates and credit risk and present a detailed description on calculating steps of convertible bonds value. The empirical results show that the model fits well the market prices of convertible bonds in China’s market and the LSRQM method is effective.

  20. Theoretical study of the intermolecular hydrogen bond interaction for furan-HCl and furan-CHCl3 complexes

    Institute of Scientific and Technical Information of China (English)

    LI; Jiang; (李绛); XIE; Daiqian; (谢代前); YAN; Guosen; (鄢国森)

    2003-01-01

    The nature of the intermolecular hydrogen bond for the furan-HCl and furan-CHCl3 complexes has been studied using ab initio calculations with MP2 level of theory. The new hydrogen bond type of C(Cl)-H...O and C(Cl)-H... interactions are studied also. It is shown that, for the optimized geometries of furan-CHCl3, C-H bond lengths contract and vibrational frequencies are blue-shifted, while for the furan-HCl complex, H-Cl bond lengths elongate and vibrational frequencies are red-shifted. In addition, the NBO analysis indicates that, for the furan-CHCl3 complex, the charge transfers from the lone pair of the proton acceptor to both * (CH) antibonding MO and lone pairs of Cl atom.

  1. Diffusion bonding of copper to niobium

    Science.gov (United States)

    Wagner, Adrian R.

    Processes used to join metal to ceramic at low temperatures have proven to be inefficient because multiple brazing cycles with different brazing temperatures and braze filler metals are required. Even though this is reproducible and robust, it is not ideal due to the manufacturing time and cost associated with multiple brazing cycles. A more efficient and cost effective process is to utilize the diffusion bonding technique to join different metallic layers prior to joining the entire ceramic assembly in one brazing cycle. In this study, the diffusion bonding of copper to niobium was examined. To the author's knowledge, the diffusion bonding of Cu to Nb has not been researched, and the diffusion of Cu into Nb or Nb into Cu has not been observed. A series of diffusion bonding experiments were conducted to determine the optimal bonding time, temperature, and pressure for the Cu-Nb system. The diffusion bonded samples were evaluated using mechanical testing and microscopy. Results from characterization indicate that diffusion of Nb into Cu occurs, and a robust bond with no interfacial voids is formed using different combinations of bonding parameters. The diffusion of Nb into Cu and with failure occurring outside the diffusion bonded region during all mechanical testing indicate that Cu can be bonded to Nb via the diffusion bonding technique.

  2. Infrared spectral evidence and DFT calculations of hydrogen-bonding and molecular structures of acetogenins

    Science.gov (United States)

    Afonso, Sabrina; Silva, Fabiano B.; Silva, Arnaldo F.; Scarminio, Ieda S.; Bruns, Roy E.

    2017-02-01

    FTIR spectra have been measured for 31 different five component - simplex centroid design solvent mixture extracts of shaded and sun-exposed Annonaceous leaves harvested in all four seasons. The spectral frequencies are characteristic of anonnaceous acetogenins known to be a major component of these leaves. Osbnd H stretching spectral bands in the 3100-3600 cm-1 region provide evidence of notable intensity changes for the shaded and sun-exposed leaves. Chemometric principal component analysis involving 264 spectra show that shaded samples tend to have more intense Osbnd H stretching bands than those grown in the sun. B3LYP density functional calculations indicate significant Osbnd H stretching band changes in this region owing to hydrogen bond formation. Weak Osbnd H intensity enhancements, around 40 km mol-1, occur when an Osbnd H group forms a hydrogen bond with the oxygen atom of an adjacent tetrahydrofuran ring oxygen atom. Much more intense enhancements, 400-500 km mol-1, are predicted to occur for acetogenins with two tetrahydrofuran rings for which the Osbnd H group hydrogen bonds with its fartherest removed tetrahydrofuran ring oxygen. Whereas weak or moderate H-bond stretching intensities are obtained for acetogenins with slightly bent carbon chain structures the strongest hydrogen bond intensities are calculated for molecules with a 45° V-type backbone structure. These important structural modifications as well as significant changes in bond lengths and angles owing to hydrogen bonding are detailed.

  3. Bond Strength of Resin Cements to Dentin Using New Universal Bonding Agents

    Science.gov (United States)

    2015-06-30

    indications. The goal of dental adhesives is to provide an equally effective bond to two hard tissues of different nature (Van Meerbeek, 2011). Bonding...tests: An analysis of 50 investigations on bond strength. Quint Int. 1997;28:717–723. Bisco. “All-Bond Universal Light-Cured Dental Adhesive ...Dentsply. “Prime & Bond Elect Universal Dental Adhesive Directions for Use.” Available at: http://www.dentsply.com.au/secure/downloadfile.asp?pid

  4. Liquidity in Government versus Covered Bond Markets

    DEFF Research Database (Denmark)

    Dick-Nielsen, Jens; Gyntelberg, Jacob; Sangill, Thomas

    We present findings on the secondary market liquidity of government and covered bonds in Denmark before, during and after the 2008 financial crisis. The analysis focuses on wholesale trading in the two markets and is based on a complete transaction level dataset covering November 2007 until end...... 2011. Overall, our findings suggest that Danish benchmark covered bonds by and large are as liquid as Danish government bonds - including in periods of market stress. Before the financial crisis of 2008, government bonds were slightly more liquid than covered bonds. During the crisis, trading continued...... in both markets but the government bond market experienced a brief but pronounced decline in market liquidity while liquidity in the covered bond market was more robust - partly reflective of a number of events as well as policy measures introduced in the autumn of 2008. After the crisis, liquidity...

  5. Bonding PMMA microfluidics using commercial microwave ovens

    Science.gov (United States)

    Toossi, A.; Moghadas, H.; Daneshmand, M.; Sameoto, D.

    2015-08-01

    In this paper, a novel low-cost, rapid substrate-bonding technique is successfully applied to polymethyl methacrylate (PMMA) microfluidics bonding for the first time. This technique uses a thin intermediate metallic microwave susceptor layer at the interface of the bonding site (microchannels) which produces localized heating required for bonding during microwave irradiation. The metallic susceptor pattern is designed using a multiphysics simulation model developed in ANSYS Multiphysics software (high-frequency structural simulation (HFSS) coupled with ANSYS-Thermal). In our experiments, the required microwave energy for bonding is delivered using a relatively inexpensive, widely accessible commercial microwave oven. Using this technique, simple PMMA microfluidics prototypes are successfully bonded and sealed in less than 35 seconds with a minimum measured bond strength of 1.375 MPa.

  6. Liquidity in Government versus Covered Bond Markets

    DEFF Research Database (Denmark)

    Dick-Nielsen, Jens; Gyntelberg, Jacob; Sangill, Thomas

    in both markets but the government bond market experienced a brief but pronounced decline in market liquidity while liquidity in the covered bond market was more robust - partly reflective of a number of events as well as policy measures introduced in the autumn of 2008. After the crisis, liquidity......We present findings on the secondary market liquidity of government and covered bonds in Denmark before, during and after the 2008 financial crisis. The analysis focuses on wholesale trading in the two markets and is based on a complete transaction level dataset covering November 2007 until end...... 2011. Overall, our findings suggest that Danish benchmark covered bonds by and large are as liquid as Danish government bonds - including in periods of market stress. Before the financial crisis of 2008, government bonds were slightly more liquid than covered bonds. During the crisis, trading continued...

  7. Inproved grade length limitation of freeways

    Institute of Scientific and Technical Information of China (English)

    XING En-hui; PEI Yu-long

    2006-01-01

    A method of ascertaining grade length limitation of freeways in mountain terrain is presented. The relationship models between 15th percentile speeds and grades were built through the surveys and analyses of operation speeds on 7 typical sections of 3 freeways in mountain terrain. Using 15th percentile and 85th percentile as speed limitations, the methods of determining admitted velocities were put forward according to the grades. Deceleration distances of longitudinal slopeways were analyzed utilizing the theories of vehicle. According to the results of analysis, grade length limitation was loosed. Finally the values of grade length limitation for freeways were put forward. The results could be used as references for freeway design.

  8. Scattering lengths of calcium and barium isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Dammalapati, U.; Willmann, L.; Knoop, S. [Kernfysisch Versneller Instituut (KVI), University of Groningen, Zernikelaan 25, 9747 AA Groningen (Netherlands); LaserLaB Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands)

    2011-11-15

    We have calculated the s-wave scattering length of all the even isotopes of calcium (Ca) and barium (Ba) in order to investigate the prospect of Bose-Einstein condensation (BEC). For Ca we have used an accurate molecular potential based on detailed spectroscopic data. Our calculations show that Ca does not provide other isotopes alternative to the recently Bose condensed {sup 40}Ca that suffers strong losses because of a very large scattering length. For Ba we show by using a model potential that the even isotopes cover a broad range of scattering lengths, opening the possibility of BEC for at least one of the isotopes.

  9. The tree length of an evolving coalescent

    CERN Document Server

    Pfaffelhuber, Peter; Weisshaupt, Heinz

    2009-01-01

    A well-established model for the genealogy of a large population in equilibrium is Kingman's coalescent. For the population together with its genealogy evolving in time, this gives rise to a time-stationary tree-valued process. We study the sum of the branch lengths, briefly denoted as tree length, and prove that the (suitably compensated) sequence of tree length processes converges, as the population size tends to infinity, to a limit process with cadlag paths, infinite infinitesimal variance, and a Gumbel distribution as its equilibrium.

  10. Stylish lengths: Mate choice in flowers

    Indian Academy of Sciences (India)

    B T Ramesha; M D Yetish; G Ravikanth; K N Ganeshaiah; Jaboury Ghazoul; R Uma Shaanker

    2011-06-01

    The styles of flowers may represent an arena for pollen competition in the race to fertilize ovules. Accordingly, selection should favour a longer ‘race’ to better discriminate among variable pollen by increasing style length. Sampling across a taxonomically diverse range of wild and outcrossed species, we found that the distribution of style lengths within plants were skewed towards longer styles, as predicted. In self-pollinated domesticated species, where discrimination among pollen is less important, we found no such pattern. We conclude that style length is under directional selection towards longer styles as a mechanism for mate choice among pollen of variable quality.

  11. Bunch Length Measurements in SPEAR3

    Energy Technology Data Exchange (ETDEWEB)

    Corbett, W.J.; Fisher, A.; Huang, X.; Safranek, J.; Sebek, J.; /SLAC; Lumpkin, A.; /Argonne; Sannibale, F.; /LBL, Berkeley; Mok, W.; /Unlisted

    2007-11-28

    A series of bunch length measurements were made in SPEAR3 for two different machine optics. In the achromatic optics the bunch length increases from the low-current value of 16.6ps rms to about 30ps at 25ma/bunch yielding an inductive impedance of -0.17{Omega}. Reducing the momentum compaction factor by a factor of {approx}60 [1] yields a low-current bunch length of {approx}4ps rms. In this paper we review the experimental setup and results.

  12. Bonds and bands in semiconductors

    CERN Document Server

    Phillips, Jim

    2009-01-01

    This classic work on the basic chemistry and solid state physics of semiconducting materials is now updated and improved with new chapters on crystalline and amorphous semiconductors. Written by two of the world's pioneering materials scientists in the development of semiconductors, this work offers in a single-volume an authoritative treatment for the learning and understanding of what makes perhaps the world's most important engineered materials actually work. Readers will find: --' The essential principles of chemical bonding, electron energy bands and their relationship to conductive and s

  13. Bump bonding of pixel systems

    Energy Technology Data Exchange (ETDEWEB)

    Lozano, M. E-mail: manuel.lozano@cnm.es; Cabruja, E.; Collado, A.; Santander, J.; Ullan, M

    2001-11-01

    A pixel detector consists of an array of radiation sensing elements which is connected to an electronic read-out unit. Many different ways of making this connection between these two different devices are currently being used or considered to be used in the next future. Bonding techniques such as flip chip technology can present real advantages because they allow very fine pitch and a high number of I/Os. This paper presents a review of the different flip chip technologies available and their suitability for manufacturing pixel detectors. The particular problems concerning testing of pixel detectors and thermal issues related to them are pointed out.

  14. Bump bonding of pixel systems

    CERN Document Server

    Lozano, M; Collado, A; Santander, J; Ullán, M

    2001-01-01

    A pixel detector consists of an array of radiation sensing elements which is connected to an electronic read-out unit. Many different ways of making this connection between these two different devices are currently being used or considered to be used in the next future. Bonding techniques such as flip chip technology can present real advantages because they allow very fine pitch and a high number of I/Os. This paper presents a review of the different flip chip technologies available and their suitability for manufacturing pixel detectors. The particular problems concerning testing of pixel detectors and thermal issues related to them are pointed out.

  15. Actor bonds after relationship dissolution

    DEFF Research Database (Denmark)

    Skaates, Maria Anne

    2000-01-01

    Most of the presented papers at the 1st NoRD Workshop can be classified as belonging to the business marketing approach to relationship dissolution. Two papers were conceptual, and the remaining six were empirical studies. The first conceptual study by Skaates (2000) focuses on the nature...... of the actor bonds that remain after a business relationship has ended. The study suggests that an interdisciplinary approach would provide a richer understanding of the phenomenon; this could be achieved by using e.g. Bourdieu's sociological concepts in dissolution research....

  16. Actor bonds after relationship dissolution

    DEFF Research Database (Denmark)

    Skaates, Maria Anne

    2000-01-01

    Most of the presented papers at the 1st NoRD Workshop can be classified as belonging to the business marketing approach to relationship dissolution. Two papers were conceptual, and the remaining six were empirical studies. The first conceptual study by Skaates (2000) focuses on the nature...... of the actor bonds that remain after a business relationship has ended. The study suggests that an interdisciplinary approach would provide a richer understanding of the phenomenon; this could be achieved by using e.g. Bourdieu's sociological concepts in dissolution research....

  17. F-111 Adhesive Bonded Repairs Assessment Program - Progress Report 2: Analysis of FM300-2K Repairs

    Science.gov (United States)

    2015-01-01

    areas of honeycomb- core stiffened aluminium panels, which exist across the fuselage and are used for most control surfaces. The honeycomb panels...typically are manufactured by adhesively bonding an upper and lower aluminium skin to aluminium honeycomb-core. The structure provides added stiffness to... aluminium doubler of similar thickness to the skin thickness is bonded over the exposed core with a prescribed overlap length (Figure 1). The purpose

  18. Atomic volume, atomic distances and chemical bonding in solid metallic elements; Atomvolumen, Atomabstaende und chemische Bindung in festen metallischen Elementen

    Energy Technology Data Exchange (ETDEWEB)

    Troemel, M.; Huebner, S. [Frankfurt Univ. (Germany). Inst. fuer Anorganische Chemie

    2001-05-01

    Relationships between bond lengths and bond numbers and also between atomic volumes and valencies are derived and parameters for their calculation are given for the s-block, p-block, and d-block metals. From the atomic volumes under pressure, the valencies of three solid lanthanoids have been confirmed or redetermined: La 3; Ce 2, 3, and 4; Yb 2 and 3. (orig.)

  19. Structure and bonding in crystalline cesium uranyl tetrachloride under pressure.

    Science.gov (United States)

    Osman, Hussien H; Pertierra, Pilar; Salvadó, Miguel A; Izquierdo-Ruiz, F; Recio, J M

    2016-07-21

    A thorough investigation of pressure effects on the structural properties of crystalline cesium uranyl chloride was performed by means of first-principles calculations within the density functional theory framework. Total energies, equilibrium geometries and vibrational frequencies were computed at selected pressures up to 50 GPa. Zero pressure results present good agreement with available experimental and theoretical data. Our calculated equation of state parameters reveal that Cs2UO2Cl4 is a high compressible material, similar to other ionic compounds with cesium cations, and displays a structural anisotropic behavior guided by the uranyl moiety. An unexpected variation of the U-O bond length, dUO, is detected as pressure is applied. It leads to a dUO-stretching frequency relationship that cannot be described by the traditional Badger's rule. Interestingly enough, it can be explained in terms of a change in the main factor controlling dUO. At low pressure, the charge transferred to the uranyl cation induces an increase of the bond length and a red shift of the stretching frequencies, whereas it is the mechanical effect of the applied pressure above 10 GPa that is the dominant factor that leads to a shortening of dUO and a blue shift of the stretching frequencies.

  20. Quantum Transport in Gated Dangling-Bond Atomic Wires.

    Science.gov (United States)

    Bohloul, S; Shi, Q; Wolkow, Robert A; Guo, Hong

    2017-01-11

    A single line of dangling bonds (DBs) on Si(100)-2 × 1:H surface forms a perfect metallic atomic-wire. In this work, we investigate quantum transport properties of such dangling bond wires (DBWs) by a state-of-the-art first-principles technique. It is found that the conductance of the DBW can be gated by electrostatic potential and orbital overlap due to only a single DB center (DBC) within a distance of ∼16 Å from the DBW. The gating effect is more pronounced for two DBCs and especially, when these two DB "gates" are within ∼3.9 Å from each other. These effective length scales are in excellent agreement with those measured in scanning tunnelling microscope experiments. By analyzing transmission spectrum and density of states of DBC-DBW systems, with or without subsurface doping, for different length of the DBW, distance between DBCs and the DBW, and distance between DB gates, we conclude that charge transport in a DBW can be regulated to have both an on-state and an off-state using only one or two DBs.