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Sample records for bond valence model

  1. Extended Quantum Dimer Model and novel valence-bond phases

    OpenAIRE

    Nakata, Kouki; Totsuka, Keisuke

    2011-01-01

    We extend the quantum dimer model (QDM) introduced by Rokhsar and Kivelson so as to construct a concrete example of the model which exhibits the first-order phase transition between different valence-bond solids suggested recently by Batista and Trugman and look for the possibility of other exotic dimer states. We show that our model contains three exotic valence-bond phases (herringbone, checkerboard and dimer smectic) in the ground-state phase diagram and that it realizes the phase transiti...

  2. Reinterpretation of bond-valence model with bond-order formalism: an improved bond-valence based interatomic potential for PbTiO$_3$

    OpenAIRE

    Liu, Shi; Grinberg, Ilya; Takenaka, Hiroyuki; Rappe, Andrew M.

    2012-01-01

    We present a modified bond-valence model of PbTiO$_3$ based on the principles of bond-valence and bond-valence vector conservation. The relationship between the bond-valence model and the bond-order potential is derived analytically in the framework of a tight-binding model. A new energy term, bond-valence vector energy, is introduced into the atomistic model and the potential parameters are re-optimized. The new model potential can be applied both to canonical ensemble ($NVT$) and isobaric-i...

  3. Extended quantum dimer model and novel valence-bond phases

    International Nuclear Information System (INIS)

    We extend the quantum dimer model (QDM) introduced by Rokhsar and Kivelson so as to construct a concrete example of the model which exhibits the first-order phase transition between different valence-bond solids suggested recently by Batista and Trugman and look for the possibility of other exotic dimer states. We show that our model contains three exotic valence-bond phases (herringbone, checkerboard and dimer smectic) in the ground-state phase diagram and that it realizes the phase transition from the staggered valence-bond solid to the herringbone. The checkerboard phase has four-fold rotational symmetry, while the dimer smectic, in the absence of quantum fluctuations, has massive degeneracy originating from partial ordering only in one of the two spatial directions. A resonance process involving three dimers resolves this massive degeneracy and the dimer smectic becomes ordered (order from disorder)

  4. The itinerant resonating-valence-bond model for superconductivity

    International Nuclear Information System (INIS)

    It has been proposed by Anderson that the pairing interaction in high temperature superconductors La/sub 2-x/ Sr/sub x/ Cuo4 and Yba2Cu3O/sub 7-x/ is magnetic in origin, and the recent discovery of antiferromagnetic ordering in La2CuO4 has been regarded as strong evidence in support of this so-called resonating-valence-bond (RVB) model. Close examination of the ordered state of this material reveals that it is an itinerant antiferromagnet. Accordingly, the superconducting properties must also be studied using the itinerant model approach, rather than the local moment model discussed so far in literature. This paper reports an approximate solution of the itinerant RVB model of superconductivity. It is shown that superconductivity can take place in a narrow region of the parameter space, and that the fluctuating local exchange field causes the superconducting state to be gapless. 19 refs

  5. Coupled valence bond theory

    NARCIS (Netherlands)

    Havenith, R.W.A.

    2005-01-01

    In this Letter, the formulation and implementation of a parallel response property code for non-orthogonal, valence bond wave-functions are described. Test calculations on benzene and cyclobutadiene show that the polarisability and magnetisability tensors obtained using valence bond theory are compa

  6. Distortion of Vz+On coordination polyhedra and parameters of the bond valence model for V-O bonds in inorganic crystals

    International Nuclear Information System (INIS)

    The dependences of average V-O distances in inorganic compounds of vanadium of different valence on the degree of distortion of coordination polyhedra have been obtained by careful statistical treatment of modern structural data banks. Values of bond lengths in undistorted (regular) polyhedra are recommended. Theoretical analysis of the statistical data made it possible to calculate the most likely values of the parameters of the bond valence model: the interatomic distance for the single (two-electron) bond, corresponding to the single valence, and the bond softness parameter. Calculations of the sums of bond valences for some complicated cases (different coordination numbers, mixed vanadium valence) confirmed reliability of the recommended parameters.

  7. Supersymmetric Valence Bond Solid States

    OpenAIRE

    Arovas, Daniel P.; Hasebe, Kazuki; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2009-01-01

    In this work we investigate the supersymmetric version of the valence bond solid (SVBS) state. In one dimension, the SVBS states continuously interpolate between the valence bond states for integer and half-integer spin chains, and they generally describe superconducting valence bond liquid states. Spin and superconducting correlation functions can be computed exactly for these states, and their correlation lengths are equal at the supersymmetric point. In higher dimensions, the wave function...

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

    Directory of Open Access Journals (Sweden)

    S. Adams

    2010-12-01

    Full Text Available 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 or by molecular dynamics (MD simulations. For a wide range of Lithium oxides we could thus model ion transport revealing significant differences to an earlier geometric approach. Our novel BV-based force-field has also been applied to investigate a range of mixed conductors, focusing on cathode materials for lithium ion battery (LIB applications to promote a systematic design of LIB cathodes that combine high energy density with high power density. To demonstrate the versatility of the new BV-based force-field it is applied in exploring various strategies to enhance the power performance of safe low cost LIB materials (LiFePO4, LiVPO4F, LiFeSO4F, etc..

  9. A Valence-Bond Nonequilibrium Solvation Model for a Twisting Cyanine Dye

    CERN Document Server

    McConnell, Sean; Olsen, Seth

    2014-01-01

    We study a two-state valence-bond electronic Hamiltonian model of non-equilibrium solvation during the excited-state twisting reaction of monomethine cyanines. These dyes are of interest because of the strong environment-dependent enhancement of their fluorescence quantum yield that results from suppression of competing non-radiative decay via twisted internal charge-transfer (TICT) states. For monomethine cyanines, where the ground state is a superposition of structures with different bond and charge localization, there are two twisting pathways with different charge localization in the excited state. The Hamiltonian designed to be as simple as possible consistent with a few well-enumerated assumptions. It is defined by three parameters and is a function of two $\\pi$-bond twisting angle coordinates and a single solvation coordinate. For parameters corresponding to symmetric monomethines, there are two low-energy twisting channels on the excited-state surface that lead to a manifold of twisted intramolecular ...

  10. A modified two-state empirical valence bond model for proton transport in aqueous solutions

    International Nuclear Information System (INIS)

    A detailed analysis of the proton solvation structure and transport properties in aqueous solutions is performed using classical molecular dynamics simulations. A refined two-state empirical valence bond (aTS-EVB) method, which is based on the EVB model of Walbran and Kornyshev and the anharmonic water force field, is developed in order to describe efficiently excess proton transport via the Grotthuss mechanism. The new aTS-EVB model clearly satisfies the requirement for simpler and faster calculation, because of the simplicity of the two-state EVB algorithm, while providing a better description of diffusive dynamics of the excess proton and water in comparison with the previous two-state EVB models, which significantly improves agreement with the available experimental data. The results of activation energies for the excess proton and water calculated between 300 and 340 K (the temperature range used in this study) are also found to be in good agreement with the corresponding experimental data

  11. A modified two-state empirical valence bond model for proton transport in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Mabuchi, Takuya, E-mail: mabuchi@nanoint.ifs.tohoku.ac.jp [Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8577 (Japan); Fukushima, Akinori; Tokumasu, Takashi [Institute of Fluid Science, Tohoku University, Sendai, Miyagi 980-8577 (Japan)

    2015-07-07

    A detailed analysis of the proton solvation structure and transport properties in aqueous solutions is performed using classical molecular dynamics simulations. A refined two-state empirical valence bond (aTS-EVB) method, which is based on the EVB model of Walbran and Kornyshev and the anharmonic water force field, is developed in order to describe efficiently excess proton transport via the Grotthuss mechanism. The new aTS-EVB model clearly satisfies the requirement for simpler and faster calculation, because of the simplicity of the two-state EVB algorithm, while providing a better description of diffusive dynamics of the excess proton and water in comparison with the previous two-state EVB models, which significantly improves agreement with the available experimental data. The results of activation energies for the excess proton and water calculated between 300 and 340 K (the temperature range used in this study) are also found to be in good agreement with the corresponding experimental data.

  12. Hiawatha's Valence Bonding

    CERN Document Server

    Laughlin, R B

    2004-01-01

    There is increasing circumstantial evidence that the cuprate superconductors, and correlated-electron materials generally, defy simple materials categorization because of their proximity to one or more continuous zero-temperature phase transitions. This implies that the fifteen-year confusion about the cuprates is not fundamental at all but simply overinterpreted quantum criticality--an effect that seems mysterious by virtue of its hypersensitivity to perturbations, i.e. to sample imperfections in experiment and small modifications of approximation schemes in theoretical modeling, but is really just an unremarkable phase transition of some kind masquerading as something important, a sheep in wolf's clothing. This conclusion is extremely difficult for most physicists even to think about because it requires admitting that an identifiable physical phenomenon might cause the scientific method to fail in some cases. For this reason I have decided to explain the problem in a way that is nonthreatening, easy to read...

  13. Valence-dependent bond-order potentials for modeling Ni-based superalloys

    International Nuclear Information System (INIS)

    The creep properties of Ni-based superalloys degrade with time due to precipitation of topologically close-packed (tcp) phases. We have compiled a structure map of the occurrence of tcp phases for binary transition-metal (TM) compounds from experimental databases. The structure map highlights the well-known role of the average d-band filling for the stability of tcp phases. Atomistic modelling of tcp stability requires extending the second-moment approximation to the electronic density of states (DOS) by including up to at least the sixth moment. We have developed an analytic bond-order potential (BOP) that systematically takes into account higher moment contributions to the DOS and depends explicitly on the valence of the TM elements. By including up to sixth-moment terms the analytic BOP is able to reproduce the structural trend across the non-magnetic 4d and 5d TM series. For the parameterization of the new BOP, we performed extensive density functional theory (DFT) calculations of the elemental and binary compound phases of Ni, the technologically important alloying element Cr, and the refractory metals Mo, Re, and W. In particular, we investigated the tcp phases A15, C14, C15, C36, μ, σ, and χ for the Ni-Cr, Re-W, Mo-Re, and Mo-W binary systems. We discuss the structural trends of the DFT calculations and compare to the predictions of the analytic BOP within the canonical d-band model

  14. A Valence Bond Model for Aqueous Cu(II) and Zn(II) Ions in the AMOEBA Polarizable Force Field

    OpenAIRE

    Xiang, Jin Yu; Ponder, Jay W.

    2012-01-01

    A general molecular mechanics (MM) model for treating aqueous Cu2+ and Zn2+ ions was developed based on valence bond (VB) theory and incorporated into the AMOEBA polarizable force field. Parameters were obtained by fitting molecular mechanics energies to that computed by ab initio methods for gas phase tetra- and hexa-aqua metal complexes. Molecular dynamics (MD) simulations using the proposed AMOEBA-VB model were performed for each transition metal ion in aqueous solution and solvent coordin...

  15. The Valence Bond Interpretation of Molecular Geometry.

    Science.gov (United States)

    Smith, Derek W.

    1980-01-01

    Presents ways in which the valence bond (VB) theory describes the bonding and geometry of molecules, following directly from earlier principles laid down by Pauling and others. Two other theories (molecular orbital approach and valence shell electron pair repulsion) are discussed and compared to VB. (CS)

  16. The variational subspace valence bond method

    Energy Technology Data Exchange (ETDEWEB)

    Fletcher, Graham D. [Argonne National Laboratory, 9700 South Cass Ave., Lemont, Illinois 60439 (United States)

    2015-04-07

    The variational subspace valence bond (VSVB) method based on overlapping orbitals is introduced. VSVB provides variational support against collapse for the optimization of overlapping linear combinations of atomic orbitals (OLCAOs) using modified orbital expansions, without recourse to orthogonalization. OLCAO have the advantage of being naturally localized, chemically intuitive (to individually model bonds and lone pairs, for example), and transferrable between different molecular systems. Such features are exploited to avoid key computational bottlenecks. Since the OLCAO can be doubly occupied, VSVB can access very large problems, and calculations on systems with several hundred atoms are presented.

  17. First order transition between magnetic order and valence-bond order in a 2D frustrated Heisenberg model

    OpenAIRE

    Albrecht, Marc; Mila, Frederic

    1995-01-01

    We study the competition between magnetic order and valence bond order in a two dimensional (2D) frustrated Heisenberg model introduced some time ago by Shastry and Sutherland ({\\sc B. Sriram Shastry} and {\\sc Bill Sutherland}, {\\em Physica} 108{\\bf B},1069 (1981) ) for which a configuration of dimers is known to be the ground state in a certain range of parameters. Using exact diagonalisation of small clusters, linear spin wave theory and Schwinger boson mean field theory, we show that the t...

  18. Multicenter bonds, bond valence and bond charge apportion

    International Nuclear Information System (INIS)

    In the same way that the valence of an atom issues from the definition of bond index, we shoe here that the three-center bond index lends itself to the definition of a bond valence. Within the charge of a bond, we show that its self-charge (i.e., the amount of electron kept by the atoms involved in the bond) is parted in a such a way that the more electronegative atom tends to allot more electronic charge than the other atom. We give examples of these quantities and discuss the results for different kinds of chemical systems. We also show some results for four-center indices and report six-center indices for hexagonal rings. (author). 54 refs., 4 figs., 8 tabs

  19. Valence Bond Glass Phase in the Diluted Kagome Antiferromagnets

    OpenAIRE

    Singh, R. R. P.

    2010-01-01

    We present a theory for site dilution in the Valence Bond Crystal Phase of the Kagome Lattice Heisenberg Model. The presence of an empty site leads to strong singlet bond across the impurity. It also creates a free spin, which delocalizes inside the unit cell. Finite concentration of quenched impurities leads to a Valence Bond Glass phase. This phase has short-range Valence Bond order, no spin-gap, large spin susceptibilities, linear specific heat due to two-level systems, as well as singlet ...

  20. Chemical bonding, elasticity, and valence force field models: a case study for alpha-Pt_2Si and PtSi

    OpenAIRE

    Klepeis, J. E.; Beckstein, O.; Pankratov, O.; Hart, G. L. W.

    2001-01-01

    We have carried out a detailed study of the chemical bonding for two room-temperature stable platinum silicide phases, tetragonal alpha-Pt_2Si and orthorhombic PtSi. An analysis of the valence electronic charge density reveals surprising evidence of covalent three-center bonds in both silicide phases, as well as two-dimensional metallic sheets in alpha-Pt_2Si. These elements of the bonding are further analyzed by constructing valence force field models using the results from recent first prin...

  1. Geometry of trigonal boron coordination sphere in boronic acids derivatives - a bond-valence vector model approach.

    Science.gov (United States)

    Czerwińska, Karolina; Madura, Izabela D; Zachara, Janusz

    2016-04-01

    The systematic analysis of the geometry of three-coordinate boron in boronic acid derivatives with a common [CBO2] skeleton is presented. The study is based on the bond-valence vector (BVV) model [Zachara (2007). Inorg. Chem. 46, 9760-9767], a simple tool for the identification and quantitative estimation of both steric and electronic factors causing deformations of the coordination sphere. The empirical bond-valence (BV) parameters in the exponential equation [Brown & Altermatt (1985). Acta Cryst. B41, 244-247] rij and b, for B-O and B-C bonds were determined using data deposited in the Cambridge Structural Database. The values obtained amount to rBO = 1.364 Å, bBO = 0.37 Å, rBC = 1.569 Å, bBC = 0.28 Å, and they were further used in the calculation of BVV lengths. The values of the resultant BVV were less than 0.10 v.u. for 95% of the set comprising 897 [CBO2] fragments. Analysis of the distribution of BVV components allowed for the description of subtle in- and out-of plane deviations from the `ideal' (sp(2)) geometry of boron coordination sphere. The distortions specific for distinct groups of compounds such as boronic acids, cyclic and acyclic esters, benzoxaboroles and hemiesters were revealed. In cyclic esters the direction of strains was found to be controlled by the ring size effect. It was shown that the syn or anti location of substituents on O atoms is decisive for the deformations direction for both acids and acyclic esters. The greatest strains were observed in the case of benzoxaboroles which showed the highest deviation from the zero value of the resultant BVV. The out-of-plane distortions, described by the vz component of the resultant BVV, were ascertained to be useful in the identification of weak secondary interactions on the fourth coordination site of the boron centre. PMID:27048726

  2. A valence bond model for aqueous Cu(II) and Zn(II) ions in the AMOEBA polarizable force field.

    Science.gov (United States)

    Xiang, Jin Yu; Ponder, Jay W

    2013-04-01

    A general molecular mechanics (MM) model for treating aqueous Cu(2+) and Zn(2+) ions was developed based on valence bond (VB) theory and incorporated into the atomic multipole optimized energetics for biomolecular applications (AMOEBA) polarizable force field. Parameters were obtained by fitting MM energies to that computed by ab initio methods for gas-phase tetra- and hexa-aqua metal complexes. Molecular dynamics (MD) simulations using the proposed AMOEBA-VB model were performed for each transition metal ion in aqueous solution, and solvent coordination was evaluated. Results show that the AMOEBA-VB model generates the correct square-planar geometry for gas-phase tetra-aqua Cu(2+) complex and improves the accuracy of MM model energetics for a number of ligation geometries when compared to quantum mechanical (QM) computations. On the other hand, both AMOEBA and AMOEBA-VB generate results for Zn(2+)-water complexes in good agreement with QM calculations. Analyses of the MD trajectories revealed a six-coordination first solvation shell for both Cu(2+) and Zn(2+) ions in aqueous solution, with ligation geometries falling in the range reported by previous studies. PMID:23212979

  3. The extended variant of the bond valence-bond length correlation curve for boron(III)-oxygen bonds

    International Nuclear Information System (INIS)

    The extended variant of the bond valence (s)-bond length (r) correlation curve for boron(III)-oxygen bonds has been closely approximated using the three-parameter function s = [k/(r - l)] - m, where s is measured in valence units (vu), r is measured in Aa, k = 0.53 Aa.vu, l = 0.975(1) Aa and m = 0.32 vu. The function s = exp[(r0 - r)/b] traditionally used in the modern bond valence model requires the separate set of the bond valence parameters (r0 = 1.362 Aa; b = 0.23 Aa) in order to approximate the above s-r curve for the bonds shorter than ∝1.3 Aa.

  4. The extended variant of the bond valence-bond length correlation curve for boron(III)-oxygen bonds

    Energy Technology Data Exchange (ETDEWEB)

    Sidey, Vasyl [Uzhgorod National Univ. (Ukraine). Dept. of Chemistry and Research Institute for Physics and Chemistry of Solids

    2015-07-01

    The extended variant of the bond valence (s)-bond length (r) correlation curve for boron(III)-oxygen bonds has been closely approximated using the three-parameter function s = [k/(r - l)] - m, where s is measured in valence units (vu), r is measured in Aa, k = 0.53 Aa.vu, l = 0.975(1) Aa and m = 0.32 vu. The function s = exp[(r{sub 0} - r)/b] traditionally used in the modern bond valence model requires the separate set of the bond valence parameters (r{sub 0} = 1.362 Aa; b = 0.23 Aa) in order to approximate the above s-r curve for the bonds shorter than ∝1.3 Aa.

  5. Entanglement in a Valence-Bond-Solid State

    OpenAIRE

    Fan, Heng; Korepin, Vladimir; Roychowdhury, Vwani

    2004-01-01

    We study entanglement in Valence-Bond-Solid state. It describes the ground state of Affleck, Kennedy, Lieb and Tasaki quantum spin chain. The AKLT model has a gap and open boundary conditions. We calculate an entropy of a subsystem (continuous block of spins). It quantifies the entanglement of this block with the rest of the ground state. We prove that the entanglement approaches a constant value exponentially fast as the size of the subsystem increases. Actually we proved that the density ma...

  6. Valence-Bond Concepts in Coordination Chemistry and the Nature of Metal-Metal Bonds.

    Science.gov (United States)

    Pauling, Linus; Herman, Zelek S.

    1984-01-01

    Discusses the valence-bond method, applying it to some coordination compounds of metals, especially those involving metal-metal bonds. Suggests that transition metals can form as many as nine covalent bonds, permitting valence-theory to be extended to transition metal compounds in a more effective way than has been possible before. (JN)

  7. Chemical Bonding: The Orthogonal Valence-Bond View

    Directory of Open Access Journals (Sweden)

    Alexander F. Sax

    2015-04-01

    Full Text Available Chemical bonding is the stabilization of a molecular system by charge- and spin-reorganization processes in chemical reactions. These processes are said to be local, because the number of atoms involved is very small. With multi-configurational self-consistent field (MCSCF wave functions, these processes can be calculated, but the local information is hidden by the delocalized molecular orbitals (MO used to construct the wave functions. The transformation of such wave functions into valence bond (VB wave functions, which are based on localized orbitals, reveals the hidden information; this transformation is called a VB reading of MCSCF wave functions. The two-electron VB wave functions describing the Lewis electron pair that connects two atoms are frequently called covalent or neutral, suggesting that these wave functions describe an electronic situation where two electrons are never located at the same atom; such electronic situations and the wave functions describing them are called ionic. When the distance between two atoms decreases, however, every covalent VB wave function composed of non-orthogonal atomic orbitals changes its character from neutral to ionic. However, this change in the character of conventional VB wave functions is hidden by its mathematical form. Orthogonal VB wave functions composed of orthonormalized orbitals never change their character. When localized fragment orbitals are used instead of atomic orbitals, one can decide which local information is revealed and which remains hidden. In this paper, we analyze four chemical reactions by transforming the MCSCF wave functions into orthogonal VB wave functions; we show how the reactions are influenced by changing the atoms involved or by changing their local symmetry. Using orthogonal instead of non-orthogonal orbitals is not just a technical issue; it also changes the interpretation, revealing the properties of wave functions that remain otherwise undetected.

  8. Novel Order Parameter to Characterize Valence-Bond-Solid States

    OpenAIRE

    Nakamura, Masaaki; Todo, Synge

    2002-01-01

    We propose an order parameter to characterize valence-bond-solid (VBS) states in quantum spin chains, given by the ground-state expectation value of a unitary operator appearing in the Lieb-Schultz-Mattis argument. We show that the order parameter changes the sign according to the configuration of the valence bonds. This allows us to determine the phase transition point in between different VBS states accurately. We demonstrate this theory in the bond-alternating Heisenberg chain and in the f...

  9. Exploring covalently bonded diamondoid particles with valence photoelectron spectroscopy

    CERN Document Server

    Zimmermann, Tobias; Knecht, Andre; Fokin, Andrey A; Koso, Tetyana V; Chernish, Lesya V; Gunchenko, Pavel A; Schreiner, Peter R; Möller, Thomas; Rander, Torbjörn

    2013-01-01

    We investigated the electronic structures of diamondoid particles in the gas phase, utilizing valence photoelectron spectroscopy. The samples were singly or doubly covalently bonded dimers or trimers of the lower diamondoids. Both bond type and the combination of the bonding partners affect the overall electronic structures. For singly bonded particles we observe a small impact of the bond type on the electronic structure, whereas for doubly bonded particles the connecting bond is the deciding factor, determining the electronic structure of the uppermost occupied orbitals. In the singly bonded particles a superposition of the bonding partner orbitals determines the overall electronic structure. The strength of quantum confinement effects, i.e., the localization of electrons, depends on the bonding partner orbital energy difference. The experimental findings correspond well to density functional theory computations.

  10. Topological Structure of Phase Vortex in Resonating Valence Bond Superconductivity

    Institute of Scientific and Technical Information of China (English)

    SHI Xu-Guang; DUAN Yi-Shi

    2006-01-01

    In this paper, based on the Schrodinger equation and the ψ-mapping theory, the accurate expression for the gradient of resonating valence bond superconducting phase Θs is found. The expression of (△→)Θs is just the velocity flow (V) without considering the coefficient. The curl of (△→)Θs is where the vortex lies, and has important relation to δ2(ψ) and an important relation to the zero points of resonating valence bond superconducting order parameter ψ. The topological structure of the vortex is characterized by the ψ-mapping topological numbers Hopf-index and Brouwer degrees. The Ginzberg-Landau equation in resonating valence bond state also is discussed in this theory. The magnetic property is discussed also.

  11. Resonating Valence Bond states for low dimensional S=1 antiferromagnets

    Science.gov (United States)

    Liu, Zheng-Xin; Zhou, Yi; Ng, Tai-Kai

    2014-03-01

    We study S = 1 spin liquid states in low dimensions. We show that the resonating-valence-bond (RVB) picture of S = 1 / 2 spin liquid state can be generalized to S = 1 case. For S = 1 system, a many-body singlet (with even site number) can be decomposed into superposition of products of two-body singlets. In other words, the product states of two-body singlets, called the singlet pair states (SPSs), are over complete to span the Hilbert space of many-body singlets. Furthermore, we generalized fermionic representation and the corresponding mean field theory and Gutzwiller projected stats to S = 1 models. We applied our theory to study 1D anti-ferromagnetic bilinear-biquadratic model and show that both the ground states (including the phase transition point) and the excited states can be understood excellently well within the framework. Our method can be applied to 2D S = 1 antiferromagnets.

  12. Regional versus Global Entanglement in Resonating-Valence-Bond states

    CERN Document Server

    Chandran, A; Sen, A; Sen, U; Vedral, V; Chandran, Anushya; Kaszlikowski, Dagomir; Sen, Aditi; Sen, Ujjwal; Vedral, Vlatko

    2007-01-01

    We investigate the entanglement properties of resonating valence bond states on two and higher dimensional lattices, which play an important role in the theory of conductivity. We show that these states are genuinely multipartite entangled, while there is only a negligible amount of two-site entanglement. We comment on possible physical implications of our findings.

  13. Using the constrained DFT approach in generating diabatic surfaces and off diagonal empirical valence bond terms for modeling reactions in condensed phases.

    Science.gov (United States)

    Hong, Gongyi; Rosta, Edina; Warshel, Arieh

    2006-10-01

    The empirical valence bond (EVB) model provides an extremely powerful way for modeling and analyzing chemical reactions in solutions and proteins. However, this model is based on the unverified assumption that the off diagonal elements of the EVB Hamiltonian do not change significantly upon transfer of the reacting system from one phase to another. This ad hoc assumption has been rationalized by its consistency with empirically observed linear free energy relationships, as well as by other qualitative considerations. Nevertheless, this assumption has not been rigorously established. The present work explores the validity of the above EVB key assumption by a rigorous numerical approach. This is done by exploiting the ability of the frozen density functional theory (FDFT) and the constrained density functional theory (CDFT) models to generate convenient diabatic states for QM/MM treatments, and thus to examine the relationship between the diabatic and adiabatic surfaces, as well as the corresponding effective off diagonal elements. It is found that, at least for the test case of S(N)()2 reactions, the off diagonal element does not change significantly upon moving from the gas phase to solutions and thus the EVB assumption is valid and extremely useful. PMID:17004821

  14. Bond charge approximation for valence electron density in elemental semiconductors

    International Nuclear Information System (INIS)

    The spatial valence electron distribution in silicon and diamond is calculated in adiabatic bond charge approximation at zero temperature when bond charges have the Gaussian shape and their tensor character is taken into account. An agreement between theory and experiment has been achieved. For this purpose Xia's ionic pseudopotentials and Schulze-Unger's dielectric function are used. By two additional parameters Asub(B) and Zsub(B)sup(') we describe the spatial extent of the bond charge and local-field corrections, respectively. The parameter Zsub(B)sup(') accounts for the ratio between the Coulomb and exchange correlation interactions of the valence electrons and its silicon and diamond values have different signs. (author)

  15. The application of cholesky decomposition in valence bond calculation.

    Science.gov (United States)

    Gong, Xiping; Chen, Zhenhua; Wu, Wei

    2016-09-01

    The Cholesky decomposition (CD) technique, used to approximate the two-electron repulsion integrals (ERIs), is applied to the valence bond self-consistent field (VBSCF) method. Test calculations on ethylene, C2 n H2 n +2 , and C2 n H4 n -2 molecules (n = 1-7) show that the performance of the VBSCF method is much improved using the CD technique, and thus, the integral transformation from basis functions to VB orbitals is no longer the bottleneck in VBSCF calculations. The errors of the CD-based ERIs and of the total energy are controlled by the CD threshold, for which a value of 10(-6) ensures to control the total energy error within 10(-6) Hartree. © 2016 Wiley Periodicals, Inc. PMID:27377531

  16. Conceptual chemistry approach towards the support effect in supported vanadium oxides : Valence bond calculations on the ionicity of vanadium catalysts

    NARCIS (Netherlands)

    Fievez, Tim; De Proft, Frank; Geerlings, Paul; Weckhuysen, Bert M.; Havenith, Remco W. A.

    2011-01-01

    The concept of bond ionicity, obtained via a valence bond analysis, is invoked in the interpretation of the catalytic activity of supported vanadium oxides, in analogy with previous work conducted within the framework of conceptual DFT. For a set of model clusters representing the vanadium oxide sup

  17. Valence-bond stripes in cuprates: ARPES and inter-layer tunneling

    Energy Technology Data Exchange (ETDEWEB)

    Wollny, Alexander; Vojta, Matthias [Institut fuer Theoretische Physik, Universitaet zu Koeln (Germany)

    2009-07-01

    The effect of stripe formation in the underdoped cuprates has been a much discussed topic for more than ten years. Motivated by recent neutron scattering and STM experiments we develop a phenomenological mean-field model for valence-bond stripes dominated by local singlet formation. We explore the electronic spectrum for valence-bond stripes and its interplay with d-wave superconductivity. The results are compatible with ARPES data for La{sub 1.675}Eu{sub 0.2}Sr{sub 0.125}CuO{sub 4}. Further we derive the effect of long ranged stripe order (with and without magnetic ordering) on the interlayer tunneling between two CuO{sub 2}-layers, giving an alternative mechanism, besides the anti-phase SC scenario, for effective layer decoupling in La{sub 1.875}Ba{sub 0.125}CuO{sub 4}.

  18. Valence-bond stripes in cuprates: ARPES and inter-layer tunneling

    International Nuclear Information System (INIS)

    The effect of stripe formation in the underdoped cuprates has been a much discussed topic for more than ten years. Motivated by recent neutron scattering and STM experiments we develop a phenomenological mean-field model for valence-bond stripes dominated by local singlet formation. We explore the electronic spectrum for valence-bond stripes and its interplay with d-wave superconductivity. The results are compatible with ARPES data for La1.675Eu0.2Sr0.125CuO4. Further we derive the effect of long ranged stripe order (with and without magnetic ordering) on the interlayer tunneling between two CuO2-layers, giving an alternative mechanism, besides the anti-phase SC scenario, for effective layer decoupling in La1.875Ba0.125CuO4.

  19. Modern ab initio valence bond theory calculations reveal charge shift bonding in protic ionic liquids.

    Science.gov (United States)

    Patil, Amol Baliram; Bhanage, Bhalchandra Mahadeo

    2016-06-21

    The nature of bonding interactions between the cation and the anion of an ionic liquid is at the heart of understanding ionic liquid properties. A particularly interesting case is a special class of ionic liquids known as protic ionic liquids. The extent of proton transfer in protic ionic liquids has been observed to vary according to the interacting species. Back proton transfer renders protic ionic liquids volatile and to be considered as inferior ionic liquids. We try to address this issue by employing modern ab initio valence bond theory calculations. The results indicate that the bonding in the cation and the anion of a prototypical ionic liquid, ethylammonium nitrate, is fundamentally different. It is neither characteristic of covalent/polar covalent bonding nor ionic bonding but rather charge shift bonding as a resonance hybrid of two competing ionic molecular electronic structure configurations. An investigation of other analogous protic ionic liquids reveals that this charge shift bonding seems to be a typical characteristic of protic ionic liquids while the ionic solid analogue compound ammonium nitrate has less charge shift bonding character as compared to protic ionic liquids. Further the extent of charge shift bonding character has been found to be congruent with the trends in many physicochemical properties such as melting point, conductivity, viscosity, and ionicity of the studied ionic liquids indicating that percentage charge shift character may serve as a key descriptor for large scale computational screening of ionic liquids with desired properties. PMID:27229870

  20. Red-Shifting versus Blue-Shifting Hydrogen Bonds: Perspective from Ab Initio Valence Bond Theory.

    Science.gov (United States)

    Chang, Xin; Zhang, Yang; Weng, Xinzhen; Su, Peifeng; Wu, Wei; Mo, Yirong

    2016-05-01

    Both proper, red-shifting and improper, blue-shifting hydrogen bonds have been well-recognized with enormous experimental and computational studies. The current consensus is that there is no difference in nature between these two kinds of hydrogen bonds, where the electrostatic interaction dominates. Since most if not all the computational studies are based on molecular orbital theory, it would be interesting to gain insight into the hydrogen bonds with modern valence bond (VB) theory. In this work, we performed ab initio VBSCF computations on a series of hydrogen-bonding systems, where the sole hydrogen bond donor CF3H interacts with ten hydrogen bond acceptors Y (═NH2CH3, NH3, NH2Cl, OH(-), H2O, CH3OH, (CH3)2O, F(-), HF, or CH3F). This series includes four red-shifting and six blue-shifting hydrogen bonds. Consistent with existing findings in literature, VB-based energy decomposition analyses show that electrostatic interaction plays the dominating role and polarization plays the secondary role in all these hydrogen-bonding systems, and the charge transfer interaction, which denotes the hyperconjugation effect, contributes only slightly to the total interaction energy. As VB theory describes any real chemical bond in terms of pure covalent and ionic structures, our fragment interaction analysis reveals that with the approaching of a hydrogen bond acceptor Y, the covalent state of the F3C-H bond tends to blue-shift, due to the strong repulsion between the hydrogen atom and Y. In contrast, the ionic state F3C(-) H(+) leads to the red-shifting of the C-H vibrational frequency, owing to the attraction between the proton and Y. Thus, the relative weights of the covalent and ionic structures essentially determine the direction of frequency change. Indeed, we find the correlation between the structural weights and vibrational frequency changes. PMID:27074500

  1. Resonant valence bond states in zinc vacancies induce the ferromagnetism of ZnO

    Science.gov (United States)

    Sun, Shih-Jye

    2016-05-01

    A theoretical model was proposed to investigate the mechanism of ferromagnetism in ZnO as well as to simulate the experimental result that the ferromagnetism can be enhanced by UV irradiation as UV photon energy is equivalent to the band gap. In the model, the spin moments arise from the trapped electrons in oxygen vacancy states and coexist with the itinerant electrons which reside in zinc vacancy states and fall into resonant valence bond states. Charge exchange between the conduction band of ZnO and both vacancy states makes electrons on both vacancy states delocalized and results in a decrease of the ferromagnetism as well.

  2. Chemical Bonding in Solids. On the Generalization of the Concept of Bond Order and Valence for Infinite Periodical Structures

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert

    2005-01-01

    Roč. 114, 1-3 (2005), s. 208-212. ISSN 1432-881X R&D Projects: GA AV ČR(CZ) IAA4072403 Institutional research plan: CEZ:AV0Z4072921 Keywords : bonding in solids * bond order * valence Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.179, year: 2005

  3. Advances in Generalized Valence Bond-Coupled Cluster Methods for Electronic Structure Theory

    OpenAIRE

    Lawler, Keith Vanoy

    2009-01-01

    The electron-electron correlation term in the electronic energy of a molecule is the most difficult term to compute, yet it is of both qualitative and quantitative importance for a diverse range of chemical applications of computational quantum chemistry. Generalized Valence Bond-Coupled Cluster (GVB-CC) methods are computationally efficient, size-consistent wavefunction based methods to capture the most important static (valence) contributions to the correlation energy. Despite these advanta...

  4. Valence Bond Solid Order Near Impurities in Two-Dimensional Quantum Antiferromagnets

    OpenAIRE

    Metlitski, Max A.; Sachdev, Subir

    2008-01-01

    Recent scanning tunneling microscopy (STM) experiments on underdoped cuprates have displayed modulations in the local electronic density of states, which are centered on a Cu-O-Cu bond [Kohsaka et al. Science 315 1380 (2007)]. As a paradigm of the pinning of such bond-centered ordering in strongly correlated systems, we present the theory of valence bond solid (VBS) correlations near a single impurity in a square lattice antiferromagnet. The antiferromagnet is assumed to be in the vicinity of...

  5. The new Resonating Valence Bond Method for ab-initio Electronic Simulations

    CERN Document Server

    Sorella, Sandro

    2013-01-01

    The Resonating Valence Bond theory of the chemical bond was introduced soon after the discovery of quantum mechanics and has contributed to explain the role of electron correlation within a particularly simple and intuitive approach where the chemical bond between two nearby atoms is described by one or more singlet electron pairs. In this chapter Pauling's resonating valence bond theory of the chemical bond is revisited within a new formulation, introduced by P.W. Anderson after the discovery of High-Tc superconductivity. It is shown that this intuitive picture of electron correlation becomes now practical and efficient, since it allows us to faithfully exploit the locality of the electron correlation, and to describe several new phases of matter, such as Mott insulators, High-Tc superconductors, and spin liquid phases.

  6. Maximized string order parameters in the valence bond solid states of quantum integer spin chains

    OpenAIRE

    Tu, Hong-Hao; Zhang, Guang-Ming; Xiang, Tao

    2008-01-01

    We propose a set of maximized string order parameters to describe the hidden topological order in the valence bond solid states of quantum integer spin-S chains. These optimized string order parameters involve spin-twist angles corresponding to $Z_{S+1}$ rotations around $z$ or $x$-axes, suggesting a hidden $Z_{S+1}\\times Z_{S+1}$ symmetry. Our results also suggest that a local triplet excitation in the valence bond solid states carries a $Z_{S+1}$ topological charge measured by these maximiz...

  7. On the valence model for radiative capture

    International Nuclear Information System (INIS)

    We give several parametrizations for the elastic scattering and radiative capture cross sections for low neutron bombarding energy and discuss the relationship between the corresponding resonance parameters. We then peform an extensive investigation of the valence radiative capture model of Lane and Lynn. This model is formulated here in the frame of the shell-model approach. We exhibit the similarities and differences between our results and those derived from the R-matrix approach by Lane and Lynn on the one hand and from the optical-model approach by Lane and Mughabghab on the other hand. Particular attention is paid to the choice of the average potential well in the shell model approach, in relation to the proper way to identify theoretical quantities and phenomenological parameters. We show that practically equivalent results can be obtained from a complex average potential well and from a suitably chosen real potential well. The following topics are investigated formally and numerically: dependence of the various theoretical expressions on the choice of the (real or complex) average potential well; relative importance of external and internal capture; dependence of photon widths and background cross section on mass number (for thermal energy and for E=100 keV); dependence of the resonance parameters and background cross sections on energy, for A=60; comparison between experimental data and theoretical values for radiative capture on 56Fe and 60Ni. We discuss the conditions of validity of the valence capture model The contribution of the low-lying excited target states is investigated formally and numerically

  8. Effects of Magnetic Field on the Valence Bond Property of the Double-Quantum-Dot Molecule

    Institute of Scientific and Technical Information of China (English)

    王立民; 罗莹; 马本堃

    2002-01-01

    The effects of the magnetic field on the valence bond property of the double-quantum-dot molecule are numerically studied by the finite element method and perturbation approach because of the absence of cylindrical symmetry in the horizontally coupled dots. The calculation results show that the energy value of the ground state changes differently from that of the first excited state with increasing magnetic field strength, and they cross under a certain magnetic field. The increasing magnetic field makes the covalent bond state change into an ionic bond state, which agrees qualitatively with experimental results and makes ionic bond states remain. The oscillator strength of transition between covalent bond states decreases distinctly with the increasing magnetic field strength, when the molecule is irradiated by polarized light. Such a phenomenon is possibly useful for actual applications.

  9. Plaquette Valence Bond Theory of High-Temperature Superconductivity

    OpenAIRE

    Harland, M; Katsnelson, M I; Lichtenstein, A.I.

    2016-01-01

    We present a strong-coupling approach to the theory of high-temperature superconductivity based on the observation of a quantum critical point in the plaquette within the t,t' Hubbard model. The crossing of ground state energies in the N=2,3,4 sectors occurs for parameters close to the optimal doping. The theory predicts the maximum of the d(x2-y2)-wave order parameter at the border between localized and itinerant electron behavior and gives a natural explanation for the pseudo-gap formation ...

  10. Application and development of quantum chemical methods. Density functional theory and valence bond theory

    OpenAIRE

    Ying, Fuming

    2010-01-01

    This thesis deals with two disjoint subdiciplines of quantum chemistry.  One isthe most used electronic structure method today, density functional theory(DFT), and the other one of the least used electronic structure methods,valence bond theory (VB).  The work on DFT is based on previous developments inthe department in density functional response theory and involves studies ofhyperfine coupling constants which are measured in electron paramagneticresonance experiments.  The method employed i...

  11. Resonating-Valence-Bond Physics Is Not Always Governed by the Shortest Tunneling Loops

    Science.gov (United States)

    Ralko, Arnaud; Rousochatzakis, Ioannis

    2015-10-01

    It is well known that the low-energy sector of quantum spin liquids and other magnetically disordered systems is governed by short-ranged resonating-valence bonds. Here we show that the standard minimal truncation to the nearest-neighbor valence-bond basis fails completely even for systems where it should work the most, according to received wisdom. This paradigm shift is demonstrated for the quantum spin-1 /2 square kagome, where strong geometric frustration, similar to the kagome, prevents magnetic ordering down to zero temperature. The shortest tunneling events bear the strongest longer-range singlet fluctuations, leading to amplitudes that do not drop exponentially with the length of the loop L , and to an unexpected loop-six valence-bond crystal, which is otherwise very high in energy at the minimal truncation level. The low-energy effective description gives in addition a clear example of correlated loop processes that depend not only on the type of the loop but also on its lattice embedding, a direct manifestation of the long-range nature of the virtual singlets.

  12. On the Relative Merits of Non-Orthogonal and Orthogonal Valence Bond Methods Illustrated on the Hydrogen Molecule

    Science.gov (United States)

    Angeli, Celestino; Cimiraglia, Renzo; Malrieu, Jean-Paul

    2008-01-01

    Valence bond (VB) is one of the cornerstone theories of quantum chemistry. Even if in practical applications the molecular orbital (MO) approach has obtained more attention, some basic chemical concepts (such as the nature of the chemical bond and the failure of the single determinant-based MO methods in describing the bond cleavage) are normally…

  13. The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene

    Energy Technology Data Exchange (ETDEWEB)

    Domin, D.; Braida, Benoit; Lester Jr., William A.

    2008-05-30

    This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).

  14. Valence XPS structure and chemical bond in Cs2UO2Cl4

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2016-01-01

    Full Text Available Quantitative analysis was done of the valence electrons X-ray photoelectron spectra structure in the binding energy (BE range of 0 eV to ~35 eV for crystalline dicaesium tetrachloro-dioxouranium (VI (Cs2UO2Cl4. This compound contains the uranyl group UO2. The BE and structure of the core electronic shells (~35 eV-1250 eV, as well as the relativistic discrete variation calculation results for the UO2Cl4(D4h cluster reflecting U close environment in Cs2UO2Cl4 were taken into account. The experimental data show that many-body effects due to the presence of cesium and chlorine contribute to the outer valence (0-~15 eV BE spectral structure much less than to the inner valence (~15 eV-~35 eV BE one. The filled U5f electronic states were theoretically calculated and experimentally confirmed to be present in the valence band of Cs2UO2Cl4. It corroborates the suggestion on the direct participation of the U5f electrons in the chemical bond. Electrons of the U6p atomic orbitals participate in formation of both the inner (IVMO and the outer (OVMO valence molecular orbitals (bands. The filled U6p and the O2s, Cl3s electronic shells were found to make the largest contributions to the IVMO formation. The molecular orbitals composition and the sequence order in the binding energy range 0 eV-~35 eV in the UO2Cl4 cluster were established. The experimental and theoretical data allowed a quantitative molecular orbitals scheme for the UO2Cl4 cluster in the BE range 0-~35 eV, which is fundamental for both understanding the chemical bond nature in Cs2UO2Cl4 and the interpretation of other X-ray spectra of Cs2UO2Cl4. The contributions to the chemical binding for the UO2Cl4 cluster were evaluated to be: the OVMO contribution - 76%, and the IVMO contribution - 24 %.

  15. Nonorthogonal orbital based N-body reduced density matrices and their applications to valence bond theory. I. Hamiltonian matrix elements between internally contracted excited valence bond wave functions

    Science.gov (United States)

    Chen, Zhenhua; Chen, Xun; Wu, Wei

    2013-04-01

    In this series, the n-body reduced density matrix (n-RDM) approach for nonorthogonal orbitals and their applications to ab initio valence bond (VB) methods are presented. As the first paper of this series, Hamiltonian matrix elements between internally contracted VB wave functions are explicitly provided by means of nonorthogonal orbital based RDM approach. To this end, a more generalized Wick's theorem, called enhanced Wick's theorem, is presented both in arithmetical and in graphical forms, by which the deduction of expressions for the matrix elements between internally contracted VB wave functions is dramatically simplified, and the matrix elements are finally expressed in terms of tensor contractions of electronic integrals and n-RDMs of the reference VB self-consistent field wave function. A string-based algorithm is developed for the purpose of evaluating n-RDMs in an efficient way. Using the techniques presented in this paper, one is able to develop new methods and efficient algorithms for nonorthogonal orbital based many-electron theory much easier than by use of the first quantized formulism.

  16. Application of bond valence method in the non-isovalent semiconductor alloy (GaN)$_{1-x}$(ZnO)$_x$

    OpenAIRE

    Liu, Jian

    2015-01-01

    This paper studies the bond valence method (BVM) and its application in the non-isovalent semiconductor alloy (GaN)$_{\\rm{1-x}}$(ZnO)$_{\\rm{x}}$. Particular attention is paid to the role of short-range order (SRO). A physical interpretation based on atomic orbital interaction is proposed and examined by density-functional theory (DFT) calculations. Combining BVM with Monte-Carlo simulations and a DFT-based cluster expansion model, bond-length distributions and bond-angle variations are predic...

  17. Resonating Valence Bond Quantum Monte Carlo: Application to the ozone molecule

    CERN Document Server

    Azadi, Sam; Kühne, Thomas D

    2015-01-01

    We study the potential energy surface of the ozone molecule by means of Quantum Monte Carlo simulations based on the resonating valence bond concept. The trial wave function consists of an antisymmetrized geminal power arranged in a single-determinant that is multiplied by a Jastrow correlation factor. Whereas the determinantal part incorporates static correlation effects, the augmented real-space correlation factor accounts for the dynamics electron correlation. The accuracy of this approach is demonstrated by computing the potential energy surface for the ozone molecule in three vibrational states: symmetric, asymmetric and scissoring. We find that the employed wave function provides a detailed description of rather strongly-correlated multi-reference systems, which is in quantitative agreement with experiment.

  18. Some considerations about bond indices in non-orthogonal bases and the MO calculation of valence and oxidation number

    International Nuclear Information System (INIS)

    In order to guarantee the desired invariance properties of bond indices, the importance of expliciting the tensor character of the matrices concerned, so as to deal with a contraction in the tensor sense between a covariant index and a contravariant one is shown. An MO valence definition using Wiberg's indices is generalized to non-orthogonal bases and a straightforward definition of oxidation numbers is proposed. IEH calculations of their magnitudes for some appropriate examples are performed: they emphasize the role of 'secondary' bonds in N and C-containing compounds; the hydrogen behaviour in half-bonds and strong H-bonds is satisfactorily accounted for; valence and oxidation number values are assigned to Fe, Co and Ni in a few complexes. (Author)

  19. Block correlated second order perturbation theory with a generalized valence bond reference function

    International Nuclear Information System (INIS)

    The block correlated second-order perturbation theory with a generalized valence bond (GVB) reference (GVB-BCPT2) is proposed. In this approach, each geminal in the GVB reference is considered as a “multi-orbital” block (a subset of spin orbitals), and each occupied or virtual spin orbital is also taken as a single block. The zeroth-order Hamiltonian is set to be the summation of the individual Hamiltonians of all blocks (with explicit two-electron operators within each geminal) so that the GVB reference function and all excited configuration functions are its eigenfunctions. The GVB-BCPT2 energy can be directly obtained without iteration, just like the second order Møller–Plesset perturbation method (MP2), both of which are size consistent. We have applied this GVB-BCPT2 method to investigate the equilibrium distances and spectroscopic constants of 7 diatomic molecules, conformational energy differences of 8 small molecules, and bond-breaking potential energy profiles in 3 systems. GVB-BCPT2 is demonstrated to have noticeably better performance than MP2 for systems with significant multi-reference character, and provide reasonably accurate results for some systems with large active spaces, which are beyond the capability of all CASSCF-based methods

  20. Resonating Valence Bonds and Mean-Field d-Wave Superconductivity in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Black-Schaffer, Annica M.

    2010-04-27

    We investigate the possibility of inducing superconductivity in a graphite layer by electronic correlation effects. We use a phenomenological microscopic Hamiltonian which includes nearest neighbor hopping and an interaction term which explicitly favors nearest neighbor spin-singlets through the well-known resonance valence bond (RVB) character of planar organic molecules. Treating this Hamiltonian in mean-field theory, allowing for bond-dependent variation of the RVB order parameter, we show that both s- and d-wave superconducting states are possible. The d-wave solution belongs to a two-dimensional representation and breaks time reversal symmetry. At zero doping there exists a quantum critical point at the dimensionless coupling J/t = 1.91 and the s- and d-wave solutions are degenerate for low temperatures. At finite doping the d-wave solution has a significantly higher T{sub c} than the s-wave solution. By using density functional theory we show that the doping induced from sulfur absorption on a graphite layer is enough to cause an electronically driven d-wave superconductivity at graphite-sulfur interfaces. We also discuss applying our results to the case of the intercalated graphites as well as the validity of a mean-field approach.

  1. Exploring the Nature of the H[subscript 2] Bond. 1. Using Spreadsheet Calculations to Examine the Valence Bond and Molecular Orbital Methods

    Science.gov (United States)

    Halpern, Arthur M.; Glendening, Eric D.

    2013-01-01

    A three-part project for students in physical chemistry, computational chemistry, or independent study is described in which they explore applications of valence bond (VB) and molecular orbital-configuration interaction (MO-CI) treatments of H[subscript 2]. Using a scientific spreadsheet, students construct potential-energy (PE) curves for several…

  2. Structural and magnetic properties of Ba2LuMoO6: a valence bond glass.

    Science.gov (United States)

    Coomer, Fiona C; Cussen, Edmund J

    2013-02-27

    We report here the synthesis of the site ordered double perovskite Ba(2)LuMoO(6). Rietveld refinement of room temperature powder x-ray diffraction measurements indicates that it crystallizes in the cubic space group Fm3m, with a = 8.3265(1) Å. Powder neutron diffraction data indicate that, unusually, this cubic symmetry is maintained down to 2 K, with [Formula: see text], Mo(5+) ions situated on the frustrated face-centred cubic lattice. Despite dc-susceptibility measurements showing Curie-Weiss behaviour with strong antiferromagnetic interactions at T ≥ 200 K, there is no evidence of long range magnetic ordering at 2 K. At T ≤ 50 K, susceptibility measurements indicate a loss in moment to ∼18% of the expected value, and there is a corresponding loss in the magnitude of the magnetic exchange. The structural and magnetic properties of this compound are compared with the related compound Ba(2)YMoO(6), which is a valence bond glass. PMID:23343826

  3. Structural and magnetic properties of Ba2LuMoO6: a valence bond glass

    International Nuclear Information System (INIS)

    We report here the synthesis of the site ordered double perovskite Ba2LuMoO6. Rietveld refinement of room temperature powder x-ray diffraction measurements indicates that it crystallizes in the cubic space group F m 3-bar m, with a = 8.3265(1) Å. Powder neutron diffraction data indicate that, unusually, this cubic symmetry is maintained down to 2 K, with S= 1/2 , Mo5+ ions situated on the frustrated face-centred cubic lattice. Despite dc-susceptibility measurements showing Curie–Weiss behaviour with strong antiferromagnetic interactions at T ≥ 200 K, there is no evidence of long range magnetic ordering at 2 K. At T ≤ 50 K, susceptibility measurements indicate a loss in moment to ∼18% of the expected value, and there is a corresponding loss in the magnitude of the magnetic exchange. The structural and magnetic properties of this compound are compared with the related compound Ba2YMoO6, which is a valence bond glass. (fast track communication)

  4. Comment on ''Valence QCD: Connecting QCD to the quark model''

    International Nuclear Information System (INIS)

    The author criticize certain conclusions about the physics of hadrons drawn from a ''valence QCD'' approximation to QCD. Lattice QCD is not just useful as a technique for calculating strong interaction observables like the proton mass: it can also be used to help understand QCD. This is the goal of the work described in reference 1. Its authors present a field theory which they call valence QCD (vQCD) which they hope can be identified with the valence quark model. The key feature built into vQCD is a form of suppression of Z-graphs, i.e., of quarks propagating backward in time. The authors make sound arguments for the importance of trying to capture the essence of the quark model in a field-theoretic framework, and present some interesting results (both theoretical and numerical) on vQCD. This comment is not directed at the goals of vQCD but rather at certain conclusions about the physics of hadrons which the authors have drawn from their work which the author considers unjustified. Foremost among these is the claim highlighted in their abstract that baryon hyperfine interactions are ''largely attributed to the Goldstone boson exchanges between the quarks'' and not to standard one-gluon-exchange (OGE) forces

  5. Emergence of superconductivity, valence bond order and Mott insulators in Pd[(dmit)2] based organic salts

    Science.gov (United States)

    Kee, Hae-Young

    2014-03-01

    The EtMe3P and EtMe3Sb nearly triangular organic salts are distinguished from most other Pd[(dmit)2] based salts, as they display valence bond and no long range order, respectively. Under pressure, a superconducting phase is revealed in EtMe3P near the boundary of valence bond order. We use slave-rotor theory with an enlarged unit cell to study competition between uniform and broken translational symmetry states, offering a theoretical framework capturing the superconducting, valence bond order, spin liquid, and metallic phases on an isotropic triangular lattice. Our finite temperature phase diagram manifests a remarkable resemblance to the phase diagram of the EtMe3P salt, where the re-entrant transitions of the type insulator-metal-insulator can be explained by an entropy difference between metal and the U(1) spin liquid. We find that the superconducting pairing symmetry is d +/- id , and predict different temperature dependences of the specific heat between the spin liquid and metal. Canadian Institute for Advanced Research, NSERC of Canada.

  6. Intramolecular hydrogen bond: Can it be part of the basis set of valence internal coordinates in normal mode analysis?

    Indian Academy of Sciences (India)

    Sarvesh Kumar Pandey; Prasanta Das; Puspendu K Das; Elangannan Arunan; Sadasivam Manogaran

    2015-06-01

    It has been shown earlier1 that the relaxed force constants (RFCs) could be used as a measure of bond strength only when the bonds form a part of the complete valence internal coordinates (VIC) basis. However, if the bond is not a part of the complete VIC basis, its RFC is not necessarily a measure of bond strength. Sometimes, it is possible to have a complete VIC basis that does not contain the intramolecular hydrogen bond (IMHB) as part of the basis. This means the RFC of IMHB is not necessarily a measure of bond strength. However, we know that IMHB is a weak bond and hence its RFC has to be a measure of bond strength. We resolve this problem of IMHB not being part of the complete basis by postulating `equivalent’ basis sets where IMHB is part of the basis at least in one of the equivalent sets of VIC. As long as a given IMHB appears in one of the equivalent complete VIC basis sets, its RFC could be used as a measure of bond strength parameter.

  7. Multistate empirical valence bond study of temperature and confinement effects on proton transfer in water inside hydrophobic nanochannels.

    Science.gov (United States)

    Tahat, Amani; Martí, Jordi

    2016-07-01

    Microscopic characteristics of an aqueous excess proton in a wide range of thermodynamic states, from low density amorphous ices (down to 100 K) to high temperature liquids under the critical point (up to 600 K), placed inside hydrophobic graphene slabs at the nanometric scale (with interplate distances between 3.1 and 0.7 nm wide) have been analyzed by means of molecular dynamics simulations. Water-proton and carbon-proton forces were modeled with a multistate empirical valence bond method. Densities between 0.07 and 0.02 Å(-3) have been considered. As a general trend, we observed a competition between effects of confinement and temperature on structure and dynamical properties of the lone proton. Confinement has strong influence on the local structure of the proton, whereas the main effect of temperature on proton properties is observed on its dynamics, with significant variation of proton transfer rates, proton diffusion coefficients, and characteristic frequencies of vibrational motions. Proton transfer is an activated process with energy barriers between 1 and 10 kJ/mol for both proton transfer and diffusion, depending of the temperature range considered and also on the interplate distance. Arrhenius-like behavior of the transfer rates and of proton diffusion are clearly observed for states above 100 K. Spectral densities of proton species indicated that in all states Zundel-like and Eigen-like complexes survive at some extent. © 2016 Wiley Periodicals, Inc. PMID:27189810

  8. Actinides in silicate glasses and melts and on mineral surfaces: information on local co-ordination environments from XAFS spectroscopy and bond valence theory

    International Nuclear Information System (INIS)

    The impact of actinides on the environment is mitigated by their interaction with particle surfaces and by incorporation into suitable waste forms. In both cases, a fundamental knowledge of the local co-ordination environment of actinide ions is essential for understanding their stability in various near-surface environments under a range of conditions. When actinide ions are sorbed on mineral surfaces, the extent to which the ions are immobilised depends on the type of surface complex or solid precipitate that forms. When incorporated into a glass or crystalline waste form, the stability of the actinide will depend in part on its redox state and local co-ordination environment. In both cases, XAFS spectroscopy can provide unique information on the number and types of first and, in certain cases, more distant neighbours, and their geometric arrangement (including inter-atomic distances and a measure of their disorder). When this structural information from XAFS spectroscopy is combined with Pauling bond valence theory and modem bond valences corrected for bond length variations, it is also possible to develop plausible models for their medium-range co-ordination environments (out to ≅ 4 Angstrom radial distance around the actinide) for both sorbed actinide ions and those present in a silicate glass or melt. We discuss results from several XAFS studies of the naturally occurring actinides uranium and thorium in sorption samples, silicate glasses and silicate melts at high temperature. (authors)

  9. Valence tautomerism in synthetic models of cytochrome P450.

    Science.gov (United States)

    Das, Pradip Kumar; Samanta, Subhra; McQuarters, Ashley B; Lehnert, Nicolai; Dey, Abhishek

    2016-06-14

    CytP450s have a cysteine-bound heme cofactor that, in its as-isolated resting (oxidized) form, can be conclusively described as a ferric thiolate species. Unlike the native enzyme, most synthetic thiolate-bound ferric porphyrins are unstable in air unless the axial thiolate ligand is sterically protected. Spectroscopic investigations on a series of synthetic mimics of cytP450 indicate that a thiolate-bound ferric porphyrin coexists in organic solutions at room temperature (RT) with a thiyl-radical bound ferrous porphyrin, i.e., its valence tautomer. The ferric thiolate state is favored by greater enthalpy and is air stable. The ferrous thiyl state is favored by entropy, populates at RT, and degrades in air. These ground states can be reversibly interchanged at RT by the addition or removal of water to the apolar medium. It is concluded that hydrogen bonding and local electrostatics protect the resting oxidized cytP450 active site from degradation in air by stabilizing the ferric thiolate ground state in contrast to its synthetic analogs. PMID:27302948

  10. Thermomechanical properties of graphene: valence force field model approach

    International Nuclear Information System (INIS)

    Using the valence force field model of Perebeinos and Tersoff (2009 Phys. Rev. B 79 241409(R)), different energy modes of suspended graphene subjected to tensile or compressive strain are studied. By carrying out Monte Carlo simulations it is found that: (i) only for small strains (|ε| ⪅ 0.02) is the total energy symmetrical in the strain, while it behaves completely differently beyond this threshold; (ii) the important energy contributions in stretching experiments are stretching, angle bending, an out-of-plane term, and a term that provides repulsion against π-π misalignment; (iii) in compressing experiments the two latter terms increase rapidly, and beyond the buckling transition stretching and bending energies are found to be constant; (iv) from stretching-compressing simulations we calculated the Young’s modulus at room temperature 350 ± 3.15 N m-1, which is in good agreement with experimental results (340 ± 50 N m-1) and with ab initio results (322-353) N m-1; (v) molar heat capacity is estimated to be 24.64 J mol-1 K-1 which is comparable with the Dulong-Petit value, i.e. 24.94 J mol-1 K-1, and is almost independent of the strain; (vi) nonlinear scaling properties are obtained from height-height correlations at finite temperature; (vii) the used valence force field model results in a temperature independent bending modulus for graphene, and (viii) the Grüneisen parameter is estimated to be 0.64. (paper)

  11. In-Medium Pion Valence Distributions in a Light-Front Model

    CERN Document Server

    de Melo, J P B C; Ahmed, I

    2016-01-01

    Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.

  12. Analysis of the bond-valence method for calculating (29) Si and (31) P magnetic shielding in covalent network solids.

    Science.gov (United States)

    Holmes, Sean T; Alkan, Fahri; Iuliucci, Robbie J; Mueller, Karl T; Dybowski, Cecil

    2016-07-01

    (29) Si and (31) P magnetic-shielding tensors in covalent network solids have been evaluated using periodic and cluster-based calculations. The cluster-based computational methodology employs pseudoatoms to reduce the net charge (resulting from missing co-ordination on the terminal atoms) through valence modification of terminal atoms using bond-valence theory (VMTA/BV). The magnetic-shielding tensors computed with the VMTA/BV method are compared to magnetic-shielding tensors determined with the periodic GIPAW approach. The cluster-based all-electron calculations agree with experiment better than the GIPAW calculations, particularly for predicting absolute magnetic shielding and for predicting chemical shifts. The performance of the DFT functionals CA-PZ, PW91, PBE, rPBE, PBEsol, WC, and PBE0 are assessed for the prediction of (29) Si and (31) P magnetic-shielding constants. Calculations using the hybrid functional PBE0, in combination with the VMTA/BV approach, result in excellent agreement with experiment. © 2016 Wiley Periodicals, Inc. PMID:27117609

  13. Photoemission signatures of valence-bond stripes in cuprates: Long-range vs. short-range order

    International Nuclear Information System (INIS)

    Recent experiments indicate that the tendency toward the formation of unidirectional charge density waves ('stripes') is common to various underdoped cuprates. We discuss momentum-resolved spectral properties of valence-bond stripes, comparing the situations of ideal and short-range stripe order, the latter being relevant for weak and/or disorder-pinned stripes. We find clear signatures of ordered stripes, although matrix element effects suppress most shadow band features. With decreasing stripe correlation length, stripe signatures are quickly washed out, the only remaining effect being a broadening of antinodal quasiparticles. This insensitivity of photoemission to short-range stripe order may be employed to distinguish it from nematic order, e.g. in underdoped YBa2Cu3O6+δ.

  14. Photoemission signatures of valence-bond stripes in cuprates: Long-range vs. short-range order

    Energy Technology Data Exchange (ETDEWEB)

    Wollny, Alexander [Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Vojta, Matthias, E-mail: vojta@thp.uni-koeln.d [Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany)

    2009-10-15

    Recent experiments indicate that the tendency toward the formation of unidirectional charge density waves ('stripes') is common to various underdoped cuprates. We discuss momentum-resolved spectral properties of valence-bond stripes, comparing the situations of ideal and short-range stripe order, the latter being relevant for weak and/or disorder-pinned stripes. We find clear signatures of ordered stripes, although matrix element effects suppress most shadow band features. With decreasing stripe correlation length, stripe signatures are quickly washed out, the only remaining effect being a broadening of antinodal quasiparticles. This insensitivity of photoemission to short-range stripe order may be employed to distinguish it from nematic order, e.g. in underdoped YBa{sub 2}Cu{sub 3}O{sub 6+d}elta.

  15. d-wave stripes in cuprates: Valence bond order coexisting with nodal quasiparticles

    Energy Technology Data Exchange (ETDEWEB)

    Vojta, Matthias [Institut fuer Theoretische Physik, Universitaet Koeln, 50937 Koeln (Germany)

    2008-07-01

    We point out that unidirectional bond-centered charge-density-wave states in cuprates involve electronic order in both s- and d-wave channels, with non-local Coulomb repulsion suppressing the s-wave component. The resulting bond-charge-density wave, coexisting with superconductivity, is compatible with momentum-space features seen in recent photoemission and tunneling data and as well as in neutron-scattering measurements, once long-range order is destroyed by slow fluctuations or glassy disorder.

  16. d-wave stripes in cuprates: Valence bond order coexisting with nodal quasiparticles

    International Nuclear Information System (INIS)

    We point out that unidirectional bond-centered charge-density-wave states in cuprates involve electronic order in both s- and d-wave channels, with non-local Coulomb repulsion suppressing the s-wave component. The resulting bond-charge-density wave, coexisting with superconductivity, is compatible with momentum-space features seen in recent photoemission and tunneling data and as well as in neutron-scattering measurements, once long-range order is destroyed by slow fluctuations or glassy disorder

  17. Qgui: A high-throughput interface for automated setup and analysis of free energy calculations and empirical valence bond simulations in biological systems.

    Science.gov (United States)

    Isaksen, Geir Villy; Andberg, Tor Arne Heim; Åqvist, Johan; Brandsdal, Bjørn Olav

    2015-07-01

    Structural information and activity data has increased rapidly for many protein targets during the last decades. In this paper, we present a high-throughput interface (Qgui) for automated free energy and empirical valence bond (EVB) calculations that use molecular dynamics (MD) simulations for conformational sampling. Applications to ligand binding using both the linear interaction energy (LIE) method and the free energy perturbation (FEP) technique are given using the estrogen receptor (ERα) as a model system. Examples of free energy profiles obtained using the EVB method for the rate-limiting step of the enzymatic reaction catalyzed by trypsin are also shown. In addition, we present calculation of high-precision Arrhenius plots to obtain the thermodynamic activation enthalpy and entropy with Qgui from running a large number of EVB simulations. PMID:26080356

  18. Chemical-shift tensors of heavy nuclei in network solids: a DFT/ZORA investigation of (207)Pb chemical-shift tensors using the bond-valence method.

    Science.gov (United States)

    Alkan, Fahri; Dybowski, C

    2015-10-14

    Cluster models are used in calculation of (207)Pb NMR magnetic-shielding parameters of α-PbO, β-PbO, Pb3O4, Pb2SnO4, PbF2, PbCl2, PbBr2, PbClOH, PbBrOH, PbIOH, PbSiO3, and Pb3(PO4)2. We examine the effects of cluster size, method of termination of the cluster, charge on the cluster, introduction of exact exchange, and relativistic effects on calculation of magnetic-shielding tensors with density functional theory. Proper termination of the cluster for a network solid, including approximations such as compensation of charge by the bond-valence (BV) method, is essential to provide results that agree with experiment. The inclusion of relativistic effects at the spin-orbit level for such heavy nuclei is an essential factor in achieving agreement with experiment. PMID:26345261

  19. Insights into the Electronic Structure of Ozone and Sulfur Dioxide from Generalized Valence Bond Theory: Addition of Hydrogen Atoms.

    Science.gov (United States)

    Lindquist, Beth A; Takeshita, Tyler Y; Dunning, Thom H

    2016-05-01

    Ozone (O3) and sulfur dioxide (SO2) are valence isoelectronic species, yet their properties and reactivities differ dramatically. In particular, O3 is highly reactive, whereas SO2 is chemically relatively stable. In this paper, we investigate serial addition of hydrogen atoms to both the terminal atoms of O3 and SO2 and to the central atom of these species. It is well-known that the terminal atoms of O3 are much more amenable to bond formation than those of SO2. We show that the differences in the electronic structure of the π systems in the parent triatomic species account for the differences in the addition of hydrogen atoms to the terminal atoms of O3 and SO2. Further, we find that the π system in SO2, which is a recoupled pair bond dyad, facilitates the addition of hydrogen atoms to the sulfur atom, resulting in stable HSO2 and H2SO2 species. PMID:27070292

  20. 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.

  1. Intramolecular C-H bond activation and redox isomerization across two-electron mixed valence diiridium cores.

    Energy Technology Data Exchange (ETDEWEB)

    Esswein, A. J.; Veige, A. S.; Piccoli, P. M. B.; Schultz, A. J.; Nocera, D. G.; MIT

    2008-03-24

    Metal-metal cooperativity enables the reaction of carbon-based substrates at diiridium two-electron mixed valence centers. Arylation of Ir{sub 2}{sup 0,II}(tfepma){sub 3}Cl{sub 2} (1) (tfepma = bis[(bistrifluoroethoxy)phosphino]methylamine) with RMgBr (R = C{sub 6}H{sub 5} and C{sub 6}D{sub 5}) is followed by C-H bond activation to furnish the bridging benzyne complex Ir{sub 2}II,II(tfepma){sub 3}({mu}-C{sub 6}H4)(C{sub 6}H{sub 5})H (2), as the kinetic product. At ambient temperature, 2 isomerizes to Ir{sub 2}{sup I,III}(tfepma){sub 3}({mu}-C{sub 6}H4)(C{sub 6}H{sub 5})H (3) (k{sub obs} = 9.57 {+-} 0.10 x 10{sup -5} s{sup -1} at 31.8 C, {Delta}H{sup {+-}} = 21.7 {+-} 0.3 kcal/mol, {Delta}S{sup {+-}} = -7.4 {+-} 0.9 eu), in which the benzyne moiety is conserved and the Ir{sup III} center is ligated by terminal hydride and phenyl groups. The same reaction course is observed for arylation of 1 with C{sub 6}D{sub 5}MgBr to produce 2-d{sub 10} and 3-d{sub 10} accompanied by an inverse isotope effect, k{sub h}/k{sub d} = 0.44 (k{sub obs} = 2.17 {+-} 0.10 x 10{sup -4} s{sup -1} in C{sub 6}D{sub 6} solution at 31.8 C, {Delta}H{sup {+-}} = 24.9 {+-} 0.7 kcal/mol, {Delta}S{sup {+-}} = -6.4 {+-} 2.4 eu). 2 reacts swiftly with hydrogen to provide Ir{sub 2}{sup II,II}(tfepma){sub 3}H{sub 4} as both the syn and anti isomers (4-syn and 4-anti, respectively). The hydrides of 4-syn were directly located by neutron diffraction analysis. X-ray crystallographic examination of 2, 2-d{sub 10}, 3, and 4-syn indicates that cooperative reactivity at the bimetallic diiridium core is facilitated by the ability of the two-electron mixed valence framework to accommodate the oxidation state changes and ligand rearrangements attendant to the reaction of the substrate.

  2. Bond graph modeling of centrifugal compression systems

    OpenAIRE

    Uddin, Nur; Gravdahl, Jan Tommy

    2015-01-01

    A novel approach to model unsteady fluid dynamics in a compressor network by using a bond graph is presented. The model is intended in particular for compressor control system development. First, we develop a bond graph model of a single compression system. Bond graph modeling offers a different perspective to previous work by modeling the compression system based on energy flow instead of fluid dynamics. Analyzing the bond graph model explains the energy flow during compressor surge. Two pri...

  3. A minimalistic approach to static and dynamic electron correlations: Amending generalized valence bond method with extended random phase approximation correlation correction

    Science.gov (United States)

    Chatterjee, Koushik; Pastorczak, Ewa; Jawulski, Konrad; Pernal, Katarzyna

    2016-06-01

    A perfect-pairing generalized valence bond (GVB) approximation is known to be one of the simplest approximations, which allows one to capture the essence of static correlation in molecular systems. In spite of its attractive feature of being relatively computationally efficient, this approximation misses a large portion of dynamic correlation and does not offer sufficient accuracy to be generally useful for studying electronic structure of molecules. We propose to correct the GVB model and alleviate some of its deficiencies by amending it with the correlation energy correction derived from the recently formulated extended random phase approximation (ERPA). On the examples of systems of diverse electronic structures, we show that the resulting ERPA-GVB method greatly improves upon the GVB model. ERPA-GVB recovers most of the electron correlation and it yields energy barrier heights of excellent accuracy. Thanks to a balanced treatment of static and dynamic correlation, ERPA-GVB stays reliable when one moves from systems dominated by dynamic electron correlation to those for which the static correlation comes into play.

  4. Levels of valence

    Directory of Open Access Journals (Sweden)

    VeraShuman

    2013-05-01

    Full Text Available The distinction between the positive and the negative is fundamental in our emotional life. In appraisal theories, in particular in the component process model of emotion (Scherer, 1984, 2010, qualitatively different types of valence are proposed based on appraisals of (unpleasantness, goal obstructiveness/conduciveness, low or high power, self- (incongruence, and moral badness/goodness. This multifaceted conceptualization of valence is highly compatible with the frequent observation of mixed feelings in real life. However, it seems to contradict the one-dimensional conceptualization of valence often encountered in psychological theories, and the notion of valence as a common currency used to explain choice behavior. Here, we propose a framework to integrate the seemingly disparate conceptualizations of multifaceted valence and one-dimensional valence by suggesting that valence should be conceived at different levels, micro and macro. Micro-valences correspond to qualitatively different types of evaluations, potentially resulting in mixed feelings, whereas one-dimensional macro-valence corresponds to an integrative “common currency” to compare alternatives for choices. We propose that conceptualizing levels of valence may focus research attention on the mechanisms that relate valence at one level (micro to valence at another level (macro, leading to new hypotheses and addressing various concerns that have been raised about the valence concept, such as the valence-emotion relation.

  5. Valence-bond crystals in the kagomé spin-1/2 Heisenberg antiferromagnet: a symmetry classification and projected wave function study

    International Nuclear Information System (INIS)

    In this paper, we do a complete classification of valence-bond crystals (VBCs) on the kagomé lattice based on general arguments of symmetry only and thus identify many new VBCs for different unit cell sizes. For the spin-1/2 Heisenberg antiferromagnet, we study the relative energetics of competing gapless spin liquids (SLs) and VBC phases within the class of Gutzwiller-projected fermionic wave functions using variational Monte Carlo techniques, hence implementing exactly the constraint of one fermion per site. By using a state-of-the-art optimization method, we conclusively show that the U(1) Dirac SL is remarkably stable towards dimerizing into all 6-, 12- and 36-site unit cell VBCs. This stability is also preserved on addition of a next-nearest-neighbor super-exchange coupling of both antiferromagnetic and ferromagnetic (FM) type. However, we find that a 36-site unit cell VBC is stabilized on addition of a very small next-nearest-neighbor FM super-exchange coupling, i.e. |J2| ≈ 0.045, and this VBC is the same in terms of space-group symmetry as that obtained in an effective quantum dimer model study. It breaks reflection symmetry, has a nontrivial flux pattern and is a strong dimerization of the uniform RVB SL. (paper)

  6. Bond formation effects on the metal-insulator transition in the half-filled kagome Hubbard model

    Science.gov (United States)

    Higa, Ryota; Asano, Kenichi

    2016-06-01

    We study the metal-insulator transition in the half-filled Hubbard model on a Kagome lattice using the variational cluster approximation. The strong coupling limit of the model corresponds to the S =1 /2 Kagome Heisenberg antiferromagnet, which is known to have a singlet ground state, although its detail is still debated. As the results of the cluster methods generally depend much on the choice of the unit cluster, we have chosen the clusters that are compatible with these singlet ground states in the strong coupling case found so far, which basically consist of even number of sites. It is found that the correlated electrons on the Kagome lattice have a strong tendency to form valence-bond structures, which are the resonation of electrons on a single bond or several bonds forming loops. The zero-temperature metal-insulator transition at some interaction strength is possibly driven by the formation of such short range valence bonds and shows a second order character, which is distinctive from the Brinkman-Rice scenario. The electrons on these valence bonds further localizes onto each site as the interaction increases, and the valence bonds of electrons finally turn into magnetic singlet bonds between localized S =1 /2 spins, which are consistent with the ground states of the Kagome antiferromagnet.

  7. Generalized valence bond description of the ground states (X(1)Σg(+)) of homonuclear pnictogen diatomic molecules: N2, P2, and As2.

    Science.gov (United States)

    Xu, Lu T; Dunning, Thom H

    2015-06-01

    The ground state, X1Σg+, of N2 is a textbook example of a molecule with a triple bond consisting of one σ and two π bonds. This assignment, which is usually rationalized using molecular orbital (MO) theory, implicitly assumes that the spins of the three pairs of electrons involved in the bonds are singlet-coupled (perfect pairing). However, for a six-electron singlet state, there are five distinct ways to couple the electron spins. The generalized valence bond (GVB) wave function lifts this restriction, including all of the five spin functions for the six electrons involved in the bond. For N2, we find that the perfect pairing spin function is indeed dominant at Re but that it becomes progressively less so from N2 to P2 and As2. Although the perfect pairing spin function is still the most important spin function in P2, the importance of a quasi-atomic spin function, which singlet couples the spins of the electrons in the σ orbitals while high spin coupling those of the electrons in the π orbitals on each center, has significantly increased relative to N2 and, in As2, the perfect pairing and quasi-atomic spin couplings are on essentially the same footing. This change in the spin coupling of the electrons in the bonding orbitals down the periodic table may contribute to the rather dramatic decrease in the strengths of the Pn2 bonds from N2 to As2 as well as in the increase in their chemical reactivity and should be taken into account in more detailed analyses of the bond energies in these species. We also compare the spin coupling in N2 with that in C2, where the quasi-atomic spin coupling dominants around Re. PMID:26575549

  8. Bond diluted anisotropic quantum Heisenberg model

    International Nuclear Information System (INIS)

    Effects of the bond dilution on the critical temperatures, phase diagrams and the magnetization behaviors of the isotropic and anisotropic quantum Heisenberg model have been investigated in detail. For the isotropic case, bond percolation threshold values have been determined for several numbers of two (2D) and three (3D) dimensional lattices. In order to investigate the effect of the anisotropy in the exchange interaction on the results obtained for the isotropic model, a detailed investigation has been made on a honeycomb lattice. Some interesting results, such as second order reentrant phenomena in the phase diagrams have been found. - Highlights: • Anisotropic quantum Heisenberg model with bond dilution investigated. • Bond percolation threshold values given for 2D and 3D lattices in isotropic case. • Phase diagrams and ground state magnetizations investigated in detail. • Variation of the bond percolation threshold values with anisotropy determined

  9. Valency and molecular structure

    CERN Document Server

    Cartmell, E

    1977-01-01

    Valency and Molecular Structure, Fourth Edition provides a comprehensive historical background and experimental foundations of theories and methods relating to valency and molecular structures. In this edition, the chapter on Bohr theory has been removed while some sections, such as structures of crystalline solids, have been expanded. Details of structures have also been revised and extended using the best available values for bond lengths and bond angles. Recent developments are mostly noted in the chapter on complex compounds, while a new chapter has been added to serve as an introduction t

  10. Classification model of arousal and valence mental states by EEG signals analysis and Brodmann correlations

    Directory of Open Access Journals (Sweden)

    Adrian Rodriguez Aguinaga

    2015-06-01

    Full Text Available This paper proposes a methodology to perform emotional states classification by the analysis of EEG signals, wavelet decomposition and an electrode discrimination process, that associates electrodes of a 10/20 model to Brodmann regions and reduce computational burden. The classification process were performed by a Support Vector Machines Classification process, achieving a 81.46 percent of classification rate for a multi-class problem and the emotions modeling are based in an adjusted space from the Russell Arousal Valence Space and the Geneva model.

  11. On the efficiency of VBSCF algorithms, a comment on "An efficient algorithm for energy gradients and orbital optimization in valence bond theory".

    Science.gov (United States)

    van Lenthe, J H; Broer-Braam, H B; Rashid, Z

    2012-03-30

    We comment on the paper [Song et al., J. Comput. Chem. 2009, 30, 399]. and discuss the efficiency of the orbital optimization and gradient evaluation in the Valence Bond Self Consistent Field (VBSCF) method. We note that Song et al. neglect to properly reference Broer et al., who published an algorithm [Broer and Nieuwpoort, Theor. Chim. Acta 1988, 73, 405] to use a Fock matrix to compute a matrix element between two different determinants, which can be used for an orbital optimization. Further, Song et al. publish a misleading comparison with our VBSCF algorithm [Dijkstra and van Lenthe, J. Chem. Phys. 2000, 113, 2100; van Lenthe et al., Mol. Phys. 1991, 73, 1159] to enable them to favorably compare their algorithm with ours. We give detail timings in terms of different orbital types in the calculation and actual timings for the example cases. PMID:22278948

  12. Bond diluted anisotropic quantum Heisenberg model

    OpenAIRE

    Akıncı, Ümit

    2013-01-01

    Effects of the bond dilution on the critical temperatures, phase diagrams and the magnetization behaviors of the isotropic and anisotropic quantum Heisenberg model have been investigated in detail. For the isotropic case, bond percolation threshold values have been determined for several numbers of two (2D) and three (3D) dimensional lattices. In order to investigate the effect of the anisotropy in the exchange interaction on the results obtained for the isotropic model, a detailed investigat...

  13. A model for the relative intensities among ion pair → valence transitions in the heavier halogens and rare gas halides

    Science.gov (United States)

    Jewsbury, Philip; Lawley, Kenneth

    1990-03-01

    The separated atom or ( JAMAJBMB) coupling scheme is applied to the electronic structure of both ion pair and valence states of the heavier halogens and rare gas halides. Relative transition moments from low vibrational levels of selected ion pair states to all the valence states and the resulting radiative lifetimes are derived. σ↔σ electron transfer between atomic orbitals is assumed for parallel transitions. Russell-Saunders coupling is used for the atomic or ionic basis functions in the reference model. Departures from the model arising from partial jj coupling in the halogen positive ions and from intramolecular electrostatic effects each produce characteristic changes in the relative intensities of the various fluorescent systems from a given ion pair state. The effect of J and MJ state mixing between asymptotically degenerate valence states is discussed and ion pair → valence transition intensities are shown to be a sensitive function of this mixing.

  14. Mechatronic modeling and simulation using bond graphs

    CERN Document Server

    Das, Shuvra

    2009-01-01

    Bond graphs are especially well-suited for mechatronic systems, as engineering system modeling is best handled using a multidisciplinary approach. Bond graphing permits one to see the separate components of an engineering system as a unified whole, and allows these components to be categorized under a few generalized elements, even when they come from different disciplines. In addition to those advantages, the bond graph offers a visual representation of a system from which derivation of the governing equations is algorithmic. This makes the design process accessible to beginning readers, prov

  15. Valence Band Structure of InAs1-xBix and InSb1-xBix Alloy Semiconductors Calculated Using Valence Band Anticrossing Model

    Directory of Open Access Journals (Sweden)

    D. P. Samajdar

    2014-01-01

    Full Text Available The valence band anticrossing model has been used to calculate the heavy/light hole and spin-orbit split-off energies in InAs1-xBix and InSb1-xBix alloy systems. It is found that both the heavy/light hole, and spin-orbit split E+ levels move upwards in energy with an increase in Bi content in the alloy, whereas the split E− energy for the holes shows a reverse trend. The model is also used to calculate the reduction of band gap energy with an increase in Bi mole fraction. The calculated values of band gap variation agree well with the available experimental data.

  16. Synthesis, Characterization Studies and Bond Valence Sum (BVS analysis on 2:1 Adducts involving Zinc(IIdithiocarbamates and 4,4’-Bipyridine

    Directory of Open Access Journals (Sweden)

    Arumugam Manohar

    2015-06-01

    Full Text Available 2:1 adducts involving [Zn(dtc2]2 (dtc- = pipdtc-, H10C5NCS-2; dnpdtc-, (H3CCH2CH22NCS-2; dedtc-, (H5C22NCS-2; dmdtc-, (H3C2NCS-2; nmedtc-, HOCH2CH2(CH3NCS-2; deadtc-, (HOCH2CH22NCS-2 and 4,4' – bipyridine were prepared and characterized by elemental analyses, IR, UV-Visible, Cyclic voltammetric and thermal studies. IR spectra of the complexes show the reduction in the thioureide stretching frequency due to the increase in coordination around the zinc ion and the resultant increase in electron density. The charge transfer transitions are observed in the region 260 – 320 nm by electronic spectra. Thermal studies show a single stage weight loss. The cyclic voltammetric study on the complexes show an increase of electron density on zinc in the adducts compared to [Zn(dtc2]2. The bond valence sum(BVS analysis shows the values to be close to '2', which is equivalent to the formal oxidation state of zinc in the zinc complexes.

  17. Modeling the Hydrogen Bond within Molecular Dynamics

    Science.gov (United States)

    Lykos, Peter

    2004-01-01

    The structure of a hydrogen bond is elucidated within the framework of molecular dynamics based on the model of Rahman and Stillinger (R-S) liquid water treatment. Thus, undergraduates are exposed to the powerful but simple use of classical mechanics to solid objects from a molecular viewpoint.

  18. Valence-dependent influence of serotonin depletion on model-based choice strategy.

    Science.gov (United States)

    Worbe, Y; Palminteri, S; Savulich, G; Daw, N D; Fernandez-Egea, E; Robbins, T W; Voon, V

    2016-05-01

    Human decision-making arises from both reflective and reflexive mechanisms, which underpin goal-directed and habitual behavioural control. Computationally, these two systems of behavioural control have been described by different learning algorithms, model-based and model-free learning, respectively. Here, we investigated the effect of diminished serotonin (5-hydroxytryptamine) neurotransmission using dietary tryptophan depletion (TD) in healthy volunteers on the performance of a two-stage decision-making task, which allows discrimination between model-free and model-based behavioural strategies. A novel version of the task was used, which not only examined choice balance for monetary reward but also for punishment (monetary loss). TD impaired goal-directed (model-based) behaviour in the reward condition, but promoted it under punishment. This effect on appetitive and aversive goal-directed behaviour is likely mediated by alteration of the average reward representation produced by TD, which is consistent with previous studies. Overall, the major implication of this study is that serotonin differentially affects goal-directed learning as a function of affective valence. These findings are relevant for a further understanding of psychiatric disorders associated with breakdown of goal-directed behavioural control such as obsessive-compulsive disorders or addictions. PMID:25869808

  19. ESTIMATING STRUCTURAL MODELS OF CORPORATE BOND PRICES

    OpenAIRE

    Max Bruche

    2006-01-01

    One of the strengths of structural models (or firm-value based models) of credit (e.g. Merton, 1974) as opposed to reduced-form models (e.g. Jarrow and Turnbull, 1995) is that they directly link the price of equity to default probabilities, and hence to the price of corporate bonds (and credit derivatives). Yet when these models are estimated on actual data, the existence of data other than equity prices is typically ignored. This paper describes how all available price data (equity prices, b...

  20. LAMMPS Framework for Dynamic Bonding and an Application Modeling DNA

    DEFF Research Database (Denmark)

    Svaneborg, Carsten

    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...

  1. Bond-Ordering Model for the Glass Transition

    OpenAIRE

    Davatolhagh, Saeid; Patton, Bruce R.

    2000-01-01

    We consider the idea of bond ordering as a model for glass transition: a generic covalently bonded liquid may substantially reduce its energy through bond ordering, without undergoing significant structural order. This concept is developed for a model system using quantities such as a bond order parameter and susceptibility which provide new identification for calorimetric glass transition temperature. Monte Carlo simulation results exhibit bond ordering at intermediate temperatures uncorrela...

  2. Effective interactions for valence-hole nuclei with modern meson-exchange potential models

    International Nuclear Information System (INIS)

    Within the framework of the folded-diagram theory, the authors have studied the effective interaction appropriate for hole-hole nuclei in the mass regions of 16O and 40Ca, using the Bonn and Paris potential models. To sum up the folded diagrams the renormalization procedure of Lee and Suzuki has been employed, using a so-called Q-box in which were included all one-body and two-body irreducible valence-linked diagrams through third order in perturbation theory. Discrepancies for the mass dependence of the effective interaction for several JT configurations with respect to empirically deduced mass dependencies is reported. The role of core polarization processes through third order were found to be one of the mechanisms behind these discrepancies. Compared to the results obtained with the Paris potential, more attraction is introduced by the Bonn potential for all matrix elements of concerns, a result which agrees well with previous findings for the particle-particle interaction in the same mass regions. A qualitative agreements with experimental data is obtained. 31 refs., 6 figs., 8 tabs

  3. High Valence, Normal Valence and Unknown Valence

    DEFF Research Database (Denmark)

    Morsing, Thorbjørn Juul

    Because of the diverse nature of this thesis, each of the six chapters are briey described individually. Chapter 1 details the synthesis and characterisation of a rare example of a ferromagnetically coupled chromium(III) dimer (Ph4P)4[(SCN)4Cr(OH)2Cr(NCS)4] 2 NCCH3. The compound has been characte......Because of the diverse nature of this thesis, each of the six chapters are briey described individually. Chapter 1 details the synthesis and characterisation of a rare example of a ferromagnetically coupled chromium(III) dimer (Ph4P)4[(SCN)4Cr(OH)2Cr(NCS)4] 2 NCCH3. The compound has been...... the serendipitous synthesis of the nitrido-bridged [Rh(en)3]2- [(CN)5MnNMn(CN)5]. The complex anion have previously been studied in the form of the mixed Rb4Na2-salt. In this earlier study, the nitrido-bridge was found to be asymmetrical with the axial ligands in an eclipsed formation. The complex was...... described as a mixed valence MnII/MnV system. This is not the case for the present system where the bridge is symmetrical, slightly bent and the axial ligands are in a staggered conformation. XANES measurements along with DFT calculations suggest that the Rb4Na2-salt is indeed best described as Mn...

  4. Dynamic force spectroscopy on multiple bonds: experiments and model

    CERN Document Server

    Erdmann, T; Nassoy, P; Schwarz, U S

    2007-01-01

    We probe the dynamic strength of multiple biotin-streptavidin adhesion bonds under linear loading using the biomembrane force probe setup for dynamic force spectroscopy. Measured rupture force histograms are compared to results from a master equation model for the stochastic dynamics of bond rupture under load. This allows us to extract the distribution of the number of initially closed bonds. We also extract the molecular parameters of the adhesion bonds, in good agreement with earlier results from single bond experiments. Our analysis shows that the peaks in the measured histograms are not simple multiples of the single bond values, but follow from a superposition procedure which generates different peak positions.

  5. Bond excitations in the pseudogap phase of the Hubbard Model

    OpenAIRE

    Macridin, Alexandru; Jarrell, Mark (Eds. )

    2008-01-01

    Using the dynamical cluster approximation, we calculate the correlation functions associated with the nearest neighbor bond operator which measure the z component of the spin exchange in the two-dimensional Hubbard model with $U$ equal to the bandwidth. We find that in the pseudogap region, the local bond susceptibility diverges at T=0. This shows the existence of degenerate bond spin excitation and implies quantum criticality and bond order formation when long range correlations are consider...

  6. A dynamical model of the chemical bond

    OpenAIRE

    Hofmann, Holger F.

    1996-01-01

    A new approach to chemical bonding is introduced in order to provide an improved understanding of the connection between basic quantum mechanics and the covalent pair bond. It's focus is on the fact that the energy of the bond is largely given by the kinetic energy of the electrons, while the Coulomb forces are only comparable to the kinetic energy terms close to the atomic nuclei, where they define the shape and the size of the atomic orbitals. If atomic orbitals are used as a starting point...

  7. DSE inspired model for the pion's valence dressed-quark GPD

    CERN Document Server

    Chang, L; Moutarde, H; Roberts, C D; Rodríguez-Quintero, J; Sabatié, F

    2015-01-01

    We sketch here an approach to the computation of generalised parton distributions (GPDs), based upon a rainbow-ladder (RL) truncation of QCD's Dyson-Schwinger equations and exemplified via the pion's valence dressed-quark GPD, $H_\\pi^{\\rm v}(x,\\xi,t)$. Our analysis focuses on the case of zero skewness, $\\xi=0$, and underlines that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for $H_\\pi^{\\rm v}(x,0,t)$, expressed as the Radon transform of a single amplitude. Therewith we obtain results for $H_\\pi^{\\rm v}(x,0,t)$ and the associated impact-parameter dependent distribution, $q_\\pi^{\\rm v}(x,|\\vec{b}_\\perp|)$, which provide a qualitatively sound picture of the pion's dressed-quark structure at an hadronic scale.

  8. Electron transfer within a reaction path model calibrated by constrained DFT calculations: application to mixed-valence organic compounds.

    Science.gov (United States)

    Mangaud, E; de la Lande, A; Meier, C; Desouter-Lecomte, M

    2015-12-14

    The quantum dynamics of electron transfer in mixed-valence organic compounds is investigated using a reaction path model calibrated by constrained density functional theory (cDFT). Constrained DFT is used to define diabatic states relevant for describing the electron transfer, to obtain equilibrium structures for each of these states and to estimate the electronic coupling between them. The harmonic analysis at the diabatic minima yields normal modes forming the dissipative bath coupled to the electronic states. In order to decrease the system-bath coupling, an effective one dimensional vibronic Hamiltonian is constructed by partitioning the modes into a linear reaction path which connects both equilibrium positions and a set of secondary vibrational modes, coupled to this reaction coordinate. Using this vibronic model Hamiltonian, dissipative quantum dynamics is carried out using Redfield theory, based on a spectral density which is determined from the cDFT results. In a first benchmark case, the model is applied to a series of mixed-valence organic compounds formed by two 1,4-dimethoxy-3-methylphenylene fragments linked by an increasing number of phenylene bridges. This allows us to examine the coherent electron transfer in extreme situations leading to a ground adiabatic state with or without a barrier and therefore to the trapping of the charge or to an easy delocalization. PMID:26041466

  9. A statistical model of hydrogen bond networks in liquid alcohols

    Science.gov (United States)

    Sillrén, Per; Bielecki, Johan; Mattsson, Johan; Börjesson, Lars; Matic, Aleksandar

    2012-03-01

    We here present a statistical model of hydrogen bond induced network structures in liquid alcohols. The model generalises the Andersson-Schulz-Flory chain model to allow also for branched structures. Two bonding probabilities are assigned to each hydroxyl group oxygen, where the first is the probability of a lone pair accepting an H-bond and the second is the probability that given this bond also the second lone pair is bonded. The average hydroxyl group cluster size, cluster size distribution, and the number of branches and leaves in the tree-like network clusters are directly determined from these probabilities. The applicability of the model is tested by comparison to cluster size distributions and bonding probabilities obtained from Monte Carlo simulations of the monoalcohols methanol, propanol, butanol, and propylene glycol monomethyl ether, the di-alcohol propylene glycol, and the tri-alcohol glycerol. We find that the tree model can reproduce the cluster size distributions and the bonding probabilities for both mono- and poly-alcohols, showing the branched nature of the OH-clusters in these liquids. Thus, this statistical model is a useful tool to better understand the structure of network forming hydrogen bonded liquids. The model can be applied to experimental data, allowing the topology of the clusters to be determined from such studies.

  10. Pricing for Catastrophe Bonds Based on Expected-value Model

    Directory of Open Access Journals (Sweden)

    Junfei Chen

    2013-02-01

    Full Text Available As the catastrophes cannot be avoided and result in huge economic losses, therefore the compensation issue for catastrophe losses become an important research topic. Catastrophe bonds can effectively disperse the catastrophe risks which mainly undertaken by the government and the insurance companies currently and focus on capital more effectively in broad capital market, therefore to be an ideal catastrophe securities product. This study adopts Expectancy Theory to supplement and improve the pricing of catastrophe bonds based on Value Theory. A model of expected utility is established to determine the conditions of the expected revenue R of catastrophe bonds. The pricing model of the value function is used to get the psychological value of R,U (R-R‾, for catastrophe bonds. Finally, the psychological value is improved by the value according to expected utility and this can more accurately evaluate catastrophe bonds at a reasonable price. This research can provide decision-making for the pricing of catastrophe bonds.

  11. Theoretical Model of Transformation Superlastic Diffusion Bonding for Eutectoid Steel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is mainly described as two-stage process: Ⅰ The interfacial cavity with shape change from diamond to cylinder.Ⅱ The radius of the cylindrical cavity are reduced and eliminated gradually. A new theoretical model is established for the process of transformation superplastic diffusion bonding (TSDB) ...

  12. Upper Secondary Teachers' Knowledge for Teaching Chemical Bonding Models

    Science.gov (United States)

    Bergqvist, Anna; Drechsler, Michal; Chang Rundgren, Shu-Nu

    2016-01-01

    Researchers have shown a growing interest in science teachers' professional knowledge in recent decades. The article focuses on how chemistry teachers impart chemical bonding, one of the most important topics covered in upper secondary school chemistry courses. Chemical bonding is primarily taught using models, which are key for understanding…

  13. Nature of the Xe(VI) -N Bonds in F6 XeNCCH3 and F6 Xe(NCCH3 )2 and the Stereochemical Activity of Their Xenon Valence Electron Lone Pairs.

    Science.gov (United States)

    Haner, Jamie; Matsumoto, Kazuhiko; Mercier, Hélène P A; Schrobilgen, Gary J

    2016-03-24

    The recently reported syntheses and X-ray crystal structures of the highly endothermic compounds F6 XeNCCH3 and F6 Xe(NCCH3 )2 ⋅CH3 CN provide the first, albeit weakly covalent, Xe(VI) -N bonds. The XeF6 unit of F6 XeNCCH3 possesses distorted octahedral (C3v ) symmetry similar to gas-phase XeF6 , whereas the XeF6 unit of F6 Xe(NCCH3 )2 ⋅CH3 CN possesses C2v symmetry. Herein, the natural bond orbital (NBO), atoms in molecules (AIM), electron localization function (ELF), and molecular electrostatic potential surface (MEPS) analyses show that the Xe valence electron lone pairs (VELPs) of both compounds are stereochemically active. The Xe VELPS are diffuse and ineffectively screen their Xe cores so that the Xe VELP positions correspond to the most electrophilic regions of the MEPS, which enables the opposing N VELP of CH3 CN to coordinate to this region. These bonds are predominantly electrostatic in nature and are interpreted as σ-hole interactions. PMID:26918266

  14. Modelling of the Through-air Bonding Process

    Directory of Open Access Journals (Sweden)

    M. Hossain

    2009-06-01

    Full Text Available A computational fluid dynamics (CFD modelling ofthe through-air bonding process of nonwoven fabricproduction is reported in this article. In the throughairprocess, hot air is passed through the fibrous webto heat and melt polymer fibers. Molten polymersubsequently flows to the point of contact betweenany two fibers to produce a bond. Two differentmodelling strategies are adapted to produce acomprehensive understanding of the through-airbonding process. In macroscale modelling, a CFDmodel is developed treating the whole web as aporous media in order to investigate the effect ofprocess parameters. Results reveal that the timerequired to heat and melt the fibers decreases with theincreasing porosity of the web and the velocity of hotair. The CFD modelling technique is then used toanalyze the bonding process at a more fundamentallevel by considering the bonding of individual fibersat microscale. The effects of the fiber diameter,bonding temperature and contact angle between twofibers on the bonding time are investigated. Resultsshow that the time required to bond fibers is weaklyrelated to bonding temperature and fiber diameter.Fiber orientation angle, on the other hand, hassignificant effect on the progression of bondformation.

  15. Bond graph model-based fault diagnosis of hybrid systems

    CERN Document Server

    Borutzky, Wolfgang

    2015-01-01

    This book presents a bond graph model-based approach to fault diagnosis in mechatronic systems appropriately represented by a hybrid model. The book begins by giving a survey of the fundamentals of fault diagnosis and failure prognosis, then recalls state-of-art developments referring to latest publications, and goes on to discuss various bond graph representations of hybrid system models, equations formulation for switched systems, and simulation of their dynamic behavior. The structured text: • focuses on bond graph model-based fault detection and isolation in hybrid systems; • addresses isolation of multiple parametric faults in hybrid systems; • considers system mode identification; • provides a number of elaborated case studies that consider fault scenarios for switched power electronic systems commonly used in a variety of applications; and • indicates that bond graph modelling can also be used for failure prognosis. In order to facilitate the understanding of fault diagnosis and the presented...

  16. Estimating Structural Models of Corporate Bond Prices in Indonesian Corporations

    Directory of Open Access Journals (Sweden)

    Lenny Suardi

    2010-07-01

    Full Text Available This paper applies the maximum likelihood (ML approaches to implementing the structural model of corporate bond, as suggested by Li and Wong (2008, in Indonesian corporations. Two structural models, extended Merton and Longstaff & Schwartz (LS models, are used in determining these prices, yields, yield spreads and probabilities of default. ML estimation is used to determine the volatility of firm value. Since firm value is unobserved variable, Duan (1994 suggested that the first step of ML estimation is to derive the likelihood function for equity as the option on the firm value. The second step is to ind parameters such as the drift and volatility of firm value, that maximizing this function. The firm value itself is extracted by equating the pricing formula to the observed equity prices. Equity, total liabilities, bond prices data and the firm's parameters (firm value, volatility of firm value, and default barrier are substituted to extended Merton and LS bond pricing formula in order to valuate the corporate bond.These models are implemented to a sample of 24 bond prices in Indonesian corporation during period of 2001-2005, based on criteria of Eom, Helwege and Huang (2004. The equity and bond prices data were obtained from Indonesia Stock Exchange for firms that issued equity and provided regular financial statement within this period. The result shows that both models, in average, underestimate the bond prices and overestimate the yields and yield spread.

  17. Parametrization of Stillinger-Weber potential based on valence force field model: application to single-layer MoS2 and black phosphorus

    Science.gov (United States)

    Jiang, Jin-Wu

    2015-08-01

    We propose parametrizing the Stillinger-Weber potential for covalent materials starting from the valence force-field model. All geometrical parameters in the Stillinger-Weber potential are determined analytically according to the equilibrium condition for each individual potential term, while the energy parameters are derived from the valence force-field model. This parametrization approach transfers the accuracy of the valence force field model to the Stillinger-Weber potential. Furthermore, the resulting Stilliinger-Weber potential supports stable molecular dynamics simulations, as each potential term is at an energy-minimum state separately at the equilibrium configuration. We employ this procedure to parametrize Stillinger-Weber potentials for single-layer MoS2 and black phosphorous. The obtained Stillinger-Weber potentials predict an accurate phonon spectrum and mechanical behaviors. We also provide input scripts of these Stillinger-Weber potentials used by publicly available simulation packages including GULP and LAMMPS.

  18. Application of Bond Graph Modeling for Photovoltaic Module Simulation

    Directory of Open Access Journals (Sweden)

    Madi S.

    2016-01-01

    Full Text Available In this paper, photovoltaic generator is represented using the bond-graph methodology. Starting from the equivalent circuit the bond graph and the block diagram of the photovoltaic generator have been derived. Upon applying bond graph elements and rules a mathematical model of the photovoltaic generator is obtained. Simulation results of this obtained model using real recorded data (irradiation and temperature at the Renewable Energies Development Centre in Bouzaréah – Algeria are obtained using MATLAB/SMULINK software. The results have compared with datasheet of the photovoltaic generator for validation purposes.

  19. Minimal model for dynamic bonding in colloidal transient networks

    Science.gov (United States)

    Krinninger, Philip; Fortini, Andrea; Schmidt, Matthias

    2016-04-01

    We investigate a model for colloidal network formation using Brownian dynamics computer simulations. Hysteretic springs establish transient bonds between particles with repulsive cores. If a bonded pair of particles is separated by a cutoff distance, the spring vanishes and reappears only if the two particles contact each other. We present results for the bond lifetime distribution and investigate the properties of the van Hove dynamical two-body correlation function. The model displays crossover from fluidlike dynamics, via transient network formation, to arrested quasistatic network behavior.

  20. Modelling of the Through-air Bonding Process

    OpenAIRE

    Hossain, M.; M. Acar, Ph.D.; Malalasekera, W.

    2009-01-01

    A computational fluid dynamics (CFD) modelling ofthe through-air bonding process of nonwoven fabricproduction is reported in this article. In the throughairprocess, hot air is passed through the fibrous webto heat and melt polymer fibers. Molten polymersubsequently flows to the point of contact betweenany two fibers to produce a bond. Two differentmodelling strategies are adapted to produce acomprehensive understanding of the through-airbonding process. In macroscale modelling, a CFDmodel is ...

  1. Ab initio valence calculations in chemistry

    CERN Document Server

    Cook, D B

    1974-01-01

    Ab Initio Valence Calculations in Chemistry describes the theory and practice of ab initio valence calculations in chemistry and applies the ideas to a specific example, linear BeH2. Topics covered include the Schrödinger equation and the orbital approximation to atomic orbitals; molecular orbital and valence bond methods; practical molecular wave functions; and molecular integrals. Open shell systems, molecular symmetry, and localized descriptions of electronic structure are also discussed. This book is comprised of 13 chapters and begins by introducing the reader to the use of the Schrödinge

  2. Strain gauge bonding technique of strain measurement using bonded resistance in HT-7U superconducting model coil

    International Nuclear Information System (INIS)

    Strain measurement using bonded resistance in HT-7U superconducting model coil goes along under low temperature (4.2 K), the authors choose WK-09-062TZ-120 strain gauge and M-Bond 600 adhesive made by Micro-Measurement INC. of America, then manage bonding technique properly and get satisfactory result

  3. News from the Periodic Table: An Introduction to "Periodicity Symbols, Tables, and Models for Higher-Order Valency and Donor-Acceptor Kinships"

    Science.gov (United States)

    Bent, Henry A.; Weinhold, Frank

    2007-01-01

    The study presents and explains the various periodicity symbols, tables and models for the higher-order valency and donor-acceptor kinships used in chemistry. The described alternative tables are expected to improve the pedagogical consistency of the chemical periodicity patterns with better electronic behavior.

  4. Comment on 'Parametrization of Stillinger-Weber potential based on a valence force field model: application to single-layer MoS2 and black phosphorus'.

    Science.gov (United States)

    Midtvedt, Daniel; Croy, Alexander

    2016-06-10

    We compare the simplified valence-force model for single-layer black phosphorus with the original model and recent ab initio results. Using an analytic approach and numerical calculations we find that the simplified model yields Young's moduli that are smaller compared to the original model and are almost a factor of two smaller than ab initio results. Moreover, the Poisson ratios are an order of magnitude smaller than values found in the literature. PMID:27121075

  5. Bond slip model for the simulation of reinforced concrete structures

    International Nuclear Information System (INIS)

    This paper presents a new finite element approach to model the steel-concrete bond effects. This model proposes to relate steel, represented by truss elements, with the surrounding concrete in the case where the two meshes are not necessary coincident. The theoretical formulation is described and the model is applied on a reinforced concrete tie. A characteristic stress distribution is observed, related to the transfer of bond forces from steel to concrete. The results of this simulation are compared with a computation in which a perfect relation between steel and concrete is supposed. It clearly shows how the introduction of the bond model can improve the description of the cracking process (finite number of cracks). (authors)

  6. Political Culture and Covalent Bonding. A Conceptual Model of Political Culture Change

    Directory of Open Access Journals (Sweden)

    Camelia Florela Voinea

    2015-01-01

    Full Text Available Our class of models aims at explaining the dynamics of political attitude change by means of the dynamic changes in values, beliefs, norms and knowledge with which it is associated. The model constructs a political culture perspective over the relationship between macro and micro levels of a society and polity. The model defines the bonding mechanism as a basic mechanism of the political culture change by taking inspiration from the valence bonding theory in Chemistry, which has inspired the elaboration of the mechanisms and processes underlying the political culture emergence and the political culture control over the relationship between macro-level political entities and the micro-level individual agents. The model introduces operational definitions of the individual agent in political culture terms. The simulation model is used for the study of emergent political culture change phenomena based on individual interactions (emergent or upward causation as well as the ways in which the macro entities and emergent phenomena influence in turn the behaviors of individual agents (downward causation. The model is used in the ongoing research concerning the quality of democracy and political participation of the citizens in the Eastern European societies after the Fall of Berlin Wall. It is particularly aimed at explaining the long-term effect of the communist legacy and of the communist polity concept and organization onto the political mentalities and behaviors of the citizens with respect to democratic institutions and political power. The model has major implications in political socialization, political involvement, political behavior, corruption and polity modeling.

  7. Modelling of spreading process: effect from hydrogen bonds

    Institute of Scientific and Technical Information of China (English)

    Li Xin; Hu Yuan-Zhong; Jiang Lan

    2008-01-01

    Lubricant spreading on solid substrates has drawn considerable attention not only for the microscopic wetting theory but also for the dramatic application in head-disk interface of magnetic storage drive systems. Molecular dynamic simulation based on a coarse-grained bead-spring model has been used to study such a spreading process.The spreading profiles indicate that the hydrogen bonds among lubricant molecules and the hydrogen bonds between lubricant molecules and polar atoms of solid substrates will complicate the spreading process in a tremendous degree.The hydrogen bonds among lubricant molecules will strengthen the lubricant combination intensity, which may hinder most molecules from flowing down to the substrates and diffusing along the substrates. And the hydrogen bonds between lubricant molecules and polar atoms of solid substrates will confine the lubricant molecules around polar atoms, which may hinder the molecules from diffusing along the substrates and cause precursor film to vanish.

  8. Bond graph model for prediction of PWR natural circulation

    International Nuclear Information System (INIS)

    In operation of a Pressurized Water Reactor, natural circulation is an efficient, passive heat transfer mechanism for cooling. It is often employed for heat removal in operational transients, especially in long-term decay-heat removal operation. To simulate the dynamics of natural circulation, a bond graph representation of the PWR primary system and causal manipulation of the field equations has been modeled. The bond graph method calls for establishing the dynamic equations of multiport systems in state-variable form. Using the analogy of circuit elements in electrical networks, a bond graph consists of multiport capacitances, inertances, dissipations, sources of effort and flow, transformers, gyrators, and ideal junction elements. By treating each component in a PWR primary loop as a multiport element in the bond graph, a set of state-space equations representing the thermal/hydraulic responses of the loop is obtained. The state equations are then solved iteratively by using the program DYSIS developed by MIT

  9. Modelling of spreading process: effect from hydrogen bonds

    International Nuclear Information System (INIS)

    Lubricant spreading on solid substrates has drawn considerable attention not only for the microscopic wetting theory but also for the dramatic application in head-disk interface of magnetic storage drive systems. Molecular dynamic simulation based on a coarse-grained bead-spring model has been used to study such a spreading process. The spreading profiles indicate that the hydrogen bonds among lubricant molecules and the hydrogen bonds between lubricant molecules and polar atoms of solid substrates will complicate the spreading process in a tremendous degree. The hydrogen bonds among lubricant molecules will strengthen the lubricant combination intensity, which may hinder most molecules from flowing down to the substrates and diffusing along the substrates. And the hydrogen bonds between lubricant molecules and polar atoms of solid substrates will confine the lubricant molecules around polar atoms, which may hinder the molecules from diffusing along the substrates and cause precursor film to vanish. (condensed matter: structure, mechanical and thermal properties)

  10. Computational Tools To Model Halogen Bonds in Medicinal Chemistry.

    Science.gov (United States)

    Ford, Melissa Coates; Ho, P Shing

    2016-03-10

    The use of halogens in therapeutics dates back to the earliest days of medicine when seaweed was used as a source of iodine to treat goiters. The incorporation of halogens to improve the potency of drugs is now fairly standard in medicinal chemistry. In the past decade, halogens have been recognized as direct participants in defining the affinity of inhibitors through a noncovalent interaction called the halogen bond or X-bond. Incorporating X-bonding into structure-based drug design requires computational models for the anisotropic distribution of charge and the nonspherical shape of halogens, which lead to their highly directional geometries and stabilizing energies. We review here current successes and challenges in developing computational methods to introduce X-bonding into lead compound discovery and optimization during drug development. This fast-growing field will push further development of more accurate and efficient computational tools to accelerate the exploitation of halogens in medicinal chemistry. PMID:26465079

  11. Fuzzy Case-Based Reasoning in Product Style Acquisition Incorporating Valence-Arousal-Based Emotional Cellular Model

    Directory of Open Access Journals (Sweden)

    Fuqian Shi

    2012-01-01

    Full Text Available Emotional cellular (EC, proposed in our previous works, is a kind of semantic cell that contains kernel and shell and the kernel is formalized by a triple- L = , where P denotes a typical set of positive examples relative to word-L, d is a pseudodistance measure on emotional two-dimensional space: valence-arousal, and δ is a probability density function on positive real number field. The basic idea of EC model is to assume that the neighborhood radius of each semantic concept is uncertain, and this uncertainty will be measured by one-dimensional density function δ. In this paper, product form features were evaluated by using ECs and to establish the product style database, fuzzy case based reasoning (FCBR model under a defined similarity measurement based on fuzzy nearest neighbors (FNN incorporating EC was applied to extract product styles. A mathematical formalized inference system for product style was also proposed, and it also includes uncertainty measurement tool emotional cellular. A case study of style acquisition of mobile phones illustrated the effectiveness of the proposed methodology.

  12. Upper Secondary Teachers' Knowledge for Teaching Chemical Bonding Models

    Science.gov (United States)

    Bergqvist, Anna; Drechsler, Michal; Rundgren, Shu-Nu Chang

    2016-01-01

    Researchers have shown a growing interest in science teachers' professional knowledge in recent decades. The article focuses on how chemistry teachers impart chemical bonding, one of the most important topics covered in upper secondary school chemistry courses. Chemical bonding is primarily taught using models, which are key for understanding science. However, many studies have determined that the use of models in science education can contribute to students' difficulties understanding the topic, and that students generally find chemical bonding a challenging topic. The aim of this study is to investigate teachers' knowledge of teaching chemical bonding. The study focuses on three essential components of pedagogical content knowledge (PCK): (1) the students' understanding, (2) representations, and (3) instructional strategies. We analyzed lesson plans about chemical bonding generated by 10 chemistry teachers with whom we also conducted semi-structured interviews about their teaching. Our results revealed that the teachers were generally unaware of how the representations of models they used affected student comprehension. The teachers had trouble specifying students' difficulties in understanding. Moreover, most of the instructional strategies described were generic and insufficient for promoting student understanding. Additionally, the teachers' rationale for choosing a specific representation or activity was seldom directed at addressing students' understanding. Our results indicate that both PCK components require improvement, and suggest that the two components should be connected. Implications for the professional development of pre-service and in-service teachers are discussed.

  13. Electronic structure and bonding in four-coordinate organometallic complexes of aluminum. Valence photoelectron spectra of BHT-H, Me sub 3 Al(PMe sub 3 ), and Me sub 2 (BHT)Al(PMe sub 3 )

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenberger, D.L.; Hogan, R.H. (Univ. of Arizona, Tucson (USA)); Healy, M.D.; Barron, A.R. (Harvard univ., Cambridge, MA (USA))

    1990-04-25

    The He I valence photoelectron spectra of the Lewis acid-base adducts Me{sub 3}Al(PMe{sub 3}) and Me{sub 2}(BHT)Al(PMe{sub 3}) (BHT{minus}H = 2,6-di-tert-butyl-4-methylphenol) have been obtained to characterize the electronic structure and bonding in four-coordinate organometallic complexes of aluminum. To aid in the assignment of the spectrum of Me{sub 2}(BHT)Al(PMe{sub 3}), the spectrum of the free alcohol, BHT-H, was also obtained. The first and second ionizations of the free BHT-H alcohol show vibrational progressions associated with the symmetric C-C phenyl ring stretching modes, consistent with the b{sub 1} and a{sub 2} {pi} ionizations, respectively, of monosubstituted phenyl rings. In the photoelectron spectrum of BHT coordinated to aluminum in Me{sub 2}(BHT)Al(PMe{sub 3}), the corresponding phenoxide a{sub 2} ionization retains the vibrational structure, but the individual vibrational components are lost in the ionization that corresponds most closely with the b{sub 1}. The loss of vibrational fine structure associated with ionization from the phenyl {pi} b{sub 1} orbital in the coordinated phenoxide shows that the phenoxide is involved in a {pi} interaction with the Me{sub 2}Al(PMe{sub 3}) portion of the molecule.

  14. Pairing preferences of the model mono-valence mono-atomic ions investigated by molecular simulation

    International Nuclear Information System (INIS)

    We carried out a series of potential of mean force calculations to study the pairing preferences of a series of model mono-atomic 1:1 ions with evenly varied sizes. The probabilities of forming the contact ion pair (CIP) and the single water separate ion pair (SIP) were presented in the two-dimensional plots with respect to the ion sizes. The pairing preferences reflected in these plots largely agree with the empirical rule of matching ion sizes in the small and big size regions. In the region that the ion sizes are close to the size of the water molecule; however, a significant deviation from this conventional rule is observed. Our further analysis indicated that this deviation originates from the competition between CIP and the water bridging SIP state. The competition is mainly an enthalpy modulated phenomenon in which the existing of the water bridging plays a significant role

  15. Decision-making deficits in patients with chronic schizophrenia: Iowa Gambling Task and Prospect Valence Learning model

    Science.gov (United States)

    Kim, Myung-Sun; Kang, Bit-Na; Lim, Jae Young

    2016-01-01

    Purpose Decision-making is the process of forming preferences for possible options, selecting and executing actions, and evaluating the outcome. This study used the Iowa Gambling Task (IGT) and the Prospect Valence Learning (PVL) model to investigate deficits in risk-reward related decision-making in patients with chronic schizophrenia, and to identify decision-making processes that contribute to poor IGT performance in these patients. Materials and methods Thirty-nine patients with schizophrenia and 31 healthy controls participated. Decision-making was measured by total net score, block net scores, and the total number of cards selected from each deck of the IGT. PVL parameters were estimated with the Markov chain Monte Carlo sampling scheme in OpenBugs and BRugs, its interface to R, and the estimated parameters were analyzed with the Mann–Whitney U-test. Results The schizophrenia group received significantly lower total net scores compared to the control group. In terms of block net scores, an interaction effect of group × block was observed. The block net scores of the schizophrenia group did not differ across the five blocks, whereas those of the control group increased as the blocks progressed. The schizophrenia group obtained significantly lower block net scores in the fourth and fifth blocks of the IGT and selected cards from deck D (advantageous) less frequently than the control group. Additionally, the schizophrenia group had significantly lower values on the utility-shape, loss-aversion, recency, and consistency parameters of the PVL model. Conclusion These results indicate that patients with schizophrenia experience deficits in decision-making, possibly due to failure in learning the expected value of each deck, and incorporating outcome experiences of previous trials into expectancies about options in the present trial. PMID:27175079

  16. Bond Graph Modeling and Simulation of Mechatronic Systems

    DEFF Research Database (Denmark)

    Habib, Tufail; Nielsen, Kjeld; Jørgensen, Kaj Asbjørn

    2012-01-01

    One of the demanding steps in the design and development of Mechatronic systems is to develop the initial model to visualize the response of a system. The Bond Graph (BG) method is a graphical approach for the design of multidomain systems. That is ideal for visualizing the essential characterist......One of the demanding steps in the design and development of Mechatronic systems is to develop the initial model to visualize the response of a system. The Bond Graph (BG) method is a graphical approach for the design of multidomain systems. That is ideal for visualizing the essential...... characteristics of a system. This paper explores the BG method as a modeling approach to develop Mechatronic systems; a case study about the Radar Antenna pedestal drive system is comprehensively addressed. Flow of energy between different functional elements of the system and their causalities are analyzed...

  17. Indifference of Defaultable Bonds with Stochastic Intensity models

    OpenAIRE

    Regis Houssou; Olivier Besson

    2010-01-01

    The utility-based pricing of defaultable bonds in the case of stochastic intensity models of default risk is discussed. The Hamilton-Jacobi- Bellman (HJB) equations for the value functions is derived. A finite difference method is used to solve this problem. The yield-spreads for both buyer and seller are extracted. The behaviour of the spread curve given the default intensity is analyzed. Finally the impacts of the risk aversion and the correlation coefficient are discussed.

  18. Confining Bond Rearrangement in the Random Center Vortex Model

    CERN Document Server

    Altarawneh, Derar; Engelhardt, Michael

    2015-01-01

    We present static meson-meson and baryon--anti-baryon potentials in Z(2) and Z(3) random center vortex models for the infrared sector of Yang-Mills theory, i.e., hypercubic lattice models of random vortex world-surfaces. In particular, we calculate Polyakov loop correlators of two static mesons resp. (anti-)baryons in a center vortex background and observe that their expectation values follow the minimal area law and show bond rearrangement behavior. The static meson-meson and baryon--anti-baryon potentials are compared with theoretical predictions and lattice QCD simulations.

  19. Confining bond rearrangement in the random center vortex model

    Science.gov (United States)

    Altarawneh, Derar; Höllwieser, Roman; Engelhardt, Michael

    2016-03-01

    We present static meson-meson and baryon-antibaryon potentials in Z (2 ) and Z (3 ) random center vortex models for the infrared sector of Yang-Mills theory, i.e., hypercubic lattice models of random vortex world surfaces. In particular, we calculate multiple Polyakov loop correlators corresponding to static meson-meson or baryon-antibaryon configurations in a center vortex background and observe that their expectation values follow the minimal area law, displaying bond rearrangement behavior, a characteristic expected for the confining dynamics of the strong interaction. The static meson-meson and baryon-antibaryon potentials are compared with theoretical predictions and lattice QCD simulations.

  20. Use of a convenient size-extensive normalization in multi-reference coupled cluster (MRCC) theory with incomplete model space: A novel valence universal MRCC formulation

    International Nuclear Information System (INIS)

    We present in this paper a size-extensive formulation of a valence universal multi-reference coupled cluster (VU-MRCC) theory which uses a general incomplete model space (IMS). The earlier formulations by Mukherjee [D. Mukherjee, Chem. Phys. Lett. 125 (1986) 207] led to size-extensive Heff which was both connected and 'closed', thereby leading to size-extensive energies. However, this necessitated abandoning the intermediate normalization (IN) for the valence universal wave-operator Ω when represented as a normal ordered exponential cluster Ansatz Ω≡{exp(S)} with S as the cluster operator. The lack of IN stemmed from the excitation operator Sq-op which leads to excitations into the complementary model space by their action on at least one model function. The powers of Sq-op can in general bring a model function φi back to another model function φj, and this is the reason why Ω does not respect IN. Sq-op are all labelled by active orbitals only. To achieve connectivity of Heff, it must be a 'closed' operator. A closed operator is one which always produces a model function by its action on another model function. Since the decoupling conditions Lq-op=0, and Lop=0 for the transformed operator L=Ω-1HΩ would be in conflict with Ωq-op=1q-op, the model space projection of Ω, PΩP=P cannot be maintained for the normal ordered Ansatz. This leads to a somewhat awkward expression for Heff. Bera et al. [N. Bera, S. Ghosh, D. Mukherjee, S. Chattopadhyay, J. Phys. Chem. A 109 (2005) 11462] recently tried to simplify the expression for Heff, and accomplished this by introducing suitable counter-terms Xcl in Ω to enforce Ωcl=1cl. We show in this paper that Heff in this formulation leads to a disconnected Heff, though it is equivalent by a similarity transformation to a connected effective hamiltonian H∼eff. Guided by the insight gleaned from this demonstration, we have proposed in this paper a new form of the wave-operator which never generates any powers of Sq

  1. Ising tricriticality in the extended Hubbard model with bond dimerization

    Science.gov (United States)

    Ejima, Satoshi; Essler, Fabian H. L.; Lange, Florian; Fehske, Holger

    2016-06-01

    We explore the quantum phase transition between Peierls and charge-density-wave insulating states in the one-dimensional, half-filled, extended Hubbard model with explicit bond dimerization. We show that the critical line of the continuous Ising transition terminates at a tricritical point, belonging to the universality class of the tricritical Ising model with central charge c =7 /10 . Above this point, the quantum phase transition becomes first order. Employing a numerical matrix-product-state based (infinite) density-matrix renormalization group method we determine the ground-state phase diagram, the spin and two-particle charge excitations gaps, and the entanglement properties of the model with high precision. Performing a bosonization analysis we can derive a field description of the transition region in terms of a triple sine-Gordon model. This allows us to derive field theory predictions for the power-law (exponential) decay of the density-density (spin-spin) and bond-order-wave correlation functions, which are found to be in excellent agreement with our numerical results.

  2. Adsorption mechanism and valency of catechol-functionalized hyperbranched polyglycerols

    Science.gov (United States)

    Krysiak, Stefanie; Wei, Qiang; Rischka, Klaus; Hartwig, Andreas; Haag, Rainer

    2015-01-01

    Summary Nature often serves as a model system for developing new adhesives. In aqueous environments, mussel-inspired adhesives are promising candidates. Understanding the mechanism of the extraordinarily strong adhesive bonds of the catechol group will likely aid in the development of adhesives. With this aim, we study the adhesion of catechol-based adhesives to metal oxides on the molecular level using atomic force microscopy (AFM). The comparison of single catechols (dopamine) with multiple catechols on hyperbranched polyglycerols (hPG) at various pH and dwell times allowed us to further increase our understanding. In particular, we were able to elucidate how to achieve strong bonds of different valency. It was concluded that hyperbranched polyglycerols with added catechol end groups are promising candidates for durable surface coatings. PMID:26150898

  3. Adsorption mechanism and valency of catechol-functionalized hyperbranched polyglycerols

    Directory of Open Access Journals (Sweden)

    Stefanie Krysiak

    2015-05-01

    Full Text Available Nature often serves as a model system for developing new adhesives. In aqueous environments, mussel-inspired adhesives are promising candidates. Understanding the mechanism of the extraordinarily strong adhesive bonds of the catechol group will likely aid in the development of adhesives. With this aim, we study the adhesion of catechol-based adhesives to metal oxides on the molecular level using atomic force microscopy (AFM. The comparison of single catechols (dopamine with multiple catechols on hyperbranched polyglycerols (hPG at various pH and dwell times allowed us to further increase our understanding. In particular, we were able to elucidate how to achieve strong bonds of different valency. It was concluded that hyperbranched polyglycerols with added catechol end groups are promising candidates for durable surface coatings.

  4. THE VALENCE OF CORPUSCULAR PROTEINS.

    Science.gov (United States)

    Gorin, M H; Mover, L S

    1942-07-20

    BY THE USE OF TWO EXTREME MODELS: a hydrated sphere and an unhydrated rod the valence (net charge) of corpuscular proteins can be successfully calculated from electric mobility data by the Debye-Hückel theory (modified to include the effect of the ions in the ion atmosphere) in conjunction with the electrophoretic theory of Henry. As pointed out by Abramson, this permits a comparison with values for the valence from titration data. Electrometric titration measurements of serum albumin B (Kekwick) have been determined at several ionic strengths. These results, together with the available data in the literature for serum albumin B, egg albumin, and beta-lactoglobulin have been used to compare values for the valence calculated from measurements of titration, electrophoresis, and membrane potentials. The results indicate that the usual interpretation of titration curves is open to serious question. By extrapolation of the titration data to zero ionic strength and protein concentration, there results an "intrinsic" net charge curve describing the binding of H(+) (OH(-)) ion alone. This curve agrees closely, in each case, with values of the valence calculated from mobility data (which in turn are in close accord with those estimated from membrane potential measurements). The experimental titration curves in the presence of appreciable quantities of ions and protein deviate widely from the ideal curve. It is suggested that, under these conditions, binding of undissociated acid (base) leads to erroneous values for the net charge. This binding would not affect the electrophoretic mobility. Values of the net charge obtained by the two extreme models from electrophoretic data are in agreement within 15 to 20 per cent. The agreement between the cylindrical model and the titration data is somewhat better in each case than with the sphere; i.e., this comparison enables a choice to be made between asymmetry and hydration in the interpretation of results from sedimentation and

  5. 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.

  6. Vector-based model of elastic bonds for DEM simulation of solids

    CERN Document Server

    Kuzkin, Vitaly A

    2012-01-01

    A new model for computer simulation of solids, composed of bonded particles, is proposed. Vectors rigidly connected with particles are used for description of deformation of a single bond. The expression for potential energy of the bond and corresponding expressions for forces and moments are proposed. Formulas, connecting parameters of the model with longitudinal, shear, bending and torsional stiffnesses of the bond, are derived. It is shown that the model allows to describe any values of the bond stiffnesses exactly. Two different calibration procedures depending on bond length/thickness ratio are proposed. It is shown that parameters of model can be chosen so that under small deformations the bond is equivalent to either Bernoulli-Euler or Timoshenko rod or short cylinder connecting particles. Simple expressions, connecting parameters of V-model with geometrical and mechanical characteristics of the bond, are derived. Computer simulation of dynamical buckling of the straight discrete rod and discrete half-...

  7. Representation of emotional valence in human brain

    OpenAIRE

    Viinikainen, Mikko

    2012-01-01

    All emotions can be evaluated with fair accuracy on the basis of their position on unpleasantness-pleasantness, or valence, dimension. Valence has been considered to be a linear continuum both on experiential and neural level, ranging from very unpleasant to very pleasant. However, using such a model it is difficult to explain complex emotional states, in which we can simultaneously experience unpleasantness and pleasantness, like during a rollercoaster ride or a horror film. Also experiments...

  8. Mesoscale numerical modeling of plastic bonded explosives under shock loading

    Directory of Open Access Journals (Sweden)

    Shang Hailin

    2015-01-01

    Full Text Available Mesoscale responses of plastic bonded explosives under shock loading are investigated using material point method as implemented in the Uintah Computational Framework. The two-dimensional geometrical model which can approximately reflect the mesoscopic structure of plastic bonded explosives was created based on the Voronoi tessellation. Shock loading for the explosive was performed by a piston moving at a constant velocity. For the purpose of investigating the influence of shock strength on the responses of explosives, two different velocities for the piston were used, 200 m/s and 400 m/s, respectively. The simulation results indicate that under shock loading there forms some stress localizations on the grain boundary of explosive. These stress localizations lead to large plastic deformations, and the plastic strain energy transforms to thermal energy immediately, causing temperature to rise rapidly and form some hot spots on grain boundary areas. The comparison between two different piston velocities shows that with increasing shock strength, the distribution of plastic strain and temperature does not have significant change, but their values increase obviously. Namely, the higher the shock strength is, the higher the hot spot temperature will be.

  9. Mesoscale numerical modeling of plastic bonded explosives under shock loading

    Science.gov (United States)

    Shang, Hailin; Zhao, Feng; Ji, Guangfu; Fu, Hua

    2015-09-01

    Mesoscale responses of plastic bonded explosives under shock loading are investigated using material point method as implemented in the Uintah Computational Framework. The two-dimensional geometrical model which can approximately reflect the mesoscopic structure of plastic bonded explosives was created based on the Voronoi tessellation. Shock loading for the explosive was performed by a piston moving at a constant velocity. For the purpose of investigating the influence of shock strength on the responses of explosives, two different velocities for the piston were used, 200 m/s and 400 m/s, respectively. The simulation results indicate that under shock loading there forms some stress localizations on the grain boundary of explosive. These stress localizations lead to large plastic deformations, and the plastic strain energy transforms to thermal energy immediately, causing temperature to rise rapidly and form some hot spots on grain boundary areas. The comparison between two different piston velocities shows that with increasing shock strength, the distribution of plastic strain and temperature does not have significant change, but their values increase obviously. Namely, the higher the shock strength is, the higher the hot spot temperature will be.

  10. Advances in modeling and design of adhesively bonded systems

    CERN Document Server

    Kumar, S

    2013-01-01

    The book comprehensively charts a way for industry to employ adhesively bonded joints to make systems more efficient and cost-effective Adhesively bonded systems have found applications in a wide spectrum of industries (e.g., aerospace, electronics, construction, ship building, biomedical, etc.) for a variety of purposes. Emerging adhesive materials with improved mechanical properties have allowed adhesion strength approaching that of the bonded materials themselves. Due to advances in adhesive materials and the many potential merits that adhesive bonding offers, adhesive bonding has replac

  11. Optimum valence bond scheme for its applications to the prediction of nano-structures and the study of matter properties∗%价键优选法及其在纳米结构预测与物性研究中的应用*

    Institute of Scientific and Technical Information of China (English)

    高翔; 陈晓波; 黎军; 李家明

    2013-01-01

      本文论述价键优选法作为一种新颖的理论方法在材料结构预测与物性研究中的应用,特别是在低维数纳米结构如团簇与纳米线研究中所展示的优势。价键优选法以原子几何构型和电子云(主要是由费米能级附近的分子轨道组成,即广义前线轨道)空间分布来合理决定纳米结构的稳定构型的选取。本文以硅团簇为例说明价键优选法的特点,以及锂、钠、铍、镁等金属团簇为例说明价键优选法在结构预测与材料物性随尺寸演化规律研究中的应用,以锂离子在MoS纳米线中的吸附为例说明价键优选法在储能材料离子传导研究中的应用,最后总结价键优选法的进一步发展方向。%The optimum valence bond scheme is a new theoretical method in generating the initial geometric configurations in molecular dynamics simulations of cluster systems. We will present the application of such a new method to the prediction of nano-structures and the study of matter properties, especially for the low-dimensional nano-structures, such as clusters and nano wires. The optimum valence bond scheme uses the atomic geometry of structures and the space distribution of the valence electrons (mainly the molecular orbitals near the Fermi levels, i.e., the generalized frontier orbitals) to determine the possible stable geometric configurations of nano-structures. Silicon clusters are used to demonstrate the features of the optimum valence bond scheme. Metallic clusters such as those of lithium, sodium, beryllium and magnesium are used as examples to illustrate the application of the scheme to the prediction of structures and the studies of the evolution of the material properties with the sizes of clusters. We will use the adsorption process of lithium ion and MoS nano wire to illustrate the application of the optimum valence bond scheme in the studies of the ionic conduction mechanism of the energy storage materials. We

  12. Modelling Static and Dynamic FRP-Concrete Bond Behaviour Using a Local Concrete Damage Model

    OpenAIRE

    Li, Xiaoqin; Chen, Jian-Fei; Lu, Yong; Yang, Zhenjun

    2015-01-01

    This paper presents a study on the bond behaviour of FRP-concrete bonded joints under static and dynamic loadings, by developing a meso-scale finite element model using the K&C concrete damage model in LS-DYNA. A significant number of single shear experiments under static pull-off loading were modelled with an extensive parametric study covering key factors in the K&C model, including the crack band width, the compressive fracture energy and the shear dilatation factor. It is demonstr...

  13. Modelling Bonds & Credit Default Swaps using a Structural Model with Contagion

    OpenAIRE

    Helen Haworth; Christoph Reisinger; William Shaw

    2007-01-01

    This paper develops a two-dimensional structural framework for valuing credit default swaps and corporate bonds in the presence of default contagion. Modelling the values of related firms as correlated geometric Brownian motions with exponential default barriers, analytical formulae are obtained for both credit default swap spreads and corporate bond yields. The credit dependence structure is influenced by both a longer-term correlation structure as well as by the possibility of default conta...

  14. Double site-bond percolation model for biomaterial implants

    CERN Document Server

    Mely, H

    2011-01-01

    We present a double site-bond percolation model to account, on the one hand, for the vascularization and/or resorption of biomaterial implant in bones and, on the other hand, for its mechanical continuity. The transformation of the implant into osseous material, and the dynamical formation/destruction of this osseous material is accounted for by creation and destruction of links and sites in two, entangled, networks. We identify the relevant parameters to describe the implant and its evolution, and separate their biological or chemical origin from their physical one. We classify the various phenomena in the two regimes, percolating or non-percolating, of the networks. We present first numerical results in two dimensions.

  15. 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.

  16. Three-dimensional bonded-cell model for grain fragmentation

    Science.gov (United States)

    Cantor, D.; Azéma, E.; Sornay, P.; Radjai, F.

    2016-07-01

    We present a three-dimensional numerical method for the simulation of particle crushing in 3D. This model is capable of producing irregular angular fragments upon particle fragmentation while conserving the total volume. The particle is modeled as a cluster of rigid polyhedral cells generated by a Voronoi tessellation. The cells are bonded along their faces by a cohesive Tresca law with independent tensile and shear strengths and simulated by the contact dynamics method. Using this model, we analyze the mechanical response of a single particle subjected to diametral compression for varying number of cells, their degree of disorder, and intercell tensile and shear strength. In particular, we identify the functional dependence of particle strength on the intercell strengths. We find that two different regimes can be distinguished depending on whether intercell shear strength is below or above its tensile strength. In both regimes, we observe a power-law dependence of particle strength on both intercell strengths but with different exponents. The strong effect of intercell shear strength on the particle strength reflects an interlocking effect between cells. In fact, even at low tensile strength, the particle global strength can still considerably increase with intercell shear strength. We finally show that the Weibull statistics describes well the particle strength variability.

  17. 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...

  18. Learning probabilistic models of hydrogen bond stability from molecular dynamics simulation trajectories

    KAUST Repository

    Chikalov, Igor

    2011-02-15

    Background: Hydrogen bonds (H-bonds) play a key role in both the formation and stabilization of protein structures. They form and break while a protein deforms, for instance during the transition from a non-functional to a functional state. The intrinsic strength of an individual H-bond has been studied from an energetic viewpoint, but energy alone may not be a very good predictor.Methods: This paper describes inductive learning methods to train protein-independent probabilistic models of H-bond stability from molecular dynamics (MD) simulation trajectories of various proteins. The training data contains 32 input attributes (predictors) that describe an H-bond and its local environment in a conformation c and the output attribute is the probability that the H-bond will be present in an arbitrary conformation of this protein achievable from c within a time duration ?. We model dependence of the output variable on the predictors by a regression tree.Results: Several models are built using 6 MD simulation trajectories containing over 4000 distinct H-bonds (millions of occurrences). Experimental results demonstrate that such models can predict H-bond stability quite well. They perform roughly 20% better than models based on H-bond energy alone. In addition, they can accurately identify a large fraction of the least stable H-bonds in a conformation. In most tests, about 80% of the 10% H-bonds predicted as the least stable are actually among the 10% truly least stable. The important attributes identified during the tree construction are consistent with previous findings.Conclusions: We use inductive learning methods to build protein-independent probabilistic models to study H-bond stability, and demonstrate that the models perform better than H-bond energy alone. 2011 Chikalov et al; licensee BioMed Central Ltd.

  19. Modeling and experimental evaluation of the diffusion bonding of the oxide dispersion strengthened steel PM2000

    Science.gov (United States)

    Sittel, Wiebke; Basuki, Widodo W.; Aktaa, Jarir

    2015-10-01

    A modeling based optimization process of the solid state diffusion bonding is presented for joining ferritic oxide dispersion strengthened steels PM2000. An optimization study employing varying bonding temperatures and pressures results in almost the same strength and toughness of the bonded compared to the as received material. TEM investigations of diffusion bonded samples show a homogeneous distribution of oxide particles at the bonding seam similar to that in the bulk. Hence, no loss in strength or creep resistance due to oxide particle agglomeration is found, as verified by the mechanical properties observed for the joint.

  20. Learning Probabilistic Models of Hydrogen Bond Stability from Molecular Dynamics Simulation Trajectories

    KAUST Repository

    Chikalov, Igor

    2011-04-02

    Hydrogen bonds (H-bonds) play a key role in both the formation and stabilization of protein structures. H-bonds involving atoms from residues that are close to each other in the main-chain sequence stabilize secondary structure elements. H-bonds between atoms from distant residues stabilize a protein’s tertiary structure. However, H-bonds greatly vary in stability. They form and break while a protein deforms. For instance, the transition of a protein from a nonfunctional to a functional state may require some H-bonds to break and others to form. The intrinsic strength of an individual H-bond has been studied from an energetic viewpoint, but energy alone may not be a very good predictor. Other local interactions may reinforce (or weaken) an H-bond. This paper describes inductive learning methods to train a protein-independent probabilistic model of H-bond stability from molecular dynamics (MD) simulation trajectories. The training data describes H-bond occurrences at successive times along these trajectories by the values of attributes called predictors. A trained model is constructed in the form of a regression tree in which each non-leaf node is a Boolean test (split) on a predictor. Each occurrence of an H-bond maps to a path in this tree from the root to a leaf node. Its predicted stability is associated with the leaf node. Experimental results demonstrate that such models can predict H-bond stability quite well. In particular, their performance is roughly 20% better than that of models based on H-bond energy alone. In addition, they can accurately identify a large fraction of the least stable H-bonds in a given conformation. The paper discusses several extensions that may yield further improvements.

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

    International Nuclear Information System (INIS)

    For many years, wafer-to-wafer (W2W) direct bonding has been very developed particularly in terms of bonding energy measurement and bonding mechanism comprehension. Nowadays, die-to-wafer (D2W) direct bonding has gained significant attention, for instance, in photonics and microelectro-mechanics, which supposes controlled and reliable fabrication processes. So, whatever the stuck materials may be, it is not obvious whether bonded D2W structures have the same bonding strength as bonded W2W ones, because of possible edge effects of dies. For that reason, it has been strongly required to develop a bonding energy measurement technique which is suitable for D2W structures. In this paper, both D2W- and W2W-type standard SiO2-to-SiO2 direct bonding samples are fabricated from the same full-wafer bonding. Modifications of the four-point flexion test (4PT) technique and applications for measuring D2W direct bonding energies are reported. Thus, the comparison between the modified 4PT and the double-cantilever beam techniques is drawn, also considering possible impacts of the conditions of measures such as the water stress corrosion at the debonding interface and the friction error at the loading contact points. Finally, reliability of a modified technique and a new model established for measuring D2W direct bonding energies is demonstrated

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

    Energy Technology Data Exchange (ETDEWEB)

    Tabata, T., E-mail: toshiyuki.tabata@cea.fr; Sanchez, L.; Fournel, F.; Moriceau, H. [Univ. Grenoble Alpes, F-38000 Grenoble, France and CEA, LETI, MINATEC Campus, F-38054 Grenoble (France)

    2015-07-07

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

  3. CoCo Bonds Valuation with Equity- and Credit-Calibrated First Passage Structural Models

    OpenAIRE

    Damiano Brigo; Jo\\~ao Garcia; Nicola Pede

    2013-01-01

    After the beginning of the credit and liquidity crisis, financial institutions have been considering creating a convertible-bond type contract focusing on Capital. Under the terms of this contract, a bond is converted into equity if the authorities deem the institution to be under-capitalized. This paper discusses this Contingent Capital (or Coco) bond instrument and presents a pricing methodology based on firm value models. The model is calibrated to readily available market data. A stress t...

  4. Meso-scale three-dimensional modeling of bond in FRP-strengthened masonry

    OpenAIRE

    Ghiassi, Bahman; Oliveira, Daniel V.; Lourenço, Paulo B.; Marcari, Giancarlo

    2012-01-01

    Performance of masonry elements externally strengthened with fiber reinforced polymers (FRPs) is intrinsically dependent on the bond behavior between the composite material and masonry substrate. Therefore, a sound understanding of the interface behavior is crucial at the design stage. In this paper, a three-dimensional model based on the smeared crack modeling approach is presented for investigating the bond behavior in FRP-strengthened masonry elements. The threedimensional aspects of bond ...

  5. Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    James A. Smith; Jeffrey M. Lacy; Barry H. Rabin

    2014-07-01

    12. Other advances in QNDE and related topics: Preferred Session Laser-ultrasonics Developing A Laser Shockwave Model For Characterizing Diffusion Bonded Interfaces 41st Annual Review of Progress in Quantitative Nondestructive Evaluation Conference QNDE Conference July 20-25, 2014 Boise Centre 850 West Front Street Boise, Idaho 83702 James A. Smith, Jeffrey M. Lacy, Barry H. Rabin, Idaho National Laboratory, Idaho Falls, ID ABSTRACT: The US National Nuclear Security Agency has a Global Threat Reduction Initiative (GTRI) which is assigned with reducing the worldwide use of high-enriched uranium (HEU). A salient component of that initiative is the conversion of research reactors from HEU to low enriched uranium (LEU) fuels. An innovative fuel is being developed to replace HEU. The new LEU fuel is based on a monolithic fuel made from a U-Mo alloy foil encapsulated in Al-6061 cladding. In order to complete the fuel qualification process, the laser shock technique is being developed to characterize the clad-clad and fuel-clad interface strengths in fresh and irradiated fuel plates. The Laser Shockwave Technique (LST) is being investigated to characterize interface strength in fuel plates. LST is a non-contact method that uses lasers for the generation and detection of large amplitude acoustic waves to characterize interfaces in nuclear fuel plates. However the deposition of laser energy into the containment layer on specimen’s surface is intractably complex. The shock wave energy is inferred from the velocity on the backside and the depth of the impression left on the surface from the high pressure plasma pulse created by the shock laser. To help quantify the stresses and strengths at the interface, a finite element model is being developed and validated by comparing numerical and experimental results for back face velocities and front face depressions with experimental results. This paper will report on initial efforts to develop a finite element model for laser

  6. Organization of atomic bond tensions in model glasses

    OpenAIRE

    Kustanovich, T.; Rabin, Y.; Olami, Z.

    2002-01-01

    In order to understand whether internal stresses in glasses are correlated or randomly distributed, we study the organization of atomic bond tensions (normal forces between pairs of atoms). Measurements of the invariants of the atomic bond tension tensor in simulated 2D and 3D binary Lennard-Jones glasses, reveal new and unexpected correlations and provide support for Alexander's conjecture about the non-random character of internal stresses in amorphous solids.

  7. Numerical Modelling of the Concrete/Rebar Bond

    OpenAIRE

    Phan, Thanh Song; Rossi, Pierre; Tailhan, Jean-Louis

    2015-01-01

    The simulation of the behaviour of the rebar-concrete bond is of primary importance for an accurate description of cracking processes in reinforced concrete structures and an improved prediction of their durability. In this paper, the methodology used to identify the mechanical behaviour of a rebar-concrete bond in the case of a particular steel reinforcement is first mentioned. The methodology consists in simulating the probabilistic mechanical behaviour of RC tie-beams (170 x 10 x 10 cm), s...

  8. Demystifying Introductory Chemistry. Part 2: Bonding and Molecular Geometry Without Orbitals--the Electron Domain Model.

    Science.gov (United States)

    Gillespie, Ronald J.; And Others

    1996-01-01

    Presents an alternative approach to bonding and geometry--the electron domain model--which avoids some of the problems with the conventional approach. Discusses difficulties with the orbital model at the introductory level, electron spin and the Pauli exclusion principle, electron pair domains, nonequivalent domains, multiple bonds, and origins…

  9. Modelling and simulation of power electronic systems using a bond graph formalism

    OpenAIRE

    Araújo, R.; Leite, V; Freitas, D

    2002-01-01

    This paper deals with the modelling of power electronic systems using the bond graph formalism. The switching components are modelled using an ideal representation so that a constant topology system is obtained. The purpose of the present contribution is to discuss a technique that combines bond graph energy-flow modelling and signal-flow modelling schemes for simulation and prototyping of signal processing algorithms in power electronics systems. In this paper, we will discuss models of the ...

  10. Core and valence thermal vibrations in diamond, silicon, and germanium

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, R. (School of Physics, Madurai Kamaraj Univ. (India)); Balamurugan, P. (School of Physics, Madurai Kamaraj Univ. (India)); Mohanlal, S.K. (School of Physics, Madurai Kamaraj Univ. (India))

    1994-08-01

    An analysis is made using published X-ray data, for the thermal vibrations in diamond, silicon, and germanium. The overall thermal vibration is split into core and valence contributions, because valence electrons can oscillate with different phase and amplitude than core electrons due to bond polarizability. Using indigenously developed computer programs the published data are analyzed. In the first phase, the overall Debye-Waller factor of diamond, Si, and Ge together with scaling and extinction factors are refined using the method of least squares. In the second phase, the core and valence contributions of the harmonic temperature factor are evaluated. Finally, in the third phase, the core and valence contributions of the anharmonic temperature factor are evaluated. The error in the fitting procedure is less than 1% for Si and Ge and about 3% for diamond. (orig.)

  11. Strong disorder fixed points in the two-dimensional random-bond Ising model

    OpenAIRE

    Picco, Marco; Honecker, Andreas; Pujol, Pierre

    2006-01-01

    The random-bond Ising model on the square lattice has several disordered critical points, depending on the probability distribution of the bonds. There are a finite-temperature multicritical point, called Nishimori point, and a zero-temperature fixed point, for both a binary distribution where the coupling constants take the values +/- J and a Gaussian disorder distribution. Inclusion of dilution in the +/- J distribution (J=0 for some bonds) gives rise to another zero-temperature fixed point...

  12. Comment on ‘Parametrization of Stillinger–Weber potential based on a valence force field model: application to single-layer MoS2 and black phosphorus’

    Science.gov (United States)

    Midtvedt, Daniel; Croy, Alexander

    2016-06-01

    We compare the simplified valence-force model for single-layer black phosphorus with the original model and recent ab initio results. Using an analytic approach and numerical calculations we find that the simplified model yields Young's moduli that are smaller compared to the original model and are almost a factor of two smaller than ab initio results. Moreover, the Poisson ratios are an order of magnitude smaller than values found in the literature.

  13. The Mechanism of Covalent Bonding: Analysis within the Huckel Model of Electronic Structure

    Science.gov (United States)

    Nordholm, Sture; Back, Andreas; Backsay, George B.

    2007-01-01

    The commonly used Huckel model of electronic structure is employed to study the mechanisms of covalent bonding, a quantum effect related to electron dynamics. The model also explains the conjugation and aromaticity of planar hydrocarbon molecules completely.

  14. Modelling the Loss of Steel-Concrete Bonds in Corroded Reinforced Concrete Beams

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    The existing stochastic models for deterioration of reinforced concrete structures is extended by adding modelling of "loss of bond" due to corrosion between the reinforcement bars and the surrounding concrete....

  15. Effect of the W addition content on valence electron structure and properties of MoSi2-based solid solution alloys

    International Nuclear Information System (INIS)

    Highlights: → Based on the EET, the valence electron structures of MoSi2-based solid solution alloys have been analyzed using the average atom model. → Analysis of the valence electron structure and mechanical properties relationship. → The results of theoretic calculation have been verified by the experimental results. - Abstract: Based on the empirical electron theory (EET) of solids and molecules, the valence electron structures (VES) of MoSi2-based solid solution alloys have been analyzed using the average atom model. The results showed that with the increase of the W addition content, the hybridization steps of Mo and Si atom of the alloys occurred in C3 and 1, respectively. The hybridization step of W was always C5. The bond energy of the main bond branch, the covalence electron number on the strongest bond and the percentage of the total covalent electron numbers accounting for the total valence electron number of (Mo1-x, Wx)Si2 solid solutions increased with the increase of W addition content. These suggested that the addition of W would increase the melting point, hardness and strength and decrease the fracture toughness of (Mo1-x, Wx)Si2 solid solutions. Based on those results, MoSi2-based solid solution alloys were manufactured, and the results of the experiments were in accordance with those of the theory.

  16. Softening of Phase Transition in 2D Potts Model Under Quenched Bond Randomness

    OpenAIRE

    Yaşar, Fatih; Gündüç, Yiğit; Çelik, Tarık

    1997-01-01

    We have simulated, by using cluster algorithm, the $q=8$ state Potts model in two-dimension with varying amount of quenched bond randomness. We have shown that there exist a finite size dependent threshold value of the introduced quenched bond randomness for rounding the first-order phase transition and this threshold value becomes smaller as the system size increased.

  17. Analysis, Modeling and Simulation of Mechatronic Systems using the Bond Graph Method

    Directory of Open Access Journals (Sweden)

    A. Alabakhshizadeh

    2011-01-01

    Full Text Available The Bond Graph is the proper choice of physical system used for: (i Modeling which can be applied to systems combining multidisciplinary energy domains, (ii Analysis to provide a great value proposition for finding the algebraic loops within the system enabling the process of troubleshooting and eliminating the defects by using the proper component(s to fix the causality conflict even without being acquainted in the proper system, and (iii Simulation facilitated through derived state space equations from the Bond Graph model is solved using industrial simulation software, such as 20-Sim. The Bond Graph technique is a graphical language of modeling, in which component energy ports are connected by bonds that specify the transfer of energy between system components. Following a brief introduction of the Bond Graph methodology and techniques, two separate case studies are comprehensively addressed. The first case study is a systematic implementation of a fourth order electrical system and conversion to mechanical system while the second case study presents modeling of the Dielectric Electro Active Polymer (DEAP actuator. Building the systematic Bond Graph of multifaceted system and ease of switching between different domains are aims of the first case study while the second study shows how a complex mechatronic system could be analyzed and built by the Bond Graph. The respective Bond Graphs in each case is evaluated in the light of mathematical equations and simulations. Excellent correlation has been achieved between the simulation results and proper system equations.

  18. Indirect consideration of un-bonded tendons in 1/4 PCCV model

    International Nuclear Information System (INIS)

    This paper concentrates on the development of a tendon model which can simulate slip behavior between un-bonded tendons and concrete for finite element modeling of 1/4 PCCV (1:4-scale prestressed concrete containment vessel) model. Differently from the bonded tendon depended on structural section, a stress increase beyond the effective value of initial prestress in the un-bonded tendon is mainly depended on the structural member. Therefore, the tendon stress in the un-bonded tendon can be represented as having uniform distribution along the length of the member if the friction loss is not included. To trace the structural response of prestressed concrete structures, accordingly, a modified stress-strain curve for the un-bonded tendon can be derived through performing the successive iterations. This indirect tendon model can take into account the slip effect between un-bonded tendon and concrete, and then it is incorporated into commercialized programs such as DIANA and ABAQUS which have the fundamental limitation in simulating the un-bonded tendon. Finally, the ultimate pressure capacity analyses of 1/4 PCCV model are carried out to evaluate the efficiency and applicability of this tendon model. The numerical results show that 1/4 PCCV represents the ultimate resisting capacity larger than 3 times of the design pressure. (authors)

  19. Analysis of valence XPS and AES of C, N, O, and F-containing substances by DFT calculations using the model molecules

    International Nuclear Information System (INIS)

    Highlights: • We simulate VXPS and UPS of (Li, C, N, O, F)-containing substances by DFT calculations. • To simulate AES of (Li, C, N, O, F)-atoms with our modified method of the kinetic energy. • We clarify electronic states of (Li, C, N, O, F)-containing substances from simulated results. - Abstract: Experimental valence X-ray photoelectron spectra (VXPS) and Auger electron spectra (AES) of (Li, C, N, O, F) elements of four solid substances [graphite, GaN, SiO2, LiF] are analyzed by density-functional theory calculations using the model molecules of the unit cell. For the calculations, we use deMon density functional theory (DFT) program to estimate VXPS, core-electron binding energies, and (Li, C, N, O, F)-KVV AES of the solid substances. In the AES simulations, we evaluate theoretical kinetic energies of the AES with our modified calculation method. The modified kinetic energies correspond to two final-state holes at the ground state and at the transition-state in DFT calculations, respectively. Experimental KVV AES of the (Li, C, N, O) atoms in the substances agree considerably well to simulation of AES obtained with the maximum kinetic energies of the atoms, while, the experimental F KVV AES of LiF is almost in accordance with the spectra from the transition-state kinetic energy calculations

  20. 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

  1. Automated Modeling and Simulation Using the Bond Graph Method for the Aerospace Industry

    Science.gov (United States)

    Granda, Jose J.; Montgomery, Raymond C.

    2003-01-01

    Bond graph modeling was originally developed in the late 1950s by the late Prof. Henry M. Paynter of M.I.T. Prof. Paynter acted well before his time as the main advantage of his creation, other than the modeling insight that it provides and the ability of effectively dealing with Mechatronics, came into fruition only with the recent advent of modern computer technology and the tools derived as a result of it, including symbolic manipulation, MATLAB, and SIMULINK and the Computer Aided Modeling Program (CAMPG). Thus, only recently have these tools been available allowing one to fully utilize the advantages that the bond graph method has to offer. The purpose of this paper is to help fill the knowledge void concerning its use of bond graphs in the aerospace industry. The paper first presents simple examples to serve as a tutorial on bond graphs for those not familiar with the technique. The reader is given the basic understanding needed to appreciate the applications that follow. After that, several aerospace applications are developed such as modeling of an arresting system for aircraft carrier landings, suspension models used for landing gears and multibody dynamics. The paper presents also an update on NASA's progress in modeling the International Space Station (ISS) using bond graph techniques, and an advanced actuation system utilizing shape memory alloys. The later covers the Mechatronics advantages of the bond graph method, applications that simultaneously involves mechanical, hydraulic, thermal, and electrical subsystem modeling.

  2. Virtual multi-dimensional internal bonds model and its application in simulation of rock mass

    Institute of Scientific and Technical Information of China (English)

    ZHANG ZhenNan; GE XiuRun

    2008-01-01

    VMIB (virtual multi-dimensional internal bonds) is a multiscale mechanical model developed from the VIB (virtual internal bond) theory. In VIB theory, the solid material is considered to consist of random-distributed material particles in microscale. These particles are connected with normal bonds. The macro constitutive relation is derived from the cohesive law between particles. However, in VMIB, the micro particles are connected with both normal and shear bonds. The macro constitutive relation is derived in terms of bond stiffness coefficients. It has been theoretically certified that there exists a corresponding relationship between the two bond stiffness coefficients and the two macro material constants, i.e. the Young's modulus and Poisson ratio. This corresponding relationship suggests that it should be necessary and sufficient to simultaneously account for the normal and shear interactions between particles. Due to the fact that the fracture criterion is directly incorporated into the constitutive relation, both VIB and VMIB present many advantages in simulating fractures of materials. In the damage model of rock mass, a damage tensor is usually defined to describe the distribution of cracks. The damage value in one direction determines the relative stiffness of rock mass in this direction. In VMIB solid, the relative distribution density of micro bonds in one direction determines the relative macro stiffness of the material in this direction. The effects of the damage value and the relative distribution density of bonds are consistent. To simulate the failure behavior of rock mass with VMIB, the presented paper sets up a quantitative relationship between the damage tensor and the relative distribution density of bonds. Comparison of the theoretical and the experimental results shows that VMIB model can represent the effect of distributed cracks on rock mass with this relationship. The presented work provides a foundation for further simulating fracture

  3. A new effective interaction for $0\\hbar\\omega$ shell model calculations in the sdpf valence space

    CERN Document Server

    Nowacki, F

    2007-01-01

    The neutron rich isotopes with Z<20, in particular those with neutron numbers around N=28,have been at the focus of a lot experimental and theoretical scrutiny during the last few years.Shell model calculations using the effective interaction SDPF-NR, were able to predictor to explain most of the properties featured by these nuclei. Prominent among them is the disappearance of the N=28 shell closure for Z<=16. We have incorporated to SDPF-NR some modifications, either on purely theoretical grounds or guided by new experimental information. The proposed interaction, SDPF-U, contains USD as its sd-shell part and KB3G as its pf-shell-part. Its range of applicability is enlarged and its reliability enhanced with respect to the earlier version.

  4. Gradient Bundle Analysis: A Full Topological Approach to Chemical Bonding

    CERN Document Server

    Morgenstern, Amanda

    2016-01-01

    The "chemical bond" is a central concept in molecular sciences, but there is no consensus as to what a bond actually is. Therefore, a variety of bonding models have been developed, each defining the structure of molecules in a different manner with the goal of explaining and predicting chemical properties. This thesis describes the initial development of gradient bundle analysis (GBA), a chemical bonding model that creates a high resolution picture of chemical interactions within the charge density framework. GBA is based on concepts from the quantum theory of atoms in molecules (QTAIM), but uses a more complete picture of the topology and geometry of the electron charge density to understand and predict bonding interactions. Gradient bundles are defined as volumes bounded by zero-flux surfaces (ZFSs) in the gradient of the charge density with well-defined energies. The structure of gradient bundles provides an avenue for detecting the locations of valence electrons, which correspond to reactive regions in a ...

  5. Numerical analysis of linear buckling of wind turbine blade with different trailing bonding models

    Science.gov (United States)

    Zhang, J. D.; Xu, Y.

    2013-12-01

    The work focus on the linear buckling analysis of wind turbine blade with different trailing bonding models. Based on finite element model, it has been demonstrated that there are some differences for buckling load factor between different models. Several different models are valid for buckling analysis.

  6. Theoretical modeling of the catch-slip bond transition in biological adhesion

    Science.gov (United States)

    Gunnerson, Kim; Pereverzev, Yuriy; Prezhdo, Oleg

    2006-05-01

    The mechanism by which leukocytes leave the blood stream and enter inflamed tissue is called extravasation. This process is facilitated by the ability of selectin proteins, produced by the endothelial cells of blood vessels, to form transient bonds with the leukocytes. In the case of P-selectin, the protein bonds with P-selectin glycoprotein ligands (PSGL-1) produced by the leukocyte. Recent atomic force microscopy and flow chamber analyses of the binding of P-selectin to PSGL-1 provide evidence for an unusual biphasic catch-bond/slip-bond behavior in response to the strength of exerted force. This biphasic process is not well-understood. There are several theoretical models for describing this phenomenon. These models use different profiles for potential energy landscapes and how they change under forces. We are exploring these changes using molecular dynamics. We will present a simple theoretical model as well as share some of our early MD results for describing this phenomenon.

  7. Teaching Molecular Geometry with the VSEPR Model

    Science.gov (United States)

    Gillespie, Ronald J.

    2004-01-01

    The first introduction to molecular geometry should be through the simple and easily understood VSEPR model, as the Valence Bond Theory and MO Theory suffer from limitations as far as understanding molecular geometry is concerned. The VSEPR model gives a perfectly satisfactory description of the bonding that follows directly from the Lewis model…

  8. On the relation between hydrogen bonds, tetrahedral order and molecular mobility in model water

    CERN Document Server

    Pereyra, R G; Malaspina, D C; Carignano, M A

    2013-01-01

    We studied by molecular dynamics simulations the relation existing between the lifetime of hydrogen bonds, the tetrahedral order and the diffusion coefficient of model water. We tested four different models: SPC/E, TIP4P-Ew, TIP5P-Ew and Six-site, these last two having sites explicitly resembling the water lone pairs. While all the models perform reasonably well at ambient conditions, their behavior is significantly different for temperatures below 270 K. The models with explicit lone-pairs have a longer hydrogen bond lifetime, a better tetrahedral order and a smaller diffusion coefficient than the models without them.

  9. Probing time-dependent mechanical behaviors of catch bonds based on two-state models

    OpenAIRE

    Xiaofeng Chen; Zhixiu Mao; Bin Chen

    2015-01-01

    With lifetime counter-intuitively being prolonged under forces, catch bonds can play critical roles in various sub-cellular processes. By adopting different “catching” strategies within the framework of two-state models, we construct two types of catch bonds that have a similar force-lifetime profile upon a constant force-clamp load. However, when a single catch bond of either type is subjected to varied forces, we find that they can behave very differently in both force history dependence an...

  10. Determinants of the Government Bond Yield in Spain: A Loanable Funds Model

    Directory of Open Access Journals (Sweden)

    Yu Hsing

    2015-07-01

    Full Text Available This paper applies demand and supply analysis to examine the government bond yield in Spain. The sample ranges from 1999.Q1 to 2014.Q2. The EGARCH model is employed in empirical work. The Spanish government bond yield is positively associated with the government debt/GDP ratio, the short-term Treasury bill rate, the expected inflation rate, the U.S. 10 year government bond yield and a dummy variable representing the debt crisis and negatively affected by the GDP growth rate and the expected nominal effective exchange rate.

  11. Modeling of Covalent Bonding in Solids by Inversion of Cohesive Energy Curves

    CERN Document Server

    Bazant, M Z; Bazant, Martin Z.; Kaxiras, Efthimios

    1996-01-01

    We provide a systematic test of empirical theories of covalent bonding in solids using an exact procedure to invert ab initio cohesive energy curves. By considering multiple structures of the same material, it is possible for the first time to test competing angular functions, expose inconsistencies in the basic assumption of a cluster expansion, and extract general features of covalent bonding. We test our methods on silicon, and provide the direct evidence that the Tersoff-type bond order formalism correctly describes coordination dependence. For bond-bending forces, we obtain skewed angular functions that favor small angles, unlike existing models. As a proof-of-principle demonstration, we derive a Si interatomic potential which exhibits comparable accuracy to existing models.

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

    CERN Document Server

    McKenzie, Ross H

    2014-01-01

    Four diabatic states are used to construct a simple model for double proton transfer in hydrogen bonded complexes. Key parameters in the model are the proton donor-acceptor separation R and the ratio, D_1/D_2, between the proton affinity of a donor with one and two protons. Depending on the values of these two parameters the model describes four qualitatively different ground state potential energy surfaces, having zero, one, two, or four saddle points. In the limit D_2=D_1 the model reduces to two decoupled hydrogen bonds. As R decreases a transition can occur from a concerted to a sequential mechanism for double proton transfer.

  13. A multiscale approach to model hydrogen bonding: The case of polyamide

    Energy Technology Data Exchange (ETDEWEB)

    Gowers, Richard J., E-mail: richard.gowers@manchester.ac.uk; Carbone, Paola, E-mail: paola.carbone@manchester.ac.uk [School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-06-14

    We present a simple multiscale model for polymer chains in which it is possible to selectively remove degrees of freedom. The model integrates all-atom and coarse-grained potentials in a simple and systematic way and allows a fast sampling of the complex conformational energy surface typical of polymers whilst maintaining a realistic description of selected atomistic interactions. In particular, we show that it is possible to simultaneously reproduce the structure of highly directional non-bonded interactions such as hydrogen bonds and efficiently explore the large number of conformations accessible to the polymer chain. We apply the method to a melt of polyamide removing from the model only the degrees of freedom associated to the aliphatic segments and keeping at atomistic resolution the amide groups involved in the formation of the hydrogen bonds. The results show that the multiscale model produces structural properties that are comparable with the fully atomistic model despite being five times faster to simulate.

  14. Valence neutron capture in 54Fe

    International Nuclear Information System (INIS)

    The neutron capture cross section of 54Fe has been measured with 0.2 per cent energy resolution from 2.5 to 500 keV. A large and significant correlation is observed between the s-wave reduced neutron widths and the corresponding total radiative widths. The valence model readily accounts for this correlation as well as a large fraction of the s-wave radiative widths. (author)

  15. Bonding Energy and Growth Habit of Lithium Niobate Single Crystals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    On the basis of crystallographic structure of lithium niobate (LN), the bonding energy was quantitatively calculated by the bond valence sum model, which was employed to investigate the crystal growth. A possible relationship between the crystal growth habit and chemical bonding energy of LN crystals are found. It is found that the higher the bond energy, the slower the growth rate, and the more important the plane. The analytical results indicate that (012) plane is the most influential face for the LN crystal growth, which consists well with the standard card (JCPDS Card: 20-0631) and our previous experimental observation. The current work shows that the chemical bond analysis of LN crystals allows us to predict its growth habit and thus to obtain the expected morphology during the spontaneous growth.

  16. Valence fluctuations between two magnetic configurations

    International Nuclear Information System (INIS)

    The subject of this work is the study of a microscopic model which describes TmSe through its most important feature, i.e.: the valence fluctuations between two magnetic configurations. Chapter I is a general review of the most important physical properties of rare-earth systems with intermediate valence (I.V.) and a general description of experimental results and theoretical models on Tm compounds. In Chapter II the Hamiltonian model is discussed and the loss of rotational invariance is also analyzed. Chapter III is devoted to the study of non-stoichiometric Tsub(x)Se compounds. It is shown that these compounds can be considered as a mixture of TmSe (I.V. system) and Tm3+0.87Se. Chapter IV is devoted to the calculation of spin-and charge susceptibilities. The results obtained permit to explain the essential features of the neutron scattering spectrum in TmSe. In Chapter V, an exactly solvable periodic Hamiltonian is presented. From the experimental results, some fundamental features are deduced to describe TmSe as an intermediate valence system whose two accessible ionic configurations are magnetic (degenerated fundamental state). (M.E.L)

  17. A Multidimensional Measure of Work Valences

    Science.gov (United States)

    Porfeli, Erik J.; Lee, Bora; Weigold, Ingrid K.

    2012-01-01

    Work valence is derived from expectancy-valence theory and the literature on children's vocational development and is presumed to be a general appraisal of work that emerges during the childhood period. Work valence serves to promote and inhibit the motivation and tasks associated with vocational development. A measure of work valence, composed of…

  18. Bond graph modeling and validation of an energy regenerative system for emulsion pump tests.

    Science.gov (United States)

    Li, Yilei; Zhu, Zhencai; Chen, Guoan

    2014-01-01

    The test system for emulsion pump is facing serious challenges due to its huge energy consumption and waste nowadays. To settle this energy issue, a novel energy regenerative system (ERS) for emulsion pump tests is briefly introduced at first. Modeling such an ERS of multienergy domains needs a unified and systematic approach. Bond graph modeling is well suited for this task. The bond graph model of this ERS is developed by first considering the separate components before assembling them together and so is the state-space equation. Both numerical simulation and experiments are carried out to validate the bond graph model of this ERS. Moreover the simulation and experiments results show that this ERS not only satisfies the test requirements, but also could save at least 25% of energy consumption as compared to the original test system, demonstrating that it is a promising method of energy regeneration for emulsion pump tests. PMID:24967428

  19. Bond Graph Modeling and Validation of an Energy Regenerative System for Emulsion Pump Tests

    Directory of Open Access Journals (Sweden)

    Yilei Li

    2014-01-01

    Full Text Available The test system for emulsion pump is facing serious challenges due to its huge energy consumption and waste nowadays. To settle this energy issue, a novel energy regenerative system (ERS for emulsion pump tests is briefly introduced at first. Modeling such an ERS of multienergy domains needs a unified and systematic approach. Bond graph modeling is well suited for this task. The bond graph model of this ERS is developed by first considering the separate components before assembling them together and so is the state-space equation. Both numerical simulation and experiments are carried out to validate the bond graph model of this ERS. Moreover the simulation and experiments results show that this ERS not only satisfies the test requirements, but also could save at least 25% of energy consumption as compared to the original test system, demonstrating that it is a promising method of energy regeneration for emulsion pump tests.

  20. Universality aspects of the d=3 random-bond Blume-Capel model

    OpenAIRE

    Malakis, A.; Berker, A. Nihat; Fytas, N. G.; Papakonstantinou, T.

    2012-01-01

    The effects of bond randomness on the universality aspects of the simple cubic lattice ferromagnetic Blume-Capel model are discussed. The system is studied numerically in both its first- and second-order phase transition regimes by a comprehensive finite-size scaling analysis. We find that our data for the second-order phase transition, emerging under random bonds from the second-order regime of the pure model, are compatible with the universality class of the 3d random Ising model. Furthermo...

  1. Lattice Dynamics of II-VI materials using adiabatic bond charge model

    OpenAIRE

    Rajput, B. D.; Browne, D. A.

    1995-01-01

    We extend the adiabatic bond charge model, originally developed for group IV semiconductors and III-V compounds, to study phonons in more ionic II-VI compounds with a zincblende structure. Phonon spectra, density of states and specific heats are calculated for six II-VI compounds and compared with both experimental data and the results of other models. We show that the 6-parameter bond charge model gives a good description of the lattice dynamics of these materials. We also discuss trends in ...

  2. Cohesive zone modelling of wafer bonding and fracture: effect of patterning and toughness variations

    International Nuclear Information System (INIS)

    Direct wafer bonding has increasingly become popular in the manufacture of microelectromechanical systems and semiconductor microelectronics components. The success of the bonding process is controlled by variables such as wafer flatness and surface preparation. In order to understand the effects of these variables, spontaneous planar crack propagation simulations were performed using the spectral scheme in conjunction with a cohesive zone model. The fracture-toughness on the bond interface is varied to simulate the effect of surface roughness (nanotopography) and patterning. Our analysis indicated that the energetics of crack propagation is sensitive to the local surface property variations. The patterned wafers are tougher (well bonded) than the unpatterned ones of the same average fracture-toughness

  3. Janus Nematic Colloids with Designable Valence

    Directory of Open Access Journals (Sweden)

    Simon Čopar

    2014-05-01

    Full Text Available Generalized Janus nematic colloids based on various morphologies of particle surface patches imposing homeotropic and planar surface anchoring are demonstrated. By using mesoscopic numerical modeling, multiple types of Janus particles are explored, demonstrating a variety of novel complex colloidal structures. We also show binding of Janus particles to a fixed Janus post in the nematic cell, which acts as a seed and a micro-anchor for the colloidal structure. Janus colloidal structures reveal diverse topological defect configurations, which are effectively combinations of surface boojum and bulk defects. Topological analysis is applied to defects, importantly showing that topological charge is not a well determined topological invariant in such patchy nematic Janus colloids. Finally, this work demonstrates colloidal structures with designable valence, which could allow for targeted and valence-conditioned self-assembly at micro- and nano-scale.

  4. Reactions of a sulfonamide antimicrobial with model humic constituents: assessing pathways and stability of covalent bonding.

    Science.gov (United States)

    Gulkowska, Anna; Krauss, Martin; Rentsch, Daniel; Hollender, Juliane

    2012-02-21

    The mechanism of covalent bond formation of the model sulfonamide sulfathiazole (STZ) and the stronger nucleophile para-ethoxyaniline was studied in reactions with model humic acid constituents (quinones and other carbonyl compounds) in the absence and presence of laccase. As revealed by high resolution mass spectrometry, the initial bonding of STZ occurred by 1,2- and 1,4-nucleophilic additions of the aromatic amino group to quinones resulting in imine and anilinoquinone formation, respectively. Experiments using the radical scavenger tert-butyl-alcohol provided the same products and similar formation rates as those without scavenger indicating that probably not radical coupling reactions were responsible for the initial covalent bond formation. No addition with nonquinone carbonyl compounds occurred within 76 days except for a slow 1,4-addition to the β-unsaturated carbonyl 1-penten-3-one. The stability of covalent bonds against desorption and pressurized liquid extraction (PLE) was assessed. The recovery rates showed no systematic differences in STZ extractability between the two product types. This suggests that the strength of bonding is not controlled by the initial type of bond, but by the extent of subsequent incorporation of the reaction product into the formed polymer. This incorporation was monitored for (15)N aniline by (1)H-(15)N HMBC NMR spectroscopy. The initial 1,2- and 1,4-addition bonds were replaced by stronger heterocyclic forms with increasing incubation time. These processes could also hold true for soils, and a slow nonextractable residue formation with time could be related to a slow increase of the amount of covalently bound sulfonamide and the strength of bonding. PMID:22260423

  5. Parental Bonds, Attachment Anxiety, Media Susceptibility, and Body Dissatisfaction: A Mediation Model

    Science.gov (United States)

    Patton, Sarah C.; Beaujean, A. Alexander; Benedict, Helen E.

    2014-01-01

    The developmental trajectory of body image dissatisfaction is unclear. Researchers have investigated sociocultural and developmental risk factors; however, the literature needs an integrative etiological model. In 2009, Cheng and Mallinckrodt proposed a dual mediation model, positing that poor-quality parental bonds, via the mechanisms of…

  6. Pseudo-Bond Graph model for the analysis of the thermal behavior of buildings

    Directory of Open Access Journals (Sweden)

    Merabtine Abdelatif

    2013-01-01

    Full Text Available In this work, a simplified graphical modeling tool, which in some extent can be considered in halfway between detailed physical and Data driven dynamic models, has been developed. This model is based on Bond Graphs approach. This approach has the potential to display explicitly the nature of power in a building system, such as a phenomenon of storage, processing and dissipating energy such as Heating, Ventilation and Air-Conditioning (HVAC systems. This paper represents the developed models of the two transient heat conduction problems corresponding to the most practical cases in building envelope, such as the heat transfer through vertical walls, roofs and slabs. The validation procedure consists of comparing the results obtained with this model with analytical solution. It has shown very good agreement between measured data and Bond Graphs model simulation. The Bond Graphs technique is then used to model the building dynamic thermal behavior over a single zone building structure and compared with a set of experimental data. An evaluation of indoor temperature was carried out in order to check our Bond Graphs model.

  7. DNA Self-Assembly and Computation Studied with a Coarse-grained Dynamic Bonded Model

    DEFF Research Database (Denmark)

    Svaneborg, Carsten; Fellermann, Harold; Rasmussen, Steen

    2012-01-01

    We utilize a coarse-grained directional dynamic bonding DNA model [C. Svaneborg, Comp. Phys. Comm. (In Press DOI:10.1016/j.cpc.2012.03.005)] to study DNA self-assembly and DNA computation. In our DNA model, a single nucleotide is represented by a single interaction site, and complementary sites can...

  8. Learners' Mental Models of Metallic Bonding: A Cross-Age Study

    Science.gov (United States)

    Coll, Richard K.; Treagust, David F.

    2003-01-01

    Mental models of metallic bonding held by learners from three academic levels, secondary school (year 12), undergraduate, and postgraduate, were probed using semistructured interviews including the use of Interviews-About-Events focus cards depicting metallic properties and cards containing depictions of models from curriculum material. The…

  9. Moving beyond Definitions: What Student-Generated Models Reveal about Their Understanding of Covalent Bonding and Ionic Bonding

    Science.gov (United States)

    Luxford, Cynthia J.; Bretz, Stacey Lowery

    2013-01-01

    Chemistry students encounter a variety of terms, definitions, and classification schemes that many instructors expect students to memorize and be able to use. This research investigated students' descriptions of ionic and covalent bonding beyond definitions in order to explore students' knowledge about chemical bonding. Using Johnstone's Multiple…

  10. Thermal-hydraulic modeling and analysis of hydraulic system by pseudo-bond graph

    Institute of Scientific and Technical Information of China (English)

    胡均平; 李科军

    2015-01-01

    To increase the efficiency and reliability of the thermodynamics analysis of the hydraulic system, the method based on pseudo-bond graph is introduced. According to the working mechanism of hydraulic components, they can be separated into two categories: capacitive components and resistive components. Then, the thermal-hydraulic pseudo-bond graphs of capacitive C element and resistance R element were developed, based on the conservation of mass and energy. Subsequently, the connection rule for the pseudo-bond graph elements and the method to construct the complete thermal-hydraulic system model were proposed. On the basis of heat transfer analysis of a typical hydraulic circuit containing a piston pump, the lumped parameter mathematical model of the system was given. The good agreement between the simulation results and experimental data demonstrates the validity of the modeling method.

  11. Bond slip model in cylindrical reinforced concrete elements confined with stirrups

    Science.gov (United States)

    Coccia, Simona; Di Maggio, Erica; Rinaldi, Zila

    2015-12-01

    An analytical model able to evaluate the bond-slip law of confined reinforced concrete elements is developed and presented in this paper. The model is based on the studies developed by Tepfers and by den Uijl and Bigaj on the thick-walled cylinder model and extended to the case of the presence of transverse reinforcement. The bond strength and the considered failure modes (splitting or pull-out failure) are expressed as a function of the geometrical (concrete cover and transverse reinforcement) and mechanical (concrete strength) parameters of the element. The application of the proposed methodology allows to forecast the failure mode, and equations for the bond-slip law are finally proposed for a range of steel strain lower than the yielding one.

  12. Modeling, Control and Analyze of Multi-Machine Drive Systems using Bond Graph Technique

    Directory of Open Access Journals (Sweden)

    J. Belhadj

    2006-03-01

    Full Text Available In this paper, a system viewpoint method has been investigated to study and analyze complex systems using Bond Graph technique. These systems are multimachine multi-inverter based on Induction Machine (IM, well used in industries like rolling mills, textile, and railway traction. These systems are multi-domains, multi-scales time and present very strong internal and external couplings, with non-linearity characterized by a high model order. The classical study with analytic model is difficult to manipulate and it is limited to some performances. In this study, a “systemic approach” is presented to design these kinds of systems, using an energetic representation based on Bond Graph formalism. Three types of multimachine are studied with their control strategies. The modeling is carried out by Bond Graph and results are discussed to show the performances of this methodology

  13. The solid solutions CeRu1-xPdxSn and CeRh1-xPdxSn. Applicability of the ICF model to determine intermediate cerium valencies by comparison with XANES data

    International Nuclear Information System (INIS)

    Several samples of the solid solutions CeRu1-xPdxSn and CeRh1-xPdxSn have been synthesized by arc-melting and characterized by X-ray powder diffraction. Guinier powder patterns prove that the ZrNiAl-type structure is the dominating one, besides the CeRuSn and TiNiSi type structures. The structures of CeRu0.28Pd0.72Sn (ZrNiAl type, P anti 62m, a = 751.95(3), c = 418.70(2) pm, wR2 = 0.0274, 332 F2 values, 14 variables) and CeRh0.66Pd0.34Sn (ZrNiAl type, P anti 62m, a = 750.26(3), c = 411.59(2) pm, wR2 = 0.0533, 358 F2 values, 14 variables) were refined from single crystal diffractometer data. Magnetic measurements in combination with XANES (X-Ray Absorption Near Edge Structure) clearly proved intermediate cerium valencies for most compounds and revealed the best fitting parameters for those with the ICF model (Interconfiguration fluctuation). The electrical resistivity is also influenced by the substitutions. At low and high valence electron counts (VECs) metallic character is present, while around the VEC of CeRhSn the typical resistivity behavior for valence fluctuating compounds is observed.

  14. Arbitrage-free models of stocks and bonds

    OpenAIRE

    Durham, J. Benson

    2013-01-01

    A small but ambitious literature uses affine arbitrage-free models to estimate jointly U.S. Treasury term premiums and the term structure of equity risk premiums. Within this approach, this paper identifies the parameter restrictions that are consistent with a simple dividend discount model, extends the cross-section to Germany and France, averages across multiple observable-factor and market prices of risk specifications, and considers alternative samples for parameter estimation. The result...

  15. A New Material Model for 2D FE Analysis of Adhesively Bonded Composite Joints

    OpenAIRE

    Zhao, Libin; Wang, Yana; TianLiang QIN; Zhang, Jianyu

    2014-01-01

    Effective and convenient stress analysis techniques play important roles in the analysis and design of adhesively bonded composite joints. A new material model is presented at the level of composite ply according to the orthotropic elastic mechanics theory and plane strain assumption. The model proposed has the potential to reserve nature properties of laminates with ply-to-ply modeling. The equivalent engineering constants in the model are obtained only by the material properties of unidirec...

  16. Model building of disulfide bonds in proteins with known three-dimensional structure.

    Science.gov (United States)

    Hazes, B; Dijkstra, B W

    1988-07-01

    As an aid in the selection of sites in a protein where a disulfide bond might be engineered, a computer program has been developed. The algorithm starts with the generation of C beta positions from the N, C alpha and C atom coordinates available from a three-dimensional model. A first set of residue pairs that might form a disulfide bond is selected on the basis of C beta-C beta distances between residues. Then, for each residue in this set, S gamma positions are generated, which satisfy the requirement that, with ideal values for the C alpha-C beta and C beta-S gamma bond lengths and for the bond angle at C beta, the distance between S gamma of residue 1 and C beta of residue 2 in a pair (determined by the bond angle at S gamma 2) is at, or very close to its ideal value. Usually two acceptable S gamma positions are found for each half cystine, resulting in up to four different conformations for the disulfide bond. Finally, these conformations are subjected to an energy minimization procedure to remove large deviations from ideal geometry and their final energies are calculated. User input determines which final conformations are energetically acceptable. These conformations are written to a file to allow further analysis and e.g. inspection on a computer graphics device. PMID:3244694

  17. Virtual multi-dimensional internal bonds model and its application in simulation of rock mass

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    VMIB (virtual multi-dimensional internal bonds) is a multiscale mechanical model developed from the VIB (virtual internal bond) theory. In VIB theory,the solid mate-rial is considered to consist of random-distributed material particles in microscale. These particles are connected with normal bonds. The macro constitutive relation is derived from the cohesive law between particles. However,in VMIB,the micro particles are connected with both normal and shear bonds. The macro constitutive relation is derived in terms of bond stiffness coefficients. It has been theoretically certified that there exists a corresponding relationship between the two bond stiffness coefficients and the two macro material constants,i.e. the Young’s modulus and Poisson ratio. This corresponding relationship suggests that it should be necessary and sufficient to simultaneously account for the normal and shear interactions between particles. Due to the fact that the fracture criterion is directly incorporated into the constitutive relation,both VIB and VMIB present many advantages in simulating fractures of materials. In the damage model of rock mass,a damage tensor is usually defined to describe the distribution of cracks. The damage value in one direction determines the relative stiffness of rock mass in this direction. In VMIB solid,the relative distribution density of micro bonds in one direction determines the relative macro stiffness of the material in this direction. The effects of the damage value and the relative distribution density of bonds are consistent. To simulate the failure behavior of rock mass with VMIB,the presented paper sets up a quantitative relationship between the damage tensor and the rela-tive distribution density of bonds. Comparison of the theoretical and the experi-mental results shows that VMIB model can represent the effect of distributed cracks on rock mass with this relationship. The presented work provides a founda-tion for further simulating fracture

  18. Electronic structure, stacking energy, partial charge, and hydrogen bonding in four periodic B-DNA models

    Science.gov (United States)

    Poudel, Lokendra; Rulis, Paul; Liang, Lei; Ching, W. Y.

    2014-08-01

    We present a theoretical study of the electronic structure of four periodic B-DNA models labeled (AT)10,(GC)10, (AT)5(GC)5, and (AT-GC)5 where A denotes adenine, T denotes thymine, G denotes guanine, and C denotes cytosine. Each model has ten base pairs with Na counterions to neutralize the negative phosphate group in the backbone. The (AT)5(GC)5 and (AT-GC)5 models contain two and five AT-GC bilayers, respectively. When compared against the average of the two pure models, we estimate the AT-GC bilayer interaction energy to be 19.015 Kcal/mol, which is comparable to the hydrogen bonding energy between base pairs obtained from the literature. Our investigation shows that the stacking of base pairs plays a vital role in the electronic structure, relative stability, bonding, and distribution of partial charges in the DNA models. All four models show a highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) gap ranging from 2.14 to 3.12 eV with HOMO states residing on the PO4 + Na functional group and LUMO states originating from the bases. Our calculation implies that the electrical conductance of a DNA molecule should increase with increased base-pair mixing. Interatomic bonding effects in these models are investigated in detail by analyzing the distributions of the calculated bond order values for every pair of atoms in the four models including hydrogen bonding. The counterions significantly affect the gap width, the conductivity, and the distribution of partial charge on the DNA backbone. We also evaluate quantitatively the surface partial charge density on each functional group of the DNA models.

  19. Forming Beliefs: Why Valence Matters.

    Science.gov (United States)

    Sharot, Tali; Garrett, Neil

    2016-01-01

    One of the most salient attributes of information is valence: whether a piece of news is good or bad. Contrary to classic learning theories, which implicitly assume beliefs are adjusted similarly regardless of valence, we review evidence suggesting that different rules and mechanisms underlie learning from desirable and undesirable information. For self-relevant beliefs this asymmetry generates a positive bias, with significant implications for individuals and society. We discuss the boundaries of this asymmetry, characterize the neural system supporting it, and describe how changes in this circuit are related to individual differences in behavior. PMID:26704856

  20. A Unified Bond Graph Modeling Approach for the Ejection Phase of the Cardiovascular System

    Directory of Open Access Journals (Sweden)

    LUBNA MOIN

    2016-07-01

    Full Text Available In this paper the unified Bond Graph model of the left ventricle ejection phase is presented, simulated and validated. The integro-differential and ordinary differential equations obtained from the bond graph models are simulated using ODE45 (Ordinary Differential Equation Solver on MATLAB and Simulink. The results, thus, obtained are compared with CVS (Cardiovascular System physiological data present in Simbiosys (a software for simulating biological systems and also with the CVS Wiggers diagram of heart cycle. As the cardiac activity is a multi domain process that includes mechanical, hydraulic, chemical and electrical events; therefore, for modeling such systems a unified modeling approach is needed. In this paper the unified Bond Graph model of the left ventricle ejection phase is proposed. The Bond Graph conventionalism approach is a graphical method principally powerful to portray multi-energy systems, as it is formulated on the portrayal of power exchanges. The model takes into account a simplified description of the left ventricle which is close to the medical investigation promoting the apperception and the dialogue between engineers and physiologists.

  1. System Response Analysis and Model Order Reduction, Using Conventional Method, Bond Graph Technique and Genetic Programming

    OpenAIRE

    Shahid Ali; Vali Uddin; Lubna Moin

    2009-01-01

    This research paper basically explores and compares the different modeling and analysis techniques and than it also explores the model order reduction approach and significance. The traditional modeling and simulation techniques for dynamic systems are generally adequate for single-domain systems only, but the Bond Graph technique provides new strategies for reliable solutions of multi-domain system. They are also used for analyzing linear and non linear dynamic production system, artificial ...

  2. A steel-concrete bond model for the simulation of industrial structures

    International Nuclear Information System (INIS)

    Reinforced concrete structures may have to fulfill functions that go beyond their simple mechanical resistance. During the cracking process, stresses are progressively transferred from steel to concrete through the steel-concrete interface. This stress transfer has a direct impact on the crack properties. Taking into account these effects seems thus essential to predict correctly the cracking of reinforced concrete structures. Different models exist to represent the steel-concrete bond behavior. However, these models are rarely compatible with large scale simulations (meshing difficulties, heavy computational cost..). To overcome these difficulties, a perfect relation between steel and concrete (same displacements) is generally considered for structural applications. In this contribution, a new finite element approach is proposed to represent the steel-concrete bond effects in a context adapted for large scale simulations. This thesis is divided in three parts: - the development of a finite element steel-concrete bond model adapted for large scale structural applications. This model takes into account mechanical interactions between concrete and steel reinforcement represented by truss elements. - the characterization of the steel-concrete bond behavior. A model for the bond stress-slip law based on experimental observations (experimental campaign on pull-out test carried out during the thesis and data of literature) is proposed. This model differentiates the case of a pull-out failure and of splitting failure and takes into account the material properties and the geometric characteristics of the structure. - an application of the proposed model on a structural element (beam). A four point bending beam is experimentally tested. This test aims to characterize the crack evolution (in particular the crack opening using the image correlation technique). Experimental results are then compared with numerical simulations taking into account the bond-slip effect between

  3. Measurement and modelling of hydrogen bonding in 1-alkanol plus n-alkane binary mixtures

    DEFF Research Database (Denmark)

    von Solms, Nicolas; Jensen, Lars; Kofod, Jonas L.; Michelsen, Michael Locht; Kontogeorgis, Georgios

    Two equations of state (simplified PC-SAFT and CPA) are used to predict the monomer fraction of 1-alkanols in binary mixtures with n-alkanes. It is found that the choice of parameters and association schemes significantly affects the ability of a model to predict hydrogen bonding in mixtures, eve...

  4. Simulating Ru L3-Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

    Energy Technology Data Exchange (ETDEWEB)

    Kuiken, Benjamin E. Van; Valiev, Marat; Daifuku, Stephanie L.; Bannan, Caitlin; Strader, Matthew L.; Cho, Hana; Huse, Nils; Schoenlein, Robert W.; Govind, Niranjan; Khalil, Munira

    2013-04-26

    Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of RuII and RuIII complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6]4- and RuII polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5MII-CN-RuIII(NH3)5] (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.

  5. Binomial Tree Model for Convertible Bond Pricing within Equity to Credit Risk Framework

    OpenAIRE

    K. Milanov; Kounchev, O.

    2012-01-01

    In the present paper we fill an essential gap in the Convertible Bonds pricing world by deriving a Binary Tree based model for valuation subject to credit risk. This model belongs to the framework known as Equity to Credit Risk. We show that this model converges in continuous time to the model developed by Ayache, Forsyth and Vetzal [2003]. To this end, both forms of credit risk modeling, the so-called reduced (constant intensity of default model for the underlying) and the so-called synthesi...

  6. A broken-bond model for grain boundaries in face-centered cubic metals

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, D. (Materials Science Division, Argonne National Laboratory, Argonne, IL (USA))

    1990-10-01

    The interrelation between the number of nearest-neighbor atomic bonds broken upon formation of a grain boundary in an fcc metal and the related zero-temperature boundary energy is investigated by atomistic simulation. Using both a Lennard--Jones and an embedded-atom-method potential, the structures and energies of symmetrical and asymmetrical tilt and twist boundaries are determined. As in free surfaces, a practically linear relationship between the nearest-neighbor miscoordination per unit area of the grain boundary and the related interface energy is obtained. The so-called random-boundary model, in which the interactions across the interface are assumed to be entirely randomized, is shown to provide a basis for understanding the role of broken bonds in both high-angle grain boundaries and free surfaces, thus naturally permitting the analysis of ideal cleavage-fracture energies. A detailed study of low-angle boundaries shows that only the dislocation cores---but not their strain fields---give rise to broken bonds. The complementarity between the dislocation model of Read and Shockley for low-angle boundaries and a broken-bond model for high-angle boundaries is thus elucidated.

  7. Computational insight into relations between electronic and vibrational polarizabilities within the two-state valence-bond charge-transfer model

    Czech Academy of Sciences Publication Activity Database

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

    2007-01-01

    Roč. 337, 1-3 (2007), s. 77-80. ISSN 0301-0104 Grant ostatní: Polish Committee for Scientific Research and the Ministry of Education , Youth, and Sports of the Czech Republic(PL) CZ25 Institutional research plan: CEZ:AV0Z40500505 Keywords : polarizability * first hyperpolarizability * second hyperpolarizability * nonlinear optical properties Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.805, year: 2007

  8. Homogenised constitutive model coupling damage and de-bonding for reinforced concrete structures under cyclic solicitations

    International Nuclear Information System (INIS)

    A new stress resultant constitutive model for reinforced concrete plates under cyclic solicitations is presented. This model is built by the periodic homogenisation approach using the averaging method and couples damage of concrete and periodic de-bonding between concrete and steel rebar. In one-dimensional situations, we derive a closed-form solution of the local problem useful to verify and set up the plate problem. The one dimensional macroscopic constitutive model involves a limited number of parameters, the sensibility of which is studied. Comparison to experimental results underlines the pertinence of the model by considering internal de-bonding in order to properly represent the mechanical dissipation occurring during cyclic loadings on reinforced concrete panels. (authors)

  9. Discrete-Element bonded-particle Sea Ice model DESIgn, version 1.3a - model description and implementation

    Science.gov (United States)

    Herman, Agnieszka

    2016-04-01

    This paper presents theoretical foundations, numerical implementation and examples of application of the two-dimensional Discrete-Element bonded-particle Sea Ice model - DESIgn. In the model, sea ice is represented as an assemblage of objects of two types: disk-shaped "grains" and semi-elastic bonds connecting them. Grains move on the sea surface under the influence of forces from the atmosphere and the ocean, as well as interactions with surrounding grains through direct contact (Hertzian contact mechanics) and/or through bonds. The model has an experimental option of taking into account quasi-three-dimensional effects related to the space- and time-varying curvature of the sea surface, thus enabling simulation of ice breaking due to stresses resulting from bending moments associated with surface waves. Examples of the model's application to simple sea ice deformation and breaking problems are presented, with an analysis of the influence of the basic model parameters ("microscopic" properties of grains and bonds) on the large-scale response of the modeled material. The model is written as a toolbox suitable for usage with the open-source numerical library LIGGGHTS. The code, together with full technical documentation and example input files, is freely available with this paper and on the Internet.

  10. Discrete-Element bonded particle Sea Ice model DESIgn, version 1.3 – model description and implementation

    Directory of Open Access Journals (Sweden)

    A. Herman

    2015-07-01

    Full Text Available This paper presents theoretical foundations, numerical implementation and examples of application of a two-dimensional Discrete-Element bonded-particle Sea Ice model DESIgn. In the model, sea ice is represented as an assemblage of objects of two types: disk-shaped "grains", and semi-elastic bonds connecting them. Grains move on the sea surface under the influence of forces from the atmosphere and the ocean, as well as interactions with surrounding grains through a direct contact (Hertzian contact mechanics and/or through bonds. The model has an option of taking into account quasi-threedimensional effects related to space- and time-varying curvature of the sea surface, thus enabling simulation of ice breaking due to stresses resulting from bending moments associated with surface waves. Examples of the model's application to simple sea ice deformation and breaking problems are presented, with an analysis of the influence of the basic model parameters ("microscopic" properties of grains and bonds on the large-scale response of the modeled material. The model is written as a toolbox suitable for usage with the open-source numerical library LIGGGHTS. The code, together with a full technical documentation and example input files, is freely available with this paper and on the Internet.

  11. Second-order perturbation corrections to singles and doubles coupled-cluster methods: General theory and application to the valence optimized doubles model

    International Nuclear Information System (INIS)

    We present a general perturbative method for correcting a singles and doubles coupled-cluster energy. The coupled-cluster wave function is used to define a similarity-transformed Hamiltonian, which is partitioned into a zeroth-order part that the reference problem solves exactly plus a first-order perturbation. Standard perturbation theory through second-order provides the leading correction. Applied to the valence optimized doubles (VOD) approximation to the full-valence complete active space self-consistent field method, the second-order correction, which we call (2), captures dynamical correlation effects through external single, double, and semi-internal triple and quadruple substitutions. A factorization approximation reduces the cost of the quadruple substitutions to only sixth order in the size of the molecule. A series of numerical tests are presented showing that VOD(2) is stable and well-behaved provided that the VOD reference is also stable. The second-order correction is also general to standard unwindowed coupled-cluster energies such as the coupled-cluster singles and doubles (CCSD) method itself, and the equations presented here fully define the corresponding CCSD(2) energy. (c) 2000 American Institute of Physics

  12. Analysis of high-temperature thermoelectric properties of p-type CoSb3 within a two-valence-band and two-conduction-band model

    Science.gov (United States)

    Kajikawa, Y.

    2014-05-01

    Experimental data on the thermoelectric properties of p-type CoSb3 reported by Caillat et al. [J. Appl. Phys. 80, 4442 (1996)] have been analyzed, assuming not only a pair of the first valence (v1) and the first conduction (c1) bands but also the second valence (v2) and the second conduction (c2) bands. By taking into account the excitation of carriers into the v2 and the c2 bands, the behavior of the Hall coefficient as well as that of the Seebeck coefficient at high temperatures is well explained. By taking into account the nonparabolicity of the v1 band, the temperature dependence of mobility is well explained with assuming scattering due to acoustic phonons, nonpolar and polar optical phonons, and ionized impurities. Furthermore, various material parameters of CoSb3, such as the band-gap energy, effective masses, and deformation potentials, have been deduced from fitting the calculation to the experimental data on the temperature dependences of the Hall coefficient, the mobility, and the Seebeck coefficient. Among them, the band-gap energy and the effective mass of the v1 band have been corrected from the original values estimated by Caillat et al. In addition, it is shown that the experimental data on the hole-concentration dependences of both the room-temperature Seebeck coefficient and the cyclotron mass are well reproduced by the theoretical calculation using the deduced values for the nonparabolic v1 band.

  13. Valuation for an American Continuous-Installment Put Option on Bond under Vasicek Interest Rate Model

    OpenAIRE

    Guoan Huang; Guohe Deng; Lihong Huang

    2009-01-01

    The valuation for an American continuous-installment put option on zero-coupon bond is considered by Kim's equations under a single factor model of the short-term interest rate, which follows the famous Vasicek model. In term of the price of this option, integral representations of both the optimal stopping and exercise boundaries are derived. A numerical method is used to approximate the optimal stopping and exercise boundaries by quadrature formulas. Numerical results and discussions are pr...

  14. Nishimori point in random-bond Ising and Potts models in 2D

    OpenAIRE

    A. Honecker; Jacobsen, J. L.; Picco, M.; Pujol, P.

    2001-01-01

    We study the universality class of the fixed points of the 2D random bond q-state Potts model by means of numerical transfer matrix methods. In particular, we determine the critical exponents associated with the fixed point on the Nishimori line. Precise measurements show that the universality class of this fixed point is inconsistent with percolation on Potts clusters for q=2, corresponding to the Ising model, and q=3

  15. Canonical term-structure models with observable factors and the dynamics of bond risk premiums

    OpenAIRE

    Marcello Pericoli; Marco Taboga

    2006-01-01

    We study the dynamics of risk premiums on the German bond market, employing no-arbitrage term-structure models with both observable and unobservable state variables, recently popularized by Ang and Piazzesi (2003). We conduct a specification analisys based on a new canonical representation for this class of models. We find that risk premiums display a considerable variability over time, are strongly counter-cyclical and bear no significant relation to inflation.

  16. A non-perturbative approach to the random-bond Ising model

    International Nuclear Information System (INIS)

    We study the N → 0 limit of the O(N) Gross-Neveu model in the framework of the massless form-factor approach. This model is related to the continuum limit of the Ising model with random bonds via the replica method. We discuss how this method may be useful in calculating correlation functions of physical operators. The identification of non-perturbative fixed points of the O(N) Gross-Neveu model is pursued by its mapping to a WZW model. (author). 30 refs, 1 fig

  17. A Non-Perturbative Approach to the Random-Bond Ising Model

    CERN Document Server

    Cabra, D C; Mussardo, G; Pujol, P

    1997-01-01

    We study the N -> 0 limit of the O(N) Gross-Neveu model in the framework of the massless form-factor approach. This model is related to the continuum limit of the Ising model with random bonds via the replica method. We discuss how this method may be useful in calculating correlation functions of physical operators. The identification of non-perturbative fixed points of the O(N) Gross-Neveu model is pursued by its mapping to a WZW model.

  18. Reply to Isgur's comments on valence QCD

    International Nuclear Information System (INIS)

    With the goal of understanding the complexity of QCD and the role of symmetry in dynamics, the authors studied a field theory called Valence QCD (VQCD) in which the Z graphs are forbidden so that the Fock space is limited to the valence quarks. The authors calculated nucleon form factors, matrix elements, and hadron masses both with this theory and with quenched QCD on a set of lattices with the same gauge background. Comparing the results of the lattice calculations in these two theories, the authors drew conclusions regarding the SU(6) valence quark model and chiral symmetry. While recognizing the goal of VQCD, Nathan Isgur disagrees on some of the conclusions the authors have drawn. The foremost objection raised in section 2 is to their suggestion that the major part of the hyperfine splittings in baryons is due to Goldstone boson exchange and not one-gluon-exchange (OGE) interactions. The logic of Isgur's objection is that VQCD yields a spectroscopy vastly different from quenched QCD and therefore the structure of the hadrons (to which hyperfine splittings in a quark model are intimately tied) is also suspect so no definite conclusions are possible. To put this into perspective it should be emphasized at the outset that spectroscopy is only one aspect of hadron physics examined in section 1. The authors have studied the axial and scalar couplings of nucleon in terms of FA/DA and FS/DS, the neutron to proton magnetic moment ratio μn/μp, and various form factors. None of these results reveal any pathologies of hadron structure and turn out to be close to the SU(6) relations, as expected. In fact this is what motivated the study of valence degrees of freedom via VQCD. In section 2 the authors address specific issues related to spectroscopy in VQCD. Isgur also presented more general arguments against the idea of boson exchange as a contributor to hyperfine effects. A cornerstone of his discussion is the unifying aspect of OGE in a quark model picture. The authors

  19. Molecular invariants: atomic group valence

    International Nuclear Information System (INIS)

    Molecular invariants may be deduced in a very compact way through Grassman algebra. In this work, a generalized valence is defined for an atomic group; it reduces to the Known expressions for the case of an atom in a molecule. It is the same of the correlations between the fluctions of the atomic charges qc and qd (C belongs to the group and D does not) around their average values. Numerical results agree with chemical expectation. (author)

  20. Screw-vector bond graphs for kinetic-static modelling and analysis of mechanisms

    International Nuclear Information System (INIS)

    This dissertation deals with the kinetic-static modelling and analysis of spatial mechanisms used in robotics systems. A framework is proposed, which embodies a geometrical and a network approach for kinetic-static modelling. For this purpose we use screw theory and bond graphs. A new form of bond graphs is introduced: the screw-vector bond graph, whose power variables are defined to be wrenches and twists expressed as intrinsic screw-vectors. The mechanism is then identified as a network, whose components are kinematic pairs and whose topology is described by a directed graph. A screw-vector Simple Junction Structure represents the topological constraints. Kinematic pairs are represented by one-port elements, defined by two reciprocal screw-vector spaces. Using dual bases of screw-vectors, a generic decomposition of kinematic pair elements is given. The reduction of kinetic-static models of series and parallel kinematic chains is used in order to derive kinetic-static functional models in geometric form. Thereupon, the computational causality assignment is adapted for the graphical analysis of the mobility and the functioning of spatial mechanisms, based on completely or incompletely specified models. (author)

  1. Renormalisation group calculation of correlation functions for the 2D random bond Ising and Potts models

    CERN Document Server

    Dotsenko, V S; Pujol, P; Dotsenko, Vladimir; Picco, Marco; Pujol, Pierre

    1995-01-01

    We find the cross-over behavior for the spin-spin correlation function for the 2D Ising and 3-states Potts model with random bonds at the critical point. The procedure employed is the renormalisation approach of the perturbation series around the conformal field theories representing the pure models. We obtain a crossover in the amplitude for the correlation function for the Ising model which doesn't change the critical exponent, and a shift in the critical exponent produced by randomness in the case of the Potts model. A comparison with numerical data is discussed briefly.

  2. Theoretical modeling of infrared spectra of the hydrogen and deuterium bond in aspirin crystal

    Science.gov (United States)

    Ghalla, Houcine; Rekik, Najeh; Michta, Anna; Oujia, Brahim; Flakus, Henryk T.

    2010-01-01

    An extended quantum theoretical approach of the ν IR lineshape of cyclic dimers of weakly H-bonded species is proposed. We have extended a previous approach [M.E.-A. Benmalti, P. Blaise, H.T. Flakus, O. Henri-Rousseau, Chem. Phys. 320 (2006) 267] by accounting for the anharmonicity of the slow mode which is described by a "Morse" potential in order to reproduce the polarized infrared spectra of the hydrogen and deuterium bond in acetylsalicylic acid (aspirin) crystals. From comparison of polarized IR spectra of isotopically neat and isotopically diluted aspirin crystals it resulted that centrosymmetric aspirin dimer was the bearer of the crystal main spectral properties. In this approach, the adiabatic approximation is performed for each separate H-bond bridge of the dimer and a strong non-adiabatic correction is introduced into the model via the resonant exchange between the fast mode excited states of the two moieties. Within the strong anharmonic coupling theory, according to which the X-H→⋯Y high-frequency mode is anharmonically coupled to the H-bond bridge, this model incorporated the Davydov coupling between the excited states of the two moieties, the quantum direct and indirect dampings and the anharmonicity for the H-bond bridge. The spectral density is obtained within the linear response theory by Fourier transform of the damped autocorrelation functions. The evaluated spectra are in fairly good agreement with the experimental ones by using a minimum number of independent parameters. The effect of deuteration has been well reproduced by reducing simply the angular frequency of the fast mode and the anharmonic coupling parameter.

  3. A bond graph approach to modeling the anuran vocal production system.

    Science.gov (United States)

    Kime, Nicole M; Ryan, Michael J; Wilson, Preston S

    2013-06-01

    Air-driven vocal production systems such as those found in mammals, birds, and anurans (frogs and toads) combine pneumatic and mechanical elements in species-specific ways to produce a diversity of communication signals. This study uses bond graphs to model a generalized anuran vocal production system. Bond graphs allow an incremental approach to modeling dynamic physical systems involving different domains. Anurans provide an example of how signal diversity results from variation in the structure and behavior of vocal system elements. This paper first proposes a bond graph model of the integrated anuran vocal system as a framework for future study. It then presents a simulated submodel of the anuran sound source that produces sustained oscillations in vocal fold displacement and air flow through the larynx. The modeling approach illustrated here should prove of general applicability to other biological sound production systems, and will allow researchers to study the biomechanics of vocal production as well as the functional congruence and evolution of groups of traits within integrated vocal systems. PMID:23742365

  4. Characterization and Development of General Material Models for use in Modeling Structures Bonded with Ductile Adhesives

    OpenAIRE

    Cassino, Christopher

    2005-01-01

    Structural adhesives are materials that are capable of bearing significant loads in shear, and sometimes tension, over a range of strains and strain rates. Adhesively bonded structures can dissipate large amounts of mechanical energy and can be lighter and more efficient than many bolted or vibration welded parts. The largest barrier to using structural adhesives in more applications is the many challenges engineers are presented with when designing and analyzing adhesively bonded structures....

  5. Optimized resonating valence bond state in square lattice: correlations & excitations

    Directory of Open Access Journals (Sweden)

    Z Nourbakhsh

    2009-09-01

    Full Text Available We consider RVB state as a variational estimate for the ground state of Heisenberg antiferromagnet in square lattice. We present numerical calculation of energy, spin-spin correlation function and spin excitation spectrum. We show, that the quantum flactuations reduce of magnetization respect to Neel order. Our results are in good agreement with other methods such as spin-wave calculation and series expansions.

  6. Orientational bond and Néel order in the two-dimensional ionic Hubbard model

    Science.gov (United States)

    Hafez-Torbati, Mohsen; Uhrig, Götz S.

    2016-05-01

    Unconventional phases often occur where two competing mechanisms compensate. An excellent example is the ionic Hubbard model where the alternating local potential δ , favoring a band insulator (BI), competes with the local repulsion U , favoring a Mott insulator (MI). By continuous unitary transformations we derive effective models in which we study the softening of various excitons. The softening signals the instability towards new phases that we describe on the mean-field level. On increasing U from the BI in two dimensions, we find a bond-ordered phase breaking orientational symmetry due to a d -wave component. Then, antiferromagnetic order appears coexisting with the d -wave bond order. Finally, the d -wave order vanishes and a Néel-type MI persists.

  7. Bayesian Network Based Fault Prognosis via Bond Graph Modeling of High-Speed Railway Traction Device

    Directory of Open Access Journals (Sweden)

    Yunkai Wu

    2015-01-01

    component-level faults accurately for a high-speed railway traction system, a fault prognosis approach via Bayesian network and bond graph modeling techniques is proposed. The inherent structure of a railway traction system is represented by bond graph model, based on which a multilayer Bayesian network is developed for fault propagation analysis and fault prediction. For complete and incomplete data sets, two different parameter learning algorithms such as Bayesian estimation and expectation maximization (EM algorithm are adopted to determine the conditional probability table of the Bayesian network. The proposed prognosis approach using Pearl’s polytree propagation algorithm for joint probability reasoning can predict the failure probabilities of leaf nodes based on the current status of root nodes. Verification results in a high-speed railway traction simulation system can demonstrate the effectiveness of the proposed approach.

  8. Spin-splitting calculation for zincblende semiconductors using an atomic bond-orbital model

    International Nuclear Information System (INIS)

    We develop a 16-band atomic bond-orbital model (16ABOM) to compute the spin splitting induced by bulk inversion asymmetry in zincblende materials. This model is derived from the linear combination of atomic-orbital (LCAO) scheme such that the characteristics of the real atomic orbitals can be preserved to calculate the spin splitting. The Hamiltonian of 16ABOM is based on a similarity transformation performed on the nearest-neighbor LCAO Hamiltonian with a second-order Taylor expansion over k-vector at the Γ point. The spin-splitting energies in bulk zincblende semiconductors, GaAs and InSb, are calculated, and the results agree with the LCAO and first-principles calculations. However, we find that the spin-orbit coupling between bonding and antibonding p-like states, evaluated by the 16ABOM, dominates the spin splitting of the lowest conduction bands in the zincblende materials.

  9. Spin-splitting calculation for zincblende semiconductors using an atomic bond-orbital model

    Science.gov (United States)

    Kao, Hsiu-Fen; Lo, Ikai; Chiang, Jih-Chen; Chen, Chun-Nan; Wang, Wan-Tsang; Hsu, Yu-Chi; Ren, Chung-Yuan; Lee, Meng-En; Wu, Chieh-Lung; Gau, Ming-Hong

    2012-10-01

    We develop a 16-band atomic bond-orbital model (16ABOM) to compute the spin splitting induced by bulk inversion asymmetry in zincblende materials. This model is derived from the linear combination of atomic-orbital (LCAO) scheme such that the characteristics of the real atomic orbitals can be preserved to calculate the spin splitting. The Hamiltonian of 16ABOM is based on a similarity transformation performed on the nearest-neighbor LCAO Hamiltonian with a second-order Taylor expansion over \\vec{k} at the Γ point. The spin-splitting energies in bulk zincblende semiconductors, GaAs and InSb, are calculated, and the results agree with the LCAO and first-principles calculations. However, we find that the spin-orbit coupling between bonding and antibonding p-like states, evaluated by the 16ABOM, dominates the spin splitting of the lowest conduction bands in the zincblende materials.

  10. Nonlinear finite element modeling of concrete deep beams with openings strengthened with externally-bonded composites

    International Nuclear Information System (INIS)

    Highlights: ► A 3D nonlinear FE model is developed of RC deep beams with web openings. ► We used cohesion elements to simulate bond. ► The developed FE model is suitable for analysis of such complex structures. -- Abstract: This paper aims to develop 3D nonlinear finite element (FE) models for reinforced concrete (RC) deep beams containing web openings and strengthened in shear with carbon fiber reinforced polymer (CFRP) composite sheets. The web openings interrupted the natural load path either fully or partially. The FE models adopted realistic materials constitutive laws that account for the nonlinear behavior of materials. In the FE models, solid elements for concrete, multi-layer shell elements for CFRP and link elements for steel reinforcement were used to simulate the physical models. Special interface elements were implemented in the FE models to simulate the interfacial bond behavior between the concrete and CFRP composites. A comparison between the FE results and experimental data published in the literature demonstrated the validity of the computational models in capturing the structural response for both unstrengthened and CFRP-strengthened deep beams with openings. The developed FE models can serve as a numerical platform for performance prediction of RC deep beams with openings strengthened in shear with CFRP composites.

  11. Studies on Electronic Charge of the Hydrogen Bond Proton in Model Molecular Systems

    OpenAIRE

    Henryk Chojnacki

    2003-01-01

    Abstract: The population analysis of the hydrogen bond atoms was analyzed within the different basis sets for model molecular systems for the ground and low-lying excited electronic states. The Mulliken, Lőwdin and Hirshfeld methods were used in our investigations. It has been shown that normally the proton is transferred, however, in some excited electronic states the hydrogen atom displacement might be responsible for the tautomeric interconversion.

  12. The US Economy, the Treasury Bond Market and the Specification of Macro-Finance Models

    OpenAIRE

    Peter Spencer

    2013-01-01

    This paper addresses questions about the structure of the economy and financial markets raised by recent research on the term structure. The work of Duffee (2012) and Joslin, Preibsch and Singleton (2012) suggests that macroeconomic variables affect risk premia rather than bond yields, which are driven by just three factors as in the traditional model. This is consistent with the observation that the real world macro-dynamics appear to be much richer than the risk neutral dynamics underpinnin...

  13. Dynamic Scaling and Universality of the Two-Dimensional Random-Bond Potts Model

    Institute of Scientific and Technical Information of China (English)

    YING He-Ping; BIAN Bao-Jun; JI Da-Ren; Lothar Schiilke

    2001-01-01

    Short-time dynamics and universality are investigated for the random-bond Potts model with a trinary distribu tion of quenched randomness on a two-dimensional triangular lattice. The universal power-law scaling behaviour is applied to estimate the exponents z and β/v. Emphasis is placed on dynamic Monte Carlo evolutions for different multi-disorder amplitudes. Our results indicate that the quenched impurities cause a change of the critical universality.

  14. Market Prices of Risk and Return Predictability in a Joint Stock-Bond Pricing Model

    OpenAIRE

    Harry Mamaysky

    2002-01-01

    This paper examines the related questions, of the time-series behavior of expected returns and of return predictability, within the framework of the stock-bond pricing model proposed in Mamaysky (2002). The key advantage of the model-based approach adopted in this paper is that the quantities of interest (i.e. expected returns, prices of risk, and R2's of forecasting regressions of returns on their true conditional expectations) are directly observable (once the model has been fitted to the d...

  15. A re-evaluation of test data on bond in R/C by means of FEM modeling

    OpenAIRE

    Fernández Ruiz, Miguel; Muttoni, Aurelio; Gambarova, Pietro

    2007-01-01

    The role of various parameters governing bond behavior is investigated in this paper taking advantage of a simple but efficient finite-element model, whose fundamental aspects are briefly recalled. Several well-documented test results on bond are examined in order to clarify the relevance of some aspects of bond phenomenological behavior, and to study a few bond situations where testing has been scarce in the past, as in the case of push-in tests. Parametric studies are performed as well, wit...

  16. A New Material Model for 2D FE Analysis of Adhesively Bonded Composite Joints

    Directory of Open Access Journals (Sweden)

    Libin ZHAO

    2014-12-01

    Full Text Available Effective and convenient stress analysis techniques play important roles in the analysis and design of adhesively bonded composite joints. A new material model is presented at the level of composite ply according to the orthotropic elastic mechanics theory and plane strain assumption. The model proposed has the potential to reserve nature properties of laminates with ply-to-ply modeling. The equivalent engineering constants in the model are obtained only by the material properties of unidirectional composites. Based on commercial FE software ABAQUS, a 2D FE model of a single-lap adhesively bonded joint was established conveniently by using the new model without complex modeling process and much professional knowledge. Stress distributions in adhesive were compared with the numerical results by Tsai and Morton and interlaminar stresses between adhesive and adherents were compared with the results from a detailed 3D FE analysis. Good agreements in both cases verify the validity of the proposed model. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.5960

  17. Nuclear masses and the number of valence nucleons

    International Nuclear Information System (INIS)

    An improved version of the liquid drop model is presented. The addition of two terms, linear and quadratic in the total number of valence nucleons (particles or holes), improves the description of atomic masses, which can be fitted with an r.m.s. error of 1.2 MeV. Predictions are analysed an compared with those of established models

  18. Modeling the vapor-liquid equilibria of polymer-solvent mixtures: Systems with complex hydrogen bonding behavior

    DEFF Research Database (Denmark)

    Tsivintzelis, Ioannis; Kontogeorgis, Georgios

    2009-01-01

    The vapor–liquid equilibria of binary polymer–solvent systems was modeled using the Non-Random Hydrogen Bonding (NRHB) model. Mixtures of poly(ethylene glycol), poly(propylene glycol), poly(vinyl alcohol) and poly(vinyl acetate) with various solvents were investigated, while emphasis was put on...... hydrogen bonding systems, in which functional groups of the polymer chain can self-associate or cross-associate with the solvent molecules. Effort has been made to explicitly account for all hydrogen bonding interactions. The results reveal that the NRHB model offers a flexible approach to account for...

  19. Bond graph modeling and simulation of impact dynamics of an automotive crash

    International Nuclear Information System (INIS)

    With increase in the speeds of automotives, safety has become more and more important aspect of designers to care for. Thus, it is necessary to design the automobile body structure keeping in view all the safety requirements. As a result of the above-mentioned facts, in the recent years, the designers in making automotives more safe, more collision resistant and crash worthy have focused increased attention on designing automotives, which provides greater protection for the drivers and the passengers in case of an accident. Before a new model is launched into the market, a complete collision analysis is carried out to check the damage reduction capabilities and impact protection of automotives in case of an accident. Research in the field of automotive collision and impact analysis is a continuing activity and dedicated groups of engineers are devoting their full time and efforts for this. In this research work, the main attention is focused to provide a detailed knowledge about automotive collision analysis. The objective of this research paper is to develop an understanding of the automotive collision response. For this, we have done a simulation experiment in which, on a railroad, a train car is separated from a train and is moving towards two stationary train cars. By using a bond graph model of the system its state-space equations are found. Then by using software, the simulation is carried out. The bond graph method is a graphical presentation of the power flow using bonds. (author)

  20. Predictive Models for Halogen-bond Basicity of Binding Sites of Polyfunctional Molecules.

    Science.gov (United States)

    Glavatskikh, Marta; Madzhidov, Timur; Solov'ev, Vitaly; Marcou, Gilles; Horvath, Dragos; Graton, Jérôme; Le Questel, Jean-Yves; Varnek, Alexandre

    2016-02-01

    Halogen bonding (XB) strength assesses the ability of an electron-enriched group to be involved in complexes with polarizable electrophilic halogenated or diatomic halogen molecules. Here, we report QSPR models of XB of particular relevance for an efficient screening of large sets of compounds. The basicity is described by pKBI2 , the decimal logarithm of the experimental 1 : 1 (B : I2 ) complexation constant K of organic compounds (B) with diiodine (I2 ) as a reference halogen-bond donor in alkanes at 298 K. Modeling involved ISIDA fragment descriptors, using SVM and MLR methods on a set of 598 organic compounds. Developed models were then challenged to make predictions for an external test set of 11 polyfunctional compounds for which unambiguous assignment of the measured effective complexation constant to specific groups out of the putative acceptor sites is not granted. At this stage, developed models were used to predict pKBI2 of all putative acceptor sites, followed by an estimation of the predicted effective complexation constant using the ChemEqui program. The best consensus models perform well both in cross-validation (root mean squared error RMSE=0.39-0.47 logKBI2 units) and external predictions (RMSE=0.49). The SVM models are implemented on our website (http://infochim.u-strasbg.fr/webserv/VSEngine.html) together with the estimation of their applicability domain and an automatic detection of potential halogen-bond acceptor atoms. PMID:27491792

  1. Exact critical behavior of a random bond two-dimensional Ising model

    International Nuclear Information System (INIS)

    A 2D Ising model in which the bonds K fluctuate randomly about K/sub c/, the critical value of the pure system, is considered. The ensemble average of the square of the two-point function, 0s/sub R/>2>/sub Av/, is shown to decay as (lnR)/sup 1/4/R/sup -1/2/ aat the critical point. This implies that 0s/sub R/>>/sub Av/ is bounded above by (lnR)/sup 1/8/R/sup -1/4/ in disagreement with the exp [-(ln lnR)2] decay law found by Dotsenko and Dotsenko by a different method. On the other hand, the present calculation reproduces their specific-heat singularity C--lnchemical bondlntauchemical bond (tau = K-K/sub c/)

  2. Theory of Valence Transition in BiNiO3

    Science.gov (United States)

    Naka, Makoto; Seo, Hitoshi; Motome, Yukitoshi

    2016-02-01

    Motivated by the colossal negative thermal expansion recently found in BiNiO3 , the valence transition accompanied by the charge transfer between the Bi and Ni sites is theoretically studied. We introduce an effective model for Bi -6 s and Ni -3 d orbitals taking into account the valence skipping of Bi cations, and investigate the ground-state and finite-temperature phase diagrams within the mean-field approximation. We find that the valence transition is caused by commensurate locking of the electron filling in each orbital associated with charge and magnetic orderings, and the critical temperature and the nature of the transitions are strongly affected by the relative energy between the Bi and Ni levels and the effective electron-electron interaction in the Bi sites. The obtained phase diagram well explains the temperature- and pressure-driven valence transitions in BiNiO3 and the systematic variation of valence states for a series of Bi and Pb perovskite oxides.

  3. Postpartum Bonding Disorder: Factor Structure, Validity, Reliability and a Model Comparison of the Postnatal Bonding Questionnaire in Japanese Mothers of Infants

    Directory of Open Access Journals (Sweden)

    Yukiko Ohashi

    2016-08-01

    Full Text Available Negative attitudes of mothers towards their infant is conceptualized as postpartum bonding disorder, which leads to serious health problems in perinatal health care. However, its measurement still remains to be standardized. Our aim was to examine and confirm the psychometric properties of the Postnatal Bonding Questionnaire (PBQ in Japanese mothers. We distributed a set of questionnaires to community mothers and studied 392 mothers who returned the questionnaires at 1 month after childbirth. Our model was compared with three other models derived from previous studies. In a randomly halved sample, an exploratory factor analysis yielded a three-factor structure: Anger and Restrictedness, Lack of Affection, and Rejection and Fear. This factor structure was cross-validated by a confirmatory factor analysis using the other halved sample. The three subscales showed satisfactory internal consistency. The three PBQ subscale scores were correlated with depression and psychological abuse scores. Their test–retest reliability between day 5 and 1 month after childbirth was measured by intraclass correlation coefficients between 0.76 and 0.83. The Akaike Information Criteria of our model was better than the original four-factor model of Brockington. The present study indicates that the PBQ is a reliable and valid measure of bonding difficulties of Japanese mothers with neonates.

  4. The multimedia models for the evaluation of exposure bond to the atmospheric emissions of classified installations

    International Nuclear Information System (INIS)

    Risk assessment and environmental impacts studies are realized to preserve the public health. Today one of the most used approach is the use of an atmospheric dispersion model to assess the risks. The data are then injected in a calculation software of exposure bond to polluted soils, to evaluate the risks of non direct exposure. This report details and evaluates the models corresponding to the need: the methodology for assessing Health Risks associated with multiple pathways of exposure to combustor, human health risk assessment proto col for hazardous waste combustion facilities, EUSES, CALTOX, MEPAS, MEND-TOX, RESRAD, MMSOILS, FRAMES-HWIR, PC-GEMS and TRIM. (A.L.B.)

  5. Characterization and Modeling of the Collision Induced Dissociation Patterns of Deprotonated Glycosphingolipids: Cleavage of the Glycosidic Bond

    Science.gov (United States)

    Rožman, Marko

    2016-01-01

    Glycosphingolipid fragmentation behavior was investigated by combining results from analysis of a series of negative ion tandem mass spectra and molecular modeling. Fragmentation patterns extracted from 75 tandem mass spectra of mainly acidic glycosphingolipid species (gangliosides) suggest prominent cleavage of the glycosidic bonds with retention of the glycosidic oxygen atom by the species formed from the reducing end (B and Y ion formation). Dominant product ions arise from dissociation of sialic acids glycosidic bonds whereas product ions resulting from cleavage of other glycosidic bonds are less abundant. Potential energy surfaces and unimolecular reaction rates of several low-energy fragmentation pathways leading to cleavage of glycosidic bonds were estimated in order to explain observed dissociation patterns. Glycosidic bond cleavage in both neutral (unsubstituted glycosyl group) and acidic glycosphingolipids was the outcome of the charge-directed intramolecular nucleophilic substitution (SN2) mechanism. According to the suggested mechanism, the nucleophile in a form of carboxylate or oxyanion attacks the carbon at position one of the sugar ring, simultaneously breaking the glycosidic bond and yielding an epoxide. For gangliosides, unimolecular reaction rates suggest that dominant product ions related to the cleavage of sialic acid glycosidic bonds are formed via direct dissociation channels. On the other hand, low abundant product ions related to the dissociation of other glycosidic bonds are more likely to be the result of sequential dissociation. Although results from this study mainly contribute to the understanding of glycosphingolipid fragmentation chemistry, some mechanistic findings regarding cleavage of the glycosidic bond may be applicable to other glycoconjugates.

  6. Polymer complexes.. XXXX. Supramolecular assembly on coordination models of mixed-valence-ligand poly[1-acrylamido-2-(2-pyridyl)ethane] complexes

    Science.gov (United States)

    El-Sonbati, A. Z.; El-Bindary, A. A.; Diab, M. A.

    2003-02-01

    The build-up of polymer metallic supramolecules based on homopolymer (1-acrylamido-2-(2-pyridyl)ethane (AEPH)) and ruthenium, rhodium, palladium as well as platinum complexes has been pursued with great interest. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes [( 11)+( 12)] in the paper and in mononuclear polymer complexes ( 1)-( 5) it acts as a neutral bidentate ligand coordinating through the N-pyridine and NH-imino atoms, while in the mixed ligand diamagnetic poly-chelates, which are obtained from the reaction of AEPH with PdX 2 and KPtCl 4 in the presence of N-heterocyclic base consisting of polymer complexes ( 9)+( 10), and in monouclear compounds ( 6)-( 8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds ( 13)+( 14) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. The poly-chelates are of 1:1, 1:2 and 3:2 (metal-homopolymer) stoichiometry and exhibit six coordination. The values of ligand field parameters were calculated. The homopolymer and their polymer complexes have been characterized physicochemically.

  7. On Bond Portfolio Management

    OpenAIRE

    Vladislav Kargin

    2002-01-01

    This paper describes a new method of bond portfolio optimization based on stochastic string models of correlation structure in bond returns. The paper shows how to approximate correlation function of bond returns, compute the optimal portfolio allocation using Wiener-Hopf factorization, and check whether a collection of bonds presents arbitrage opportunities.

  8. Valence band structure of binary chalcogenide vitreous semiconductors by high-resolution XPS

    Energy Technology Data Exchange (ETDEWEB)

    Kozyukhin, S., E-mail: sergkoz@igic.ras.ru [Russian Academy of Science, Institute of General and Inorganic Chemistry (Russian Federation); Golovchak, R. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Kovalskiy, A. [Lehigh University, Department of Materials Science and Engineering (United States); Shpotyuk, O. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Jain, H. [Lehigh University, Department of Materials Science and Engineering (United States)

    2011-04-15

    High-resolution X-ray photoelectron spectroscopy (XPS) is used to study regularities in the formation of valence band electronic structure in binary As{sub x}Se{sub 100-x}, As{sub x}S{sub 100-x}, Ge{sub x}Se{sub 100-x} and Ge{sub x}S{sub 100-x} chalcogenide vitreous semiconductors. It is shown that the highest occupied energetic states in the valence band of these materials are formed by lone pair electrons of chalcogen atoms, which play dominant role in the formation of valence band electronic structure of chalcogen-rich glasses. A well-expressed contribution from chalcogen bonding p electrons and more deep s orbitals are also recorded in the experimental valence band XPS spectra. Compositional dependences of the observed bands are qualitatively analyzed from structural and compositional points of view.

  9. Conduction Mechanism of Valence Change Resistive Switching Memory: A Survey

    Directory of Open Access Journals (Sweden)

    Ee Wah Lim

    2015-09-01

    Full Text Available Resistive switching effect in transition metal oxide (TMO based material is often associated with the valence change mechanism (VCM. Typical modeling of valence change resistive switching memory consists of three closely related phenomena, i.e., conductive filament (CF geometry evolution, conduction mechanism and temperature dynamic evolution. It is widely agreed that the electrochemical reduction-oxidation (redox process and oxygen vacancies migration plays an essential role in the CF forming and rupture process. However, the conduction mechanism of resistive switching memory varies considerably depending on the material used in the dielectric layer and selection of electrodes. Among the popular observations are the Poole-Frenkel emission, Schottky emission, space-charge-limited conduction (SCLC, trap-assisted tunneling (TAT and hopping conduction. In this article, we will conduct a survey on several published valence change resistive switching memories with a particular interest in the I-V characteristic and the corresponding conduction mechanism.

  10. Discrete kink dynamics in hydrogen-bonded chains: The one-component model

    DEFF Research Database (Denmark)

    Karpan, V. M.; Zolotaryuk, Yaroslav; Christiansen, Peter Leth; Zolotaryuk, Alexander

    2002-01-01

    We study topological solitary waves (kinks and antikinks) in a nonlinear one-dimensional Klein-Gordon chain with the on-site potential of a double-Morse type. This chain is used to describe the collective proton dynamics in quasi-one-dimensional networks of hydrogen bonds, where the on-site poten......We study topological solitary waves (kinks and antikinks) in a nonlinear one-dimensional Klein-Gordon chain with the on-site potential of a double-Morse type. This chain is used to describe the collective proton dynamics in quasi-one-dimensional networks of hydrogen bonds, where the on......-site potential plays the role of the proton potential in the hydrogen bond. The system supports a rich variety of stationary kink solutions with different symmetry properties. We study the stability and bifurcation structure of all these stationary kink states. An exactly solvable model with a piecewise...... "parabola-constant" approximation of the double-Morse potential is suggested and studied analytically. The dependence of the Peierls-Nabarro potential on the system parameters is studied. Discrete traveling-wave solutions of a narrow permanent profile are shown to exist, depending on the anharmonicity of...

  11. Fe–Mn alloys: A mixed-bond spin-1/2 Ising model version

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, A.S. [Departamento de Física, Universidade Federal de Sergipe, 49100-000 São Cristovão, SE (Brazil); Albuquerque, Douglas F. de, E-mail: douglas@ufs.br [Departamento de Física, Universidade Federal de Sergipe, 49100-000 São Cristovão, SE (Brazil); Departamento de Matemática, Universidade Federal de Sergipe, 49100-000 São Cristovão, SE (Brazil); Moreno, N.O. [Departamento de Física, Universidade Federal de Sergipe, 49100-000 São Cristovão, SE (Brazil)

    2014-06-01

    In this work, we apply the mixed-bond spin-1/2 Ising model to study the magnetic properties of Fe–Mn alloys in the α phase by employing the effective field theory (EFT). Here, we suggest a new approach to the ferromagnetic coupling between nearest neighbours Fe–Fe that depends on the ratio between the Mn–Mn coupling and the Fe–Mn coupling and of second power of the Mn concentration q in contrast to linear dependence considered in the other articles. Also, we propose a new probability distribution for binary alloys with mixed-bonds based on the distribution for ternary alloys and we obtain a very good agreement for all considered values of q in T–q plane, in particular for q>0.11. - Highlights: • We apply the mixed-bond spin-1/2 to study the properties of Fe–Mn. • We employ the EFT and suggest a new approach to ferromagnetic coupling. • The new probability distribution is considered. • The phase diagram is obtained for all values of q in T–q plane.

  12. Models for calculation of dissociation energies of homonuclear diatomic molecules

    International Nuclear Information System (INIS)

    The variation of known dissociation energies of the transition metal diatomics across the Periodic Table is rather irregular like the bulk sublimation enthalpy, suggesting that the valence-bond model for bulk metallic systems might be applicable to the gaseous diatomic molecules and the various intermediate clusters. Available dissociation energies were converted to valence-state bonding energies considering various degrees of promotion to optimize the bonding. The degree of promotion of electrons to increase the number of bonding electrons is smaller than for the bulk, but the trends in bonding energy parallel the behavior found for the bulk metals. Thus using the established trends in bonding energies for the bulk elements, it was possible to calculate all unknown dissociation energies to provide a complete table of dissociation energies for all M2 molecules from H2 to Lr2. For solids such as Mg, Al, Si and most of the transition metals, large promotion energies are offset by strong bonding between the valence state atoms. The main question is whether bonding in the diatomics is adequate to sustain extensive promotion. The most extreme example for which a considerable difference would be expected between the bulk and the diatomics would be that of the Group IIA and IIB metals. The first section of this paper which deals with the alkaline earths Mg and Ca demonstrates a significant influence of the excited valence state even for these elements. The next section then expands the treatment to transition metals

  13. Modeling of a hydraulic excavator based on bond graph method and its parameter estimation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Soo Jin [Myongji University, Yongin (Korea, Republic of); Chang, Pyung Hun [Daegu Gyeongbuk Institute of Science and Technology, Daegu (Korea, Republic of)

    2012-01-15

    This paper focuses on two problems occurring in modeling a hydraulic excavator. The first problem arises in the modeling process. Because a hydraulic excavator has a very complex structure, the modeling process requires considerable time and is prone to errors. This problem is solved by conceptually modeling an excavator system using bond graph methods, the top-down and bottom-up methods, and the modeling software developed by the authors, and then, automatically deriving the nonlinear symbolic mathematical model from the conceptual model by using the modeling software. The other problem arises in obtaining parameters of the model. It is difficult to obtain the specification data for hydraulic components provided by manufacturers in general and to obtain the experimental data for estimating unique parameters. To solve this problem, an estimation method is devised for estimating parameters based on the experimental data that can be easily obtained. These methods enable easy and efficient modeling of an excavator system. In addition, the established model is verified through the comparison between the simulation and the experimental results. Also, this paper provides a good example of modeling of the large complex system.

  14. Modeling of a hydraulic excavator based on bond graph method and its parameter estimation

    International Nuclear Information System (INIS)

    This paper focuses on two problems occurring in modeling a hydraulic excavator. The first problem arises in the modeling process. Because a hydraulic excavator has a very complex structure, the modeling process requires considerable time and is prone to errors. This problem is solved by conceptually modeling an excavator system using bond graph methods, the top-down and bottom-up methods, and the modeling software developed by the authors, and then, automatically deriving the nonlinear symbolic mathematical model from the conceptual model by using the modeling software. The other problem arises in obtaining parameters of the model. It is difficult to obtain the specification data for hydraulic components provided by manufacturers in general and to obtain the experimental data for estimating unique parameters. To solve this problem, an estimation method is devised for estimating parameters based on the experimental data that can be easily obtained. These methods enable easy and efficient modeling of an excavator system. In addition, the established model is verified through the comparison between the simulation and the experimental results. Also, this paper provides a good example of modeling of the large complex system

  15. Unified model to predict flexural shear behavior of externally bonded RC beams

    International Nuclear Information System (INIS)

    Structural strengthening with externally bonded reinforcement is now recognized as a cost-effective, structurally sound and practically efficient method of rehabilitating deteriorating and damaged reinforced concrete beams. There is now an urgent need to develop a sound engineering basis which can predict the failure loads of all such strengthened beams in a reliable and consistent manner. Existing models to predict the behavior at ultimate of strengthened beams suffer from many limitations and weaknesses. This paper presents a unified global model, based on the Strut-and-Tie approach, to predict the failure loads of reinforced concrete beams strengthened for flexure and/or shear. This structural model is based on rational engineering principles, considers all the possible failure modes, and incorporates the load transfer mechanism bond to reflect the debonding phenomena which has a dominant influence on the failure process of plated beams. The model is validated against about 200 strengthened beam test reported in the literature and failing in flexure and/or shear, involving a large number of structural variables and steel, carbon and glass fiber reinforced polymer laminates as reinforcing medium. (author)

  16. Pricing the zero-coupon bond and its fair premium under a structural credit risk model with jumps

    OpenAIRE

    Dong, Yinghui; Wang, Guojing; Wu, Rong

    2011-01-01

    In this paper we consider a structural form credit risk model with jumps. We investigate the credit spread, the price, and the fair premium of the zero-coupon bond for the proposed model. The price and the fair premium of the bond are associated with the Laplace transform of default time and the firm's expected present market value at default. We give sufficient conditions under which the Laplace transform and the expected present market value of a firm at default are twice ...

  17. Quantum transport simulations of graphene nanoribbon devices using Dirac equation calibrated with tight-binding π-bond model

    OpenAIRE

    Chin, Sai-Kong; Lam, Kai-Tak; Seah, Dawei; Liang, Gengchiau

    2012-01-01

    We present an efficient approach to study the carrier transport in graphene nanoribbon (GNR) devices using the non-equilibrium Green's function approach (NEGF) based on the Dirac equation calibrated to the tight-binding π-bond model for graphene. The approach has the advantage of the computational efficiency of the Dirac equation and still captures sufficient quantitative details of the bandstructure from the tight-binding π-bond model for graphene. We demonstrate how the exact self-energies ...

  18. Method of modelization assistance with bond graphs and application to qualitative diagnosis of physical systems

    International Nuclear Information System (INIS)

    After having recalled the usual diagnosis techniques (failure index, decision tree) and those based on an artificial intelligence approach, the author reports a research aimed at exploring the knowledge and model generation technique. He focuses on the design of an aid to model generation tool and aid-to-diagnosis tool. The bond graph technique is shown to be adapted to the aid to model generation, and is then adapted to the aid to diagnosis. The developed tool is applied to three projects: DIADEME (a diagnosis system based on physical model), the improvement of the SEXTANT diagnosis system (an expert system for transient analysis), and the investigation on an Ariane 5 launcher component. Notably, the author uses the Reiter and Greiner algorithm

  19. Modelling Sovereign Bond Yield Curves of the US, Japan and Germany

    OpenAIRE

    Chi-sang Tam; Ip-wing Yu

    2007-01-01

    The movement of sovereign yields is important for both investment and risk management. In this paper, we apply a method that was first developed by Diebold et al (2006b) to model the sovereign bond yield curves of the US, Japan and Germany. By including observable macroeconomic variables and the latent factors of the yield curve, we find evidence of strong interaction between the yield curve and macro variables in the US and Germany but not in Japan. We also estimate the dynamic conditional c...

  20. Uncovering the secrets of the 2d random-bond Blume-Capel model

    OpenAIRE

    Malakis, A.; Berker, A. Nihat; Hadjiagapiou, I. A.; Fytas, N. G.; Papakonstantinou, T.

    2009-01-01

    The effects of bond randomness on the ground-state structure, phase diagram and critical behavior of the square lattice ferromagnetic Blume-Capel (BC) model are discussed. The calculation of ground states at strong disorder and large values of the crystal field is carried out by mapping the system onto a network and we search for a minimum cut by a maximum flow method. In finite temperatures the system is studied by an efficient two-stage Wang-Landau (WL) method for several values of the crys...

  1. Nishimori point in the 2D +/- J random-bond Ising model

    OpenAIRE

    A. Honecker; Picco, M.; Pujol, P.

    2000-01-01

    We study the universality class of the Nishimori point in the 2D +/- J random-bond Ising model by means of the numerical transfer-matrix method. Using the domain-wall free-energy, we locate the position of the fixed point along the Nishimori line at the critical concentration value p_c = 0.1094 +/- 0.0002 and estimate nu = 1.33 +/- 0.03. Then, we obtain the exponents for the moments of the spin-spin correlation functions as well as the value for the central charge c = 0.464 +/- 0.004. The mai...

  2. Bonding Strength Effects in Hydro-Mechanical Coupling Transport in Granular Porous Media by Pore-Scale Modeling

    Directory of Open Access Journals (Sweden)

    Zhiqiang Chen

    2016-03-01

    Full Text Available The hydro-mechanical coupling transport process of sand production is numerically investigated with special attention paid to the bonding effect between sand grains. By coupling the lattice Boltzmann method (LBM and the discrete element method (DEM, we are able to capture particles movements and fluid flows simultaneously. In order to account for the bonding effects on sand production, a contact bond model is introduced into the LBM-DEM framework. Our simulations first examine the experimental observation of “initial sand production is evoked by localized failure” and then show that the bonding or cement plays an important role in sand production. Lower bonding strength will lead to more sand production than higher bonding strength. It is also found that the influence of flow rate on sand production depends on the bonding strength in cemented granular media, and for low bonding strength sample, the higher the flow rate is, the more severe the erosion found in localized failure zone becomes.

  3. Network flow model of force transmission in unbonded and bonded granular media.

    Science.gov (United States)

    Tordesillas, Antoinette; Tobin, Steven T; Cil, Mehmet; Alshibli, Khalid; Behringer, Robert P

    2015-06-01

    An established aspect of force transmission in quasistatic deformation of granular media is the existence of a dual network of strongly versus weakly loaded particles. Despite significant interest, the regulation of strong and weak forces through the contact network remains poorly understood. We examine this aspect of force transmission using data on microstructural fabric from: (I) three-dimensional discrete element models of grain agglomerates of bonded subspheres constructed from in situ synchrotron microtomography images of silica sand grains under unconfined compression and (II) two-dimensional assemblies of unbonded photoelastic circular disks submitted to biaxial compression under constant volume. We model force transmission as a network flow and solve the maximum flow-minimum cost (MFMC) problem, the solution to which yields a percolating subnetwork of contacts that transmits the "maximum flow" (i.e., the highest units of force) at "least cost" (i.e., the dissipated energy from such transmission). We find the MFMC describes a two-tier hierarchical architecture. At the local level, it encapsulates intraconnections between particles in individual force chains and in their conjoined 3-cycles, with the most common configuration having at least one force chain contact experiencing frustrated rotation. At the global level, the MFMC encapsulates interconnections between force chains. The MFMC can be used to predict most of the force chain particles without need for any information on contact forces, thereby suggesting the network flow framework may have potential broad utility in the modeling of force transmission in unbonded and bonded granular media. PMID:26172702

  4. Bond Graph Modelling for Fault Detection and Isolation of an Ultrasonic Linear Motor

    Directory of Open Access Journals (Sweden)

    Mabrouk KHEMLICHE

    2010-12-01

    Full Text Available In this paper Bond Graph modeling, simulation and monitoring of ultrasonic linear motors are presented. Only the vibration of piezoelectric ceramics and stator will be taken into account. Contact problems between stator and rotor are not treated here. So, standing and travelling waves will be briefly presented since the majority of the motors use another wave type to generate the stator vibration and thus obtain the elliptic trajectory of the points on the surface of the stator in the first time. Then, electric equivalent circuit will be presented with the aim for giving a general idea of another way of graphical modelling of the vibrator introduced and developed. The simulations of an ultrasonic linear motor are then performed and experimental results on a prototype built at the laboratory are presented. Finally, validation of the Bond Graph method for modelling is carried out, comparing both simulation and experiment results. This paper describes the application of the FDI approach to an electrical system. We demonstrate the FDI effectiveness with real data collected from our automotive test. We introduce the analysis of the problem involved in the faults localization in this process. We propose a method of fault detection applied to the diagnosis and to determine the gravity of a detected fault. We show the possibilities of application of the new approaches to the complex system control.

  5. 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.

  6. Effects of Nb and Si on densities of valence electrons in bulk and defects of Fe3Al alloys

    Institute of Scientific and Technical Information of China (English)

    邓文; 钟夏平; 黄宇阳; 熊良钺; 王淑荷; 郭建亭; 龙期威

    1999-01-01

    Positron lifetime measurements have been performed in binary Fe3Al and Fe3Al doping with Nb or Si alloys. The densities of valence electrons of the bulk and microdefects in all tested samples have been calculated by using the positron lifetime parameters. Density of valence electron is low in the bulk of Fe3Al alloy. It indicates that, the 3d electrons in a Fe atom have strong-localized properties and tend to form covalent bonds with Al atoms, and the bonding nature in Fe3Al is a mixture of metallic and covalent bonds. The density of valence electron is very low in the defects of Fe3Al grain boundary, which makes the bonding cohesion in grain boundary quite weak. The addition of Si to Fe3Al gives rise to the decrease of the densities of valence electrons in the bulk and the grain boundary thus the metallic bonding cohesion. This makes the alloy more brittle. The addition of Nb to Fe3Al results in the decrease of the ordering energy of the alloy and increases the density of valence electron and th

  7. AVE bond index in the H-bond of the Watson-Crick pairs

    International Nuclear Information System (INIS)

    The normal Watson-Crick base pairs are treated as super-molecules. The properties of the electronic distribution along the N-H...Y bonds are studied in an all-valence-electrons calculation, through a bond index formula devised for non-orthogonal basis. Eletronic density diagrams of the adenine-uracil base pair are analysed. (Auhor)

  8. Modified virtual internal bond model for concrete subjected to dynamic loading

    Science.gov (United States)

    Patil, Mayuri

    Concrete is often used as a primary material to build protective structures. There is a wide range of research work being performed to simulate the behavior of reinforced concrete under impact and blast loading. This behavior is studied from both material and structural points of view. The research study presented in this thesis focuses on material aspects of modeling. LS-DYNARTM is an effective software for modeling and finite element analysis of structural members. It allows the user to define the material through commercially available or user-defined constitutive material models. Each material model has a distinct set of parameters to define a material which is further assigned to elements and used for simulations. This research study presents a user defined material model called Modified Concrete Virtual Internal Bond Model (MC-VIB). The basic constitutive model of VIB assumes the body as a collection of randomly oriented material points interconnected by a network of internal bonds. The model was modified by several researchers for different purposes. This research presents the MC-VIB for concrete under dynamic loading and studies its implementation into LS-DYNARTM. The modifications include incorporation of shear behavior and accounting for the difference in behavior of concrete in tension and compression. This project includes the calibration of the model based on stress-strain behavior of single element and cylinder model of concrete. The parameters are based on concrete with a uniaxial compressive strength of 27.6 MPa (4 ksi). These numerical curves are compared to those obtained from conventionally used material models for concrete and standard curves obtained by accepted equations to check the accuracy of prediction. The material model available in LS-DYNARTM requires a number of input parameters to define concrete behavior. These properties are normally derived from actual tests performed on the concrete under consideration. Often the properties are

  9. Valence instabilities as a source of actinide system inconsistencies

    International Nuclear Information System (INIS)

    Light actinide elements alone, and in some of their alloys, may exist as a static or dynamic mixture of two configurations. Such a state can explain both a resistivity maximum and lack of magnetic order observed in so many actinide materials, and still be compatible with the existence of f-electrons in narrow bands. Impurity elements may stabilize slightly different intermediate valence states in U, Np, and Pu, thus contributing to inconsistencies in published results. The physical property behavior of mixed-valence, rare-earth compounds is very much like that observed in development of antiphase (martensitic) structures. Martensitic transformations in U, Np, and Pu, from high-temperature b. c. c. to alpha phase, may be a way of ordering an alloy-like metal of mixed or intermediate valence. The relative stability of each phase structure may depend upon its electron-valence ratio. A Hubbard model for electron correlations in a narrow energy band has been invoked in most recent theories for explaining light actinide behavior. Such a model may also be applicable to crystal symmetry changes in martensitic transformations in actinides

  10. Dissociable modulation of overt visual attention in valence and arousal revealed by topology of scan path.

    Directory of Open Access Journals (Sweden)

    Jianguang Ni

    Full Text Available Emotional stimuli have evolutionary significance for the survival of organisms; therefore, they are attention-grabbing and are processed preferentially. The neural underpinnings of two principle emotional dimensions in affective space, valence (degree of pleasantness and arousal (intensity of evoked emotion, have been shown to be dissociable in the olfactory, gustatory and memory systems. However, the separable roles of valence and arousal in scene perception are poorly understood. In this study, we asked how these two emotional dimensions modulate overt visual attention. Twenty-two healthy volunteers freely viewed images from the International Affective Picture System (IAPS that were graded for affective levels of valence and arousal (high, medium, and low. Subjects' heads were immobilized and eye movements were recorded by camera to track overt shifts of visual attention. Algebraic graph-based approaches were introduced to model scan paths as weighted undirected path graphs, generating global topology metrics that characterize the algebraic connectivity of scan paths. Our data suggest that human subjects show different scanning patterns to stimuli with different affective ratings. Valence salient stimuli (with neutral arousal elicited faster and larger shifts of attention, while arousal salient stimuli (with neutral valence elicited local scanning, dense attention allocation and deep processing. Furthermore, our model revealed that the modulatory effect of valence was linearly related to the valence level, whereas the relation between the modulatory effect and the level of arousal was nonlinear. Hence, visual attention seems to be modulated by mechanisms that are separate for valence and arousal.

  11. 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.

  12. Molecular modeling of hydrogen bonding fluids: Vapor-liquid coexistence and interfacial properties

    CERN Document Server

    Horsch, Martin; Merker, Thorsten; Schnabel, Thorsten; Huang, Yow-Lin; Hasse, Hans; Vrabec, Jadran

    2010-01-01

    A major challenge for molecular modeling consists in optimizing the unlike interaction potentials. In many cases, combination rules are generally suboptimal when accurate predictions of properties like the mixture vapor pressure are needed. However, the well known Lorentz-Berthelot rule performs quite well and can be used as a starting point. If more accurate results are required, it is advisable to adjust the dispersive interaction energy parameter. In the present study, mixture properties are explored for binary systems containing hydrogen bonding components. Furthermore, vapor-liquid interface cluster criteria and contact angles are discussed and remarks on computational details are given. Finally, a sterically accurate generic model for benzyl alcohol is introduced and evaluated.

  13. DEM investigation of weathered rocks using a novel bond contact model

    Institute of Scientific and Technical Information of China (English)

    Zhenming Shi; Tao Jiang; Mingjing Jiang; Fang Liu; Ning Zhang

    2015-01-01

    The distinct element method (DEM) incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by para-metric simulations. In addition, weathering has a significant impact on both stressestrain relationship and failure pattern of rocks.

  14. Analytical model of asymmetrical Mixed-Mode Bending test of adhesively bonded GFRP joint

    Directory of Open Access Journals (Sweden)

    M. Ševčík

    2015-10-01

    Full Text Available This paper presents new analytical model of asymmetric mixed-mode bending (MMB specimen of adhesively bonded pultruded GFRP joints. An easily applicable relationship for the calculation of the strain energy release rate of the asymmetric MMB specimens is proposed based on the beam theory. The model is capable to analyze stacking sequence as well as various crack propagation paths. In the paper the effect of the various fiber bridging length and different crack propagation paths is analyzed analytically and supported by experimental results. The methodology and results presented in this paper could be utilized for the design of both joint geometry and lay-up of the laminates constituting the joint or for the prediction of the fracture behavior of such structures.

  15. Mechanical strength model for plastic bonded granular materials at high strain rates and large strains

    International Nuclear Information System (INIS)

    Modeling impact events on systems containing plastic bonded explosive materials requires accurate models for stress evolution at high strain rates out to large strains. For example, in the Steven test geometry reactions occur after strains of 0.5 or more are reached for PBX-9501. The morphology of this class of materials and properties of the constituents are briefly described. We then review the viscoelastic behavior observed at small strains for this class of material, and evaluate large strain models used for granular materials such as cap models. Dilatation under shearing deformations of the PBX is experimentally observed and is one of the key features modeled in cap style plasticity theories, together with bulk plastic flow at high pressures. We propose a model that combines viscoelastic behavior at small strains but adds intergranular stresses at larger strains. A procedure using numerical simulations and comparisons with results from flyer plate tests and low rate uniaxial stress tests is used to develop a rough set of constants for PBX-9501. Comparisons with the high rate flyer plate tests demonstrate that the observed characteristic behavior is captured by this viscoelastic based model. copyright 1998 American Institute of Physics

  16. Non-Shock Initiation Model for Plastic Bonded Explosive PBXN-5 and Cast Explosive: Experimental Results

    Science.gov (United States)

    Anderson, Mark; Todd, Steven; Caipen, Terry; Jensen, Charlie; Hughs, Chance

    2009-06-01

    A damage initiated reaction (DMGIR) computational model is being developed for the CTH shock physics code to predict the response of an explosive to non-shock mechanical insults. The distinguishing feature of this model is the introduction of a damage variable, which relates the evolution of damage to the initiation of reaction in the explosive, and its growth to detonation. The DMGIR model is a complement to the History Variable Reactive Burn (HVRB) model embedded in the current CTH code. Specifically designed experiments are supporting the development, implementation, and validation of the DMGIR numerical approach. PBXN-5 was the initial explosive material used experimentally to develop the DMGIR model. This explosive represents a family of plastically bonded explosives with good mechanical strength and rigid body properties. The model has been extended to cast explosives represented by Composition B. Furthermore, the DMGIR model will extended to predict results of non-shock mechanical insults for moldable plastic explosives such as C4 and PrimaSheet.

  17. Non-Shock Initiation Model for Plastic Bonded Explosive PBXN-5 and Cast Explosive

    Science.gov (United States)

    Todd, Steven; Caipen, Terry; Grady, Dennis; Anderson, Mark

    2009-06-01

    A damage initiated reaction (DMGIR) computational model is being developed for the CTH shock physics code to predict the response of an explosive to non-shock mechanical insults. The distinguishing feature of this model is the introduction of a damage variable, which relates the evolution of damage to the initiation of reaction in the explosive, and its growth to detonation. The DMGIR model is a complement to the History Variable Reactive Burn (HVRB) model embedded in the current CTH code. Specifically designed experiments are supporting the development, implementation, and validation of the DMGIR numerical approach. PBXN-5 was the initial explosive material used experimentally to develop the DMGIR model. This explosive represents a family of plastically bonded explosives with good mechanical strength and rigid body properties. The model has been extended to cast explosives represented by Composition B. Furthermore, the DMGIR model will extended to predict results of non-shock mechanical insults for moldable plastic explosives such as C4 and PrimaSheet.

  18. Monte Carlo simulations of two-dimensional Hubbard models with string bond tensor-network states

    Science.gov (United States)

    Song, Jeong-Pil; Wee, Daehyun; Clay, R. T.

    2015-03-01

    We study charge- and spin-ordered states in the two-dimensional extended Hubbard model on a triangular lattice at 1/3 filling. While the nearest-neighbor Coulomb repulsion V induces charge-ordered states, the competition between on-site U and nearest-neighbor V interactions lead to quantum phase transitions to an antiferromagnetic spin-ordered phase with honeycomb charge order. In order to avoid the fermion sign problem and handle frustrations here we use quantum Monte Carlo methods with the string-bond tensor network ansatz for fermionic systems in two dimensions. We determine the phase boundaries of the several spin- and charge-ordered states and show a phase diagram in the on-site U and the nearest-neighbor V plane. The numerical accuracy of the method is compared with exact diagonalization results in terms of the size of matrices D. We also test the use of lattice symmetries to improve the string-bond ansatz. Work at Mississippi State University was supported by the US Department of Energy grant DE-FG02-06ER46315.

  19. Enzymatic Transformation and Bonding of Sulfonamide Antibiotics to Model Humic Substances

    Directory of Open Access Journals (Sweden)

    J. Schwarz

    2015-01-01

    Full Text Available Sulfonamides are consumed as pharmaceutical antibiotics and reach agricultural soils with excreta used as fertilizer. Subsequently, nonextractable residues rapidly form in soil, which has been researched in a couple of studies. To further elucidate conditions, strength, and mechanisms of the fixation to soil humic substances, three selected sulfonamides were investigated using the biochemical oligomerization of substituted phenols as a model for the humification process. Catechol, guaiacol, and vanillin were enzymatically reacted using laccase from Trametes versicolor. In the presence of the substituted phenols alone, the concentration of sulfonamides decreased. This decrease was even more pronounced when additional laccase was present. Upon the enzymatic oligomerization of the substituted phenols to a humic-like structure the sulfonamides were sorbed, transformed, sequestered, and nonextractable bound. Sulfonamides were transformed depending on their molecular properties. Fractions of different bonding strength were determined using a sequential extraction procedure. Isolated nonextractable products were analyzed by chromatographic, spectroscopic, and calorimetric methods to identify coupling and bonding mechanisms of the sulfonamides. Differential scanning calorimetry measurements suggested cross-linking of such incorporated sulfonamides in humic oligomers. Nuclear magnetic resonance spectroscopy measurements showed clear differences between the vanillin-sulfapyridine oligomer and the parent sulfapyridine indicating bound residue formation through covalent binding.

  20. Implementation of strength and burn models for plastic-bonded explosives and propellants

    Energy Technology Data Exchange (ETDEWEB)

    Reaugh, J E

    2009-05-07

    We have implemented the burn model in LS-DYNA. At present, the damage (porosity and specific surface area) is specified as initial conditions. However, history variables that are used by the strength model are reserved as placeholders for the next major revision, which will be a completely interactive model. We have implemented an improved strength model for explosives based on a model for concrete. The model exhibits peak strength and subsequent strain softening in uniaxial compression. The peak strength increases with increasing strain rate and/or reduced ambient temperature. Under triaxial compression compression, the strength continues to increase (or at least not decrease) with increasing strain. This behaviour is common to both concrete and polymer-bonded explosives (PBX) because the microstructure of these composites is similar. Both have aggregate material with a broad particle size distribution, although the length scale for concrete aggregate is two orders of magnitude larger than for PBX. The (cement or polymer) binder adheres to the aggregate, and is both pressure and rate sensitive. There is a larger bind binder content in concrete, compared to the explosive, and the aggregates have different hardness. As a result we expect the parameter values to differ, but the functional forms to be applicable to both. The models have been fit to data from tests on an AWE explosive that is HMX based. The decision to implement the models in LS-DYNA was based on three factors: LS-DYNA is used routinely by the AWE engineering analysis group and has a broad base of experienced users; models implemented in LS-DYNA can be transferred easily to LLNL's ALE 3D using a material model wrapper developed by Rich Becker; and LS-DYNA could accommodate the model requirements for a significant number of additional history variables without the significant time delay associated with code modification.

  1. Valence instabilities in cerium intermetallics

    International Nuclear Information System (INIS)

    The primary purpose of this investigation was to study the magnetic behaviour of cerium in intermetallic compounds, that show an IV behaviour, e.g. CeSn3. In the progress of the investigations, it became of interest to study the effect of changes in the lattice of the IV compound by substituting La or Y for Ce, thus constituting the Cesub(1-x)Lasub(x)Sn3 and Cesub(1-x)Ysub(x)Sn3 quasibinary systems. A second purpose was to examine the possibility of introducing instabilities in the valency of a trivalent intermetallic cerium compound: CeIn3, also by La and Y-substitutions in the lattice. Measurements on the resulting Cesub(1-x)Lasub(x)In3 and Cesub(1-x)Ysub(x)In3 quasibinaries are described. A third purpose was to study the (gradual) transition from a trivalent cerium compound into an IV cerium compound. This was done by examining the magnetic properties of the CeInsub(x)Snsub(3-x) and CePbsub(x)Snsub(3-x) systems. Finally a new possibility was investigated: that of the occurrence of IV behaviour in CeSi2, CeSi, and in CeGa2. (Auth.)

  2. Avoided valence transition in a plutonium superconductor.

    Science.gov (United States)

    Ramshaw, B J; Shekhter, Arkady; McDonald, Ross D; Betts, Jon B; Mitchell, J N; Tobash, P H; Mielke, C H; Bauer, E D; Migliori, Albert

    2015-03-17

    The d and f electrons in correlated metals are often neither fully localized around their host nuclei nor fully itinerant. This localized/itinerant duality underlies the correlated electronic states of the high-Tc cuprate superconductors and the heavy-fermion intermetallics and is nowhere more apparent than in the 5f valence electrons of plutonium. Here, we report the full set of symmetry-resolved elastic moduli of PuCoGa5--the highest Tc superconductor of the heavy fermions (Tc = 18.5 K)--and find that the bulk modulus softens anomalously over a wide range in temperature above Tc. The elastic symmetry channel in which this softening occurs is characteristic of a valence instability--therefore, we identify the elastic softening with fluctuations of the plutonium 5f mixed-valence state. These valence fluctuations disappear when the superconducting gap opens at Tc, suggesting that electrons near the Fermi surface play an essential role in the mixed-valence physics of this system and that PuCoGa5 avoids a valence transition by entering the superconducting state. The lack of magnetism in PuCoGa5 has made it difficult to reconcile with most other heavy-fermion superconductors, where superconductivity is generally believed to be mediated by magnetic fluctuations. Our observations suggest that valence fluctuations play a critical role in the unusually high Tc of PuCoGa5. PMID:25737548

  3. Quantum transport simulations of graphene nanoribbon devices using Dirac equation calibrated with tight-binding π-bond model.

    Science.gov (United States)

    Chin, Sai-Kong; Lam, Kai-Tak; Seah, Dawei; Liang, Gengchiau

    2012-01-01

    We present an efficient approach to study the carrier transport in graphene nanoribbon (GNR) devices using the non-equilibrium Green's function approach (NEGF) based on the Dirac equation calibrated to the tight-binding π-bond model for graphene. The approach has the advantage of the computational efficiency of the Dirac equation and still captures sufficient quantitative details of the bandstructure from the tight-binding π-bond model for graphene. We demonstrate how the exact self-energies due to the leads can be calculated in the NEGF-Dirac model. We apply our approach to GNR systems of different widths subjecting to different potential profiles to characterize their device physics. Specifically, the validity and accuracy of our approach will be demonstrated by benchmarking the density of states and transmissions characteristics with that of the more expensive transport calculations for the tight-binding π-bond model. PMID:22325480

  4. Microscopic models for proton transfer in water and strongly hydrogen-bonded complexes with a single-well proton potential

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2004-01-01

    A new mechanism and formalism for proton transfer in donor-acceptor complexes with long hydrogen bonds introduced recently [1], is applied to a proton transfer in liquid water. "Structural diffusion" of hydroxonium ions is regarded as totally adiabatic process, with synchronous hindered translation...... of two closest water molecules to and from the reaction complex as crucial steps. The water molecules induce a "gated" shift of the proton from the donor to the acceptor in the double-well potential with simultaneous breaking/formation of hydrogen bonds between these molecules and the proton donor...... hydrogen-bonded donor-acceptor complexes. In contrast to the above model [1], the short hydrogen bond between the donor and acceptor moieties, however, completely erodes the barrier along the proton transfer mode. This introduces some physical pattern differences from proton transfer reactions in truly...

  5. Method of determining radioactive atom valence

    International Nuclear Information System (INIS)

    The valency state of radionuclides emitting low-energy conversion electrons is determined from the measured change in kinetic energies of conversion electrons which is determined by electron spectroscopy. The determined changes in kinetic energies correspond to changes in binding energies of electrons in the atomic shell which are related to the valency state of the radionuclides. The advantage of the method is the possibility of determining valency states in trace amounts of radioactive substances, its nondestructive character and high sensitivity (10-11g). (E.S.)

  6. Modeling Progressive Failure of Bonded Joints Using a Single Joint Finite Element

    Science.gov (United States)

    Stapleton, Scott E.; Waas, Anthony M.; Bednarcyk, Brett A.

    2010-01-01

    Enhanced finite elements are elements with an embedded analytical solution which can capture detailed local fields, enabling more efficient, mesh-independent finite element analysis. In the present study, an enhanced finite element is applied to generate a general framework capable of modeling an array of joint types. The joint field equations are derived using the principle of minimum potential energy, and the resulting solutions for the displacement fields are used to generate shape functions and a stiffness matrix for a single joint finite element. This single finite element thus captures the detailed stress and strain fields within the bonded joint, but it can function within a broader structural finite element model. The costs associated with a fine mesh of the joint can thus be avoided while still obtaining a detailed solution for the joint. Additionally, the capability to model non-linear adhesive constitutive behavior has been included within the method, and progressive failure of the adhesive can be modeled by using a strain-based failure criteria and re-sizing the joint as the adhesive fails. Results of the model compare favorably with experimental and finite element results.

  7. Modeling of metal–oxide semiconductor: Analytical bond-order potential for cupric oxide

    International Nuclear Information System (INIS)

    Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, “Erratum: Empirical potential for hydrocarbons for use in simulating the chemical vapor deposition of diamond films”, Phys. Rev. B 1992, 46 1948]. In this paper, for the pure cupric element, the energy and structural parameters for several bulk phases as well as dimmer structure are well reproduced. The reference data are taken from our density functional theory calculations and the available experiments. The model potential also provides a good description of the bulk properties of various solid structures of cupric oxide compound structures, including cohesive energies, lattice parameters, and elastic constants. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  8. Exact transverse susceptibility of one-dimensional random bond Ising model with alternating spin

    International Nuclear Information System (INIS)

    The zero-field transverse susceptibility of a one-dimensional random bond Ising model with alternating spin 1/2 and S is exactly obtained. The integral form of the susceptibility is written. The thermal curve of the susceptibility becomes irregular when weak interactions appear with a small probability. The leading-order terms of an expansion, in terms of the moment of the distribution of a random variable, are obtained. The first-order term vanishes and the second-order term is written explicitly. The expansion up to infinite order is exactly obtained in the case of uniform spin S = 1/2. The classical limit S → ∞ is also considered. It is found that the low-temperature limit T → 0 of the susceptibility is independent of S. (paper)

  9. Universality Class of the Nishimori Point in the 2D +/-J Random-Bond Ising Model

    Science.gov (United States)

    Honecker, A.; Picco, M.; Pujol, P.

    2001-07-01

    We study the universality class of the Nishimori point in the 2D +/-J random-bond Ising model by means of the numerical transfer-matrix method. Using the domain-wall free energy, we locate the position of the fixed point along the Nishimori line at the critical concentration value pc = 0.1094+/-0.0002 and estimate ν = 1.33+/-0.03. Then, we obtain the exponents for the moments of the spin-spin correlation functions as well as the value for the central charge c = 0.464+/-0.004. The main qualitative result is the fact that percolation is now excluded as a candidate for describing the universality class of this fixed point.

  10. Universality Class of the Nishimori Point in the 2D {+-}J Random-Bond Ising Model

    Energy Technology Data Exchange (ETDEWEB)

    Honecker, A.; Picco, M.; Pujol, P.

    2001-07-23

    We study the universality class of the Nishimori point in the 2D {+-}J random-bond Ising model by means of the numerical transfer-matrix method. Using the domain-wall free energy, we locate the position of the fixed point along the Nishimori line at the critical concentration value p{sub c}=0.1094{+-}0.0002 and estimate {nu}=1.33{+-}0.03 . Then, we obtain the exponents for the moments of the spin-spin correlation functions as well as the value for the central charge c=0.464{+-}0.004 . The main qualitative result is the fact that percolation is now excluded as a candidate for describing the universality class of this fixed point.

  11. Mass spectrometric determination of atomization energies of inorganic molecules and their correlation by empirical models of bonding

    International Nuclear Information System (INIS)

    The application of the Knudsen effusion method combined with mass spectrometry for the measurement of atomization energies of inorganic molecules is described. Recent results with emphasis on molecular metals, intermetallic molecules and metal carbides are presented. The use and limitations of various empirica models of bonding are illustrated by comparing experimental values with those calculated by the various models

  12. Molecular mechanism of acid-catalyzed hydrolysis of peptide bonds using a model compound.

    Science.gov (United States)

    Pan, Bin; Ricci, Margaret S; Trout, Bernhardt L

    2010-04-01

    The stability of peptide bonds is a critical aspect of biological chemistry and therapeutic protein applications. Recent studies found elevated nonenzymatic hydrolysis in the hinge region of antibody molecules, but no mechanism was identified. As a first step in providing a mechanistic interpretation, this computational study examines the rate-determining step of the hydrolytic reaction of a peptide bond under acidic pH by a path sampling technique using a model compound N-MAA. Most previous computational studies did not include explicit water molecules, whose effects are significant in solution chemistry, nor did they provide a dynamic picture for the reaction process in aqueous conditions. Because no single trajectory can be used to describe the reaction dynamics due to fluctuations at finite temperatures, a variant version of the transition path sampling technique, the aimless shooting algorithm, was used to sample dynamic trajectories and to generate an ensemble of transition trajectories according to their statistical weights in the trajectory space. Each trajectory was computed as the time evolution of the molecular system using the Car-Parrinello molecular dynamics technique. The likelihood maximization procedure and its modification were used in extracting dynamically relevant degrees of freedom in the system, and approximations of the reaction coordinate were compared. Its low log-likelihood score and poor p(B) histogram indicate that the C-O distance previously assumed as the reaction coordinate for the rate-determining step is inadequate in describing the dynamics of the reaction. More than one order parameter in a candidate set including millions of geometric quantities was required to produce a convergent reaction coordinate model; its involvement of many degrees of freedom suggests that this hydrolytic reaction step is very complex. In addition to affecting atoms directly involved in bond-making and -breaking processes, the water network also has

  13. Study of the steel concrete bonding: from modeling of phenomena to the formulation of a 'reinforced concrete' enhanced solid element

    International Nuclear Information System (INIS)

    Bonding is a very important item in Reinforced Concrete structures, because it is in reality a transferring zone of efforts and stresses between steel rebars and concrete. Our objective has been to take account of this phenomenon in numerical analysis of RC structures. In this study, we present a new non linear model for bonding behavior. Written in stress strain terms, the model is support by a 2D interface finite element. By the way, we report the model's parameters and we illustrate their use by some numerical examples. Finally, we propose a new brand formulation of an Enhanced Finite Element for simplifying RC analysis, considering the three main components: concrete bonding steel. (author)

  14. MESOSCALE MODELING OF DEFLAGRATION-INDUCED DECONSOLIDATION IN POLYMER-BONDED EXPLOSIVES

    Energy Technology Data Exchange (ETDEWEB)

    Springer, H K; Glascoe, E A; Reaugh, J E; Kercher, J R; Maienschein, J L

    2011-08-01

    Initially undamaged polymer-bonded explosives can transition from conductive burning to more violent convective burning via rapid deconsolidation at higher pressures. The pressure-dependent infiltration of cracks and pores, i.e., damage, by product gases at the burn-front is a key step in the transition to convective burning. However, the relative influence of pre-existing damage and the evolution of deflagration-induced damage during the transition to convective burning is not well understood. The objective of this study is to investigate the role of microstructure and initial pressurization on deconsolidation. We performed simulations using the multi-physics hydrocode, ALE3D. HMX-Viton A served as our model explosive. A Prout-Tompkins chemical kinetic model, Vielle's Law pressure-dependent burning, Gruneisen equation-of-state, and simplified strength model were used for the HMX. The propensity for deconsolidation increased with increasing defect size and decreasing initial pressurization, as measured by the increase in burning surface area. These studies are important because they enable the development of continuum-scale damage models and the design of inherently safer explosives.

  15. Development of Remote Plutonium Valence State Analyzer

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>In the Purex process of spent fuel reprocessing, the separation of uranium and plutonium depends on the capability extracting state plutonium ions with various valence by TBP. The separate degree of

  16. Valence nucleons in self-consistent fields

    International Nuclear Information System (INIS)

    An iterative approach to determine directly the best Hartree-Fock one-body density rho is extended by expressing rho in terms of a core and a valence part and allowing for general crossings of occupied and unoccupied levels in the valence part. Results are shown for 152Sm and a microscopic analysis of the core structure of deformed light nuclei is carried out. (author)

  17. Modeling of Covalent Bonding in Solids by Inversion of Cohesive Energy Curves

    OpenAIRE

    Bazant, Martin Z.; Kaxiras, Efthimios

    1996-01-01

    We provide a systematic test of empirical theories of covalent bonding in solids using an exact procedure to invert ab initio cohesive energy curves. By considering multiple structures of the same material, it is possible for the first time to test competing angular functions, expose inconsistencies in the basic assumption of a cluster expansion, and extract general features of covalent bonding. We test our methods on silicon, and provide the direct evidence that the Tersoff-type bond order f...

  18. Valence state parameters of all transition metal atoms in metalloproteins--development of ABEEMσπ fluctuating charge force field.

    Science.gov (United States)

    Yang, Zhong-Zhi; Wang, Jian-Jiang; Zhao, Dong-Xia

    2014-09-01

    To promote accuracy of the atom-bond electronegativity equalization method (ABEEMσπ) fluctuating charge polarizable force fields, and extend it to include all transition metal atoms, a new parameter, the reference charge is set up in the expression of the total energy potential function. We select over 700 model molecules most of which model metalloprotein molecules that come from Protein Data Bank. We set reference charges for different apparent valence states of transition metals and calibrate the parameters of reference charges, valence state electronegativities, and valence state hardnesses for ABEEMσπ through linear regression and least square method. These parameters can be used to calculate charge distributions of metalloproteins containing transition metal atoms (Sc-Zn, Y-Cd, and Lu-Hg). Compared the results of ABEEMσπ charge distributions with those obtained by ab initio method, the quite good linear correlations of the two kinds of charge distributions are shown. The reason why the STO-3G basis set in Mulliken population analysis for the parameter calibration is specially explained in detail. Furthermore, ABEEMσπ method can also quickly and quite accurately calculate dipole moments of molecules. Molecular dynamics optimizations of five metalloproteins as the examples show that their structures obtained by ABEEMσπ fluctuating charge polarizable force field are very close to the structures optimized by the ab initio MP2/6–311G method. This means that the ABEEMσπ/MM can now be applied to molecular dynamics simulations of systems that contain metalloproteins with good accuracy. PMID:25042901

  19. How resonance assists hydrogen bonding interactions: an energy decomposition analysis.

    Science.gov (United States)

    Beck, John Frederick; Mo, Yirong

    2007-01-15

    Block-localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance-assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between pi delocalization and hydrogen-bonding interactions. We examined the dimers of formic acid, formamide, 4-pyrimidinone, 2-pyridinone, 2-hydroxpyridine, and 2-hydroxycyclopenta-2,4-dien-1-one. In addition, we studied the interactions in beta-diketone enols with a simplified model, namely the hydrogen bonds of 3-hydroxypropenal with both ethenol and formaldehyde. The intermolecular interaction energies, either with or without the involvement of pi resonance, were decomposed into the Hitler-London energy (DeltaEHL), polarization energy (DeltaEpol), charge transfer energy (DeltaECT), and electron correlation energy (DeltaEcor) terms. This allows for the examination of the character of hydrogen bonds and the impact of pi conjugation on hydrogen bonding interactions. Although it has been proposed that resonance-assisted hydrogen bonds are accompanied with an increasing of covalency character, our analyses showed that the enhanced interactions mostly originate from the classical dipole-dipole (i.e., electrostatic) attraction, as resonance redistributes the electron density and increases the dipole moments in monomers. The covalency of hydrogen bonds, however, changes very little. This disputes the belief that RAHB is primarily covalent in nature. Accordingly, we recommend the term "resonance-assisted binding (RAB)" instead of "resonance-assisted hydrogen bonding (RHAB)" to highlight the electrostatic, which is a long-range effect, rather than the electron transfer nature of the enhanced stabilization in RAHBs. PMID:17143867

  20. Chalcogen bonding interactions between reducible sulfur and selenium compounds and models of zinc finger proteins.

    Science.gov (United States)

    Lutz, Patricia B; Bayse, Craig A

    2016-04-01

    Reducible sulfur and selenium (r-S/Se) compounds, defined as sulfur and selenium compounds not in the lowest -2 oxidation state (e.g., -1 to +6), release Zn(2+) from zinc-sulfur proteins such as zinc fingers (ZFs) and metallothionein. A series of density functional theory calculations was performed on donor-acceptor complexes between r-S/Se compounds and models of the Cys2His2, Cys3His and Cys4 ZF sites. These S⋯S/Se chalcogen bonding interactions consist of the donation of electron density from a S lone pair on the ZF model to a S/Se-X antibonding molecular orbital of the r-S/Se compound. The strength of the interaction was shown to be dependent upon the Lewis basicity of the ZF model (Cys4>Cys3His>Cys2His2) and the Lewis acidity of the r-S/Se compound as measured by the energy of the S/Se-X antibonding orbital. Interactions with the softer r-Se compounds were stronger than the r-S compounds, consistent with the greater reactivity of the former with ZF proteins. PMID:26877152

  1. A Corpuscular Picture of Electrons in Chemical Bond

    CERN Document Server

    Ando, Koji

    2015-01-01

    We introduce a theory of chemical bond with a corpuscular picture of electrons. It employs a minimal set of localized electron wave packets with 'floating and breathing' degrees of freedom and the spin-coupling of non-orthogonal valence-bond theory. It accurately describes chemical bonds in ground and excited states of spin singlet and triplet, in a distinct manner from conventional theories, indicating potential for establishing a dynamical theory of electrons in chemical bonds.

  2. Incremental Validity of Positive and Negative Valence in Predicting Personality Disorder

    OpenAIRE

    Simms, Leonard J.; Yufik, Tom; Gros, Daniel F.

    2010-01-01

    The Big Seven model of personality includes five dimensions similar to the Big Five model as well as two evaluative dimensions—Positive Valence (PV) and Negative Valence (NV)—which reflect extremely positive and negative person descriptors, respectively. Recent theory and research have suggested that PV and NV predict significant variance in personality disorder (PD) above that predicted by the Big Five, but firm conclusions have not been possible because previous studies have been limited to...

  3. AB INITIO STUDY ON VALENCE INDICES AND REACTIVITIES OF SOME BORAENS

    Institute of Scientific and Technical Information of China (English)

    曹阳; 王友良

    1991-01-01

    In the pressnt paper, 3-21G ab initio molecular orbital calculations arc performed on diborane B2H6 and the substituted bridged-atom species H4B2X2(X=F, C1, OH, NH2, CH3),and these geometries are optimized with the energy gradient technique. According to the quantum chemical definition of atomic valence, the valences of the bridged-atoms are calculated to studtd the characteristion of the bridging bond B-X-B. Some larger boranes B4H10, B5H9, and B5H11 are also calculated to discuss the valence indices and analyze the reactiveities of the bridged-atoms.

  4. Nuclear effects on valence quark distributions and sea quark distributions

    International Nuclear Information System (INIS)

    A method is presented to get nuclear effect functions RvA(xt) and Rsa(xt) on valence quark distributions and sea quark distributions from the data of 1-A DIS process and nuclear Drell-Yan process. Both the functions may be used to test the theoretical models explaining the nuclear effects. As a example, RvFe(xt) and RsFe(xt) of the iron nucleus were obtained by this method

  5. Discrete kink dynamics in hydrogen-bonded chains: The two-component model

    DEFF Research Database (Denmark)

    Karpan, V.M.; Zolotaryuk, Yaroslav; Christiansen, Peter Leth; Zolotaryuk, Alexander

    2004-01-01

    -proton interaction in the hydrogen bond. (ii) a harmonic coupling between the protons in adjacent hydrogen bonds, and (iii) a harmonic coupling between the nearest-neighbor heavy ions (an isolated diatomic chain with the lowest acoustic band) or instead a harmonic on-site potential for the heavy ions (a diatomic...

  6. A damage model to predict the durability of bonded assemblies. Part I : Debonding behavior of FRP strengthened concrete structures

    OpenAIRE

    Benzarti, Karim; Freddi, Francesco; Fremond, Michel

    2011-01-01

    Presented in this paper is a coupled damage model to predict the durability of concrete elements strengthened by external bonding of fiber reinforced polymer (FRP) plates. Both the concrete, the strengthening FRP and the glue are modeled as damageable materials. The damage model is developed within the framework of the principle of virtual power. The adopted power of the internal forces depends on the damage velocity and on its gradient to take into account local interactions. An interaction ...

  7. Modeling shock responses of plastic bonded explosives using material point method

    Science.gov (United States)

    Shang, Hailin; Zhao, Feng; Fu, Hua

    2015-06-01

    Shock responses of plastic bonded explosives are modeled using material point method as implemented in the Uintah Computational Framework. The two-dimensional geometrical model was established based on the micrograph of PBX9501. Shock loading for this explosive was performed by a piston moving at a constant velocity. Simulation results indicate that under shock loading there forms some stress localizations on the grain boundary of HMX explosive. These stress localizations lead to some serious plastic deformation. Simultaneously, the plastic strain energy transforms to thermal energy, causing the temperature to rise rapidly and form some hot spots on grain boundary areas. There are also some micro cracks appear at early time of the shock loading. But after some time these cracks begin to close, forming a few hot spots. The influence of shock strength on the responses of explosive was also investigated by increasing the piston velocity. And the results show that with increasing shock strength, the distribution of plastic strain and temperature does not have significant change, but their values increase obviously. Namely, the higher the shock strength is, the higher the hot spot temperature will be. Supported by the National Natural Science Foundation of China (11272296).

  8. Strength Modeling of Reinforced Concrete Beam with Externally Bonded FRP Reinforcement

    Directory of Open Access Journals (Sweden)

    N. Pannirselvam

    2008-01-01

    Full Text Available This research study presents the evaluation of the structural behaviour of reinforced concrete beams with externally bonded Fibre Reinforced Polymer (FRP reinforcements. Three different steel ratios with two different Glass Fibre Reinforced Polymer (GFRP types and two different thicknesses in each type of GFRP were used. Totally fifteen rectangular beams of 3 m length were cast. Three rectangular beams were used as reference beam (Control Beams and the remaining were fixed with GFRP laminates on the soffit of the rectangular beam. The variables considered for the study includes longitudinal steel ratio, type of GFRP laminates, thickness of GFRP laminates and composite ratios. Flexural test, using simple beam with third-point loading was adopted to study the performance of FRP plated beams interms flexural strength, deflection, ductility and was compared with the unplated beams. The test results show that the beams strengthened with GFRP laminates exhibit better performance. The flexural strength and ductility increase with increase in thickness of GFRP plate. The increase in first crack loads was up to 88.89% for 3 mm thick WRGFRP plates and 100.00% for 5 mm WRGFRP plated beams and increase in ductility interms of energy and deflection was found to be 56.01 and 64.69% respectively with 5 mm thick GFRP plated beam. Strength models were developed for predicting the flexural strength (ultimate load, service load and ductility of FRP beams. The strength model developed give prediction matching the measurements.

  9. DEM investigation of weathered rocks using a novel bond contact model

    Directory of Open Access Journals (Sweden)

    Zhenming Shi

    2015-06-01

    Full Text Available The distinct element method (DEM incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by parametric simulations. In addition, weathering has a significant impact on both stress–strain relationship and failure pattern of rocks.

  10. The role of the autonomic nervous system in hypertension: a bond graph model study

    International Nuclear Information System (INIS)

    A bond graph model of the cardiovascular system with embedded autonomic nervous regulation was developed for a better understanding of the role of the autonomic nervous system (ANS) in hypertension. The model is described by a pump model of the heart and a detailed representation of the head and neck, pulmonary, coronary, abdomen and extremity circulation. It responds to sympathetic and parasympathetic activities by modifying systemic peripheral vascular resistance, heart rate, ventricular end-systolic elastance and venous unstressed volumes. The impairment of ANS is represented by an elevation of the baroreflex set point. The simulation results show that, compared with normotensive, in hypertension the systolic and diastolic blood pressure (SBP/DBP) rose from 112/77 mmHg to 144/94 mmHg and the left ventricular wall thickness (LVWT) increased from 10 mm to 12.74 mm. In the case that ANS regulation was absent, both the SBP and DBP further increased by 8 mmHg and the LVWT increased to 13.22 mm. The results also demonstrate that when ANS regulation is not severely damaged, e.g. the baroreflex set point is 97 mmHg, it still has an effect in preventing the rapid rise of blood pressure in hypertension; however, with the worsening of ANS regulation, its protective role weakens. The results agree with human physiological and pathological features in hemodynamic parameters and carotid baroreflex function curves, and indicate the role of ANS in blood pressure regulation and heart protection. In conclusion, the present model may provide a valid approach to study the pathophysiological conditions of the cardiovascular system and the mechanism of ANS regulation

  11. On valence electron density, energy dissipation and plasticity of bulk metallic glasses

    International Nuclear Information System (INIS)

    Highlights: ► Relationship between valence electron density and plasticity of metallic glasses. ► Poisson's ratio increases as electron density decreases. ► Energy dissipation proposed to understand plasticity. ► Low electron density indicates small activation energy. -- Abstract: In conventional crystalline alloys, valence electron density (VED) is one of the most significant factors in determining their phase stability and mechanical properties. Extending the concept to metallic glasses (MGs), it is found, not totally surprisingly, that their mechanical properties are VED-dependent as in crystalline alloys. Interestingly, the whole VED region can be separated into two zones: Zone 1 consists of Mg-, Ca-, and RE-based (RE for rare earth) alloys; Zone 2 consists of the rest of MGs. In either zone, for each type of MGs, Poisson's ratio generally decreases as VED increases. From the energy dissipation viewpoint proposed recently, the amorphous plasticity is closely related to the activation energy for the operation of shear-transformation-zones (STZs). Smaller STZ activation energy suggests higher ductility because STZs with lower activation energy are able to convert deformation work more efficiently into configurational energy rather than heat, which yields mechanical softening and advances the growth of shear bands (SBs). Following this model, it is revealed that the activation energies for STZ operation and crystallization are certainly proportional to VED. Thus, it is understood that, in Zone 2, MGs have a smaller VED and hence lower activation energies which are favorable for ductility and Poisson's ratio. In Zone 1, MGs have the lowest VED but apparent brittleness because either of low glass transition temperature and poor resistance to oxidation or of a large fraction of covalent bonds

  12. X-ray Emission Spectroscopy to Study Ligand Valence Orbitals in Mn Coordination Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Smolentsev, Grigory; Soldatov, Alexander V; Messinger, Johannes; Merz, Kathrin; Weyhermuller, Thomas; Bergmann, Uwe; Pushkar, Yulia; Yano, Junko; Yachandra, Vittal K.; Glatzel, Pieter

    2009-03-02

    We discuss a spectroscopic method to determine the character of chemical bonding and for the identification of metal ligands in coordination and bioinorganic chemistry. It is based on the analysis of satellite lines in X-ray emission spectra that arise from transitions between valence orbitals and the metal ion 1s level (valence-to-core XES). The spectra, in connection with calculations based on density functional theory (DFT), provide information that is complementary to other spectroscopic techniques, in particular X-ray absorption (XANES and EXAFS). The spectral shape is sensitive to protonation of ligands and allows ligands, which differ only slightly in atomic number (e.g., C, N, O...), to be distinguished. A theoretical discussion of the main spectral features is presented in terms of molecular orbitals for a series of Mn model systems: [Mn(H2O)6]2+, [Mn(H2O)5OH]+, [Mn(H2O)5NH2]+, and [Mn(H2O)5NH3]2+. An application of the method, with comparison between theory and experiment, is presented for the solvated Mn2+ ion in water and three Mn coordination complexes, namely [LMn(acac)N3]BPh4, [LMn(B2O3Ph2)(ClO4)], and [LMn(acac)N]BPh4, where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane, acac stands for the 2,4-pentanedionate anion, and B2O3Ph2 represents the 1,3-diphenyl-1,3-dibora-2-oxapropane-1,3-diolato dianion.

  13. Theoretical calculations of valence states in Fe-Mo compounds

    International Nuclear Information System (INIS)

    The half-metallic ferromagnetic double perovskite compound Sr2FeMoO6 is considered as an important material for spintronic applications. It appears to be fundamental to understand the role of electronic parameters controlling the half-metallic ground state. Fe-Mo double perovskites usually present some degree of Fe/Mo disorder which generally increases with doping. In this work, we study the valence states of Fe-Mo cations in the off-stoichiometric system Sr2Fe1+xMo1−xO6 (−1 ≤ x ≤ 1/3) with disorder. Our results for Fe and Mo valence states are obtained using the Green functions and the renormalization perturbation expansion method. The model is based on a correlated electron picture with localized Fe-spins and conduction Mo-electrons interacting with the local spins via a double-exchange-type mechanism

  14. Basic features of the pion valence-quark distribution function

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Lei [CSSM, School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005 (Australia); Mezrag, Cédric; Moutarde, Hervé [Centre de Saclay, IRFU/Service de Physique Nucléaire, F-91191 Gif-sur-Yvette (France); Roberts, Craig D. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Rodríguez-Quintero, Jose [Departamento de Física Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, Huelva E-21071 (Spain); Tandy, Peter C. [Center for Nuclear Research, Department of Physics, Kent State University, Kent, OH 44242 (United States)

    2014-10-07

    The impulse-approximation expression used hitherto to define the pion's valence-quark distribution function is flawed because it omits contributions from the gluons which bind quarks into the pion. A corrected leading-order expression produces the model-independent result that quarks dressed via the rainbow–ladder truncation, or any practical analogue, carry all the pion's light-front momentum at a characteristic hadronic scale. Corrections to the leading contribution may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we use an algebraic model to express the principal impact of both classes of corrections. This enables a realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, q{sup π}(x); namely, at a characteristic hadronic scale, q{sup π}(x)∼(1−x){sup 2} for x≳0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum.

  15. Basic features of the pion valence-quark distribution function

    International Nuclear Information System (INIS)

    The impulse-approximation expression used hitherto to define the pion's valence-quark distribution function is flawed because it omits contributions from the gluons which bind quarks into the pion. A corrected leading-order expression produces the model-independent result that quarks dressed via the rainbow–ladder truncation, or any practical analogue, carry all the pion's light-front momentum at a characteristic hadronic scale. Corrections to the leading contribution may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we use an algebraic model to express the principal impact of both classes of corrections. This enables a realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, qπ(x); namely, at a characteristic hadronic scale, qπ(x)∼(1−x)2 for x≳0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum

  16. Low-temperature bonded glass-membrane microfluidic device for in vitro organ-on-a-chip cell culture models

    Science.gov (United States)

    Pocock, Kyall J.; Gao, Xiaofang; Wang, Chenxi; Priest, Craig; Prestidge, Clive A.; Mawatari, Kazuma; Kitamori, Takehiko; Thierry, Benjamin

    2015-12-01

    The integration of microfluidics with living biological systems has paved the way to the exciting concept of "organson- a-chip", which aims at the development of advanced in vitro models that replicate the key features of human organs. Glass based devices have long been utilised in the field of microfluidics but the integration of alternative functional elements within multi-layered glass microdevices, such as polymeric membranes, remains a challenge. To this end, we have extended a previously reported approach for the low-temperature bonding of glass devices that enables the integration of a functional polycarbonate porous membrane. The process was initially developed and optimised on specialty low-temperature bonding equipment (μTAS2001, Bondtech, Japan) and subsequently adapted to more widely accessible hot embosser units (EVG520HE Hot Embosser, EVG, Austria). The key aspect of this method is the use of low temperatures compatible with polymeric membranes. Compared to borosilicate glass bonding (650 °C) and quartz/fused silica bonding (1050 °C) processes, this method maintains the integrity and functionality of the membrane (Tg 150 °C for polycarbonate). Leak tests performed showed no damage or loss of integrity of the membrane for up to 150 hours, indicating sufficient bond strength for long term cell culture. A feasibility study confirmed the growth of dense and functional monolayers of Caco-2 cells within 5 days.

  17. FTIR and molecular mechanics studies of H-bonds in aliphatic polyurethane and polyamide-66 model molecules

    Science.gov (United States)

    Wang, Guoqing; Zhang, Chunxia; Guo, Xiaohe; Ren, Zhiyong

    2008-02-01

    Model aliphatic polyurethane (APU) hard segment based on 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) were prepared. FTIR and molecular mechanics (MM) simulation were used to conduct the systematic studies on APU and polyamide-66 (PA-66) whose sole difference lies in the alkoxyl oxygen. It was found that the introduction of the alkoxyl not only increases the conformations in APU, makes it a possible H-bond acceptor, but also weakens the H-bond between NH and O dbnd C in APU. There are two conformers stably existed in APU with lowest energy, leading to eight H-bond complexes based on NH as donor and (1) O dbnd C as acceptor, and another two complexes based on (2) alkoxyl O and (3) urethane N as acceptors, whereas there is only one stable conformer in PA-66, leading to one H-bond complex. One predominant H-bond complex has been found in APU with probability of about 95%. The simulated results are consistent with the νNH and νC dbnd O band shifting in FTIR.

  18. Nature of the Frequency Shift of Hydrogen Valence Vibrations

    CERN Document Server

    Zhyganiuk, I V

    2015-01-01

    The physical nature of a frequency shift of hydrogen valence vibrations in a water molecule due to its interaction with neighbor molecules has been studied. Electrostatic forces connected with the multipole moments of molecules are supposed to give a dominating contribution to the intermolecular interaction. The frequency shift was calculated in the case where two neighbor molecules form a dimer. The obtained result is in qualitative agreement with the frequency shifts observed for water vapor, hexagonal ice, and liquid water, as well as for aqueous solutions of alcohols. This fact testifies to the electrostatic nature of H-bonds used to describe both the specific features of the intermolecular interaction in water and the macroscopic properties of the latter.

  19. Entanglement convertibility by sweeping through the phase diagram of one dimensional $XXZ$ model with bond alternation

    CERN Document Server

    Tzeng, Yu-Chin; Chung, Ming-Chiang; Amico, Luigi; Kwek, Leong-Chuan

    2016-01-01

    We study the entanglement structure and the topological edge states of the ground state of the spin-1/2 XXZ model with bond alternation. We employ density matrix renormalization group with periodic boundary conditions. The finite-size scaling of R\\'enyi entropies $S_2$ and $S_\\infty$ are used to construct the phase diagram of the system. The phase diagram displays three possible phases: Haldane type (an example of symmetry protected topological ordered phases), dimer and N\\'eel phases, the latter bounded by two continuous quantum phase transitions. The entanglement and non-locality in the ground state are studied by looking at the response of the ground state entanglement to a change of the control parameter. Such a response is quantified by the so called entanglement convertibility. We found that, at small spatial scales, the ground state is not convertible within the topological Haldane dimer phase. The phenomenology we observe can be described in terms of correlations between edge states. We found that the...

  20. Thermal-hydraulic modeling and analysis of spool valve with sloping U-shape notch by bond graph

    Institute of Scientific and Technical Information of China (English)

    娄磊; 吴万荣; 王兆强; 梁向京

    2015-01-01

    To increase the efficiency and reliability of the thermodynamics analysis of the spool valve, the precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke and thermal-hydraulic bond graph based on the conservation of mass and energy were introduced. Subsequently, the connection rule for the bond graph elements and the method to construct the complete thermal-hydraulic system model were proposed. On the basis of heat transfer analysis of a typical hydraulic circuit containing the spool valve, the lumped parameter for mathematical model of the system was given. At last, the reliability of the mathematical model of the flow area and the thermal-hydraulic system for the sloping U-shape notch orifice on the spool were demonstrated by the test. The good agreement between the simulation results and experimental data demonstrates the validity of the modeling method.

  1. Excitations of one-valence-proton, one-valence-neutron nucleus {sup 210}Bi from cold-neutron capture

    Energy Technology Data Exchange (ETDEWEB)

    Cieplicka-Oryńczak, N. [INFN sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków (Poland); Fornal, B.; Szpak, B. [Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków (Poland); Leoni, S.; Bottoni, S. [INFN sezione di Milano, Via Celoria 16, 20133 Milano (Italy); Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Bazzacco, D. [Dipartimento di Fisica e Astronomia dell’Università, I-35131 Padova (Italy); INFN Sezione di Padova, I-35131 Padova (Italy); Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T. [Institute Laue-Langevin, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9 (France); Bocchi, G. [Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); France, G. de [GANIL, Bd. Becquerel, BP 55027, 14076 CAEN Cedex 05 (France); Simpson, G. [LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut National Polytechnique de Grenoble, F-38026 Grenoble Cedex (France); Ur, C. [INFN Sezione di Padova, Via F. Marzolo 8, I-35131 Padova (Italy); Urban, W. [Faculty of Physics, University of Warsaw, ul. Hoża 69, 02-681, Warszawa (Poland)

    2015-10-15

    The low-spin structure of one-proton, one-neutron {sup 210}Bi nucleus was investigated in cold-neutron capture reaction on {sup 209}Bi. The γ-coincidence measurements were performed with use of EXILL array consisted of 16 HPGe detectors. The experimental results were compared to shell-model calculations involving valence particles excitations. The {sup 210}Bi nucleus offers the potential to test the effective proton-neutron interactions because most of the states should arise from the proton-neutron excitations. Additionally, it was discovered that a few states should come from the couplings of valence particles to the 3{sup −} octupole vibration in {sup 208}Pb which provides also the possibility of testing the calculations involving the core excitations.

  2. Excitations of one-valence-proton, one-valence-neutron nucleus 210Bi from cold-neutron capture

    International Nuclear Information System (INIS)

    The low-spin structure of one-proton, one-neutron 210Bi nucleus was investigated in cold-neutron capture reaction on 209Bi. The γ-coincidence measurements were performed with use of EXILL array consisted of 16 HPGe detectors. The experimental results were compared to shell-model calculations involving valence particles excitations. The 210Bi nucleus offers the potential to test the effective proton-neutron interactions because most of the states should arise from the proton-neutron excitations. Additionally, it was discovered that a few states should come from the couplings of valence particles to the 3− octupole vibration in 208Pb which provides also the possibility of testing the calculations involving the core excitations

  3. Particle-phonon excitations in valence-neutron and valence-proton nuclei around 146Gd

    International Nuclear Information System (INIS)

    The present thesis deals with the one-valence-particle nuclei 147Tb and 151Er. The main purpose of the study was, to study characteristic properties of the particle-phonon excitations of these nuclei. In the one-valence-proton nucleus 147Tb from the πh11/2x3- septet only the 15/2+ and 17/2+ Yrast states were known, which underly a strong diagonal exchange interaction. At mass separators in β decay experiments of the 1/2+ and the 11/2-147Dy activities and in in-beam experiments layed out on excitation of states above the Yrast line with 6Li beams the nucleus 147Tb was spectroscoped. The combination of these three data sets made the nearly complete covering of the spin range from 1/2 to 27/2 of the low-lying states in 147Tb possible. At the whole in this nucleus more than 100 hitherto unknown states could be placed and farly characterized. The unusually manifold data allowed to identify beside the complete πh11/2x3- septet also very much further particlexphonon states. Furthermore in the excitation range between 2.5 and 4 MeV numerous three-quasiparticle excitations were observed and in very sufficient way described by parameter-free shell-model calculations. A further important result is the manifestation of a neutron-one-particle-one-hole state with I=27/2, which lies with 3.7 MeV excitation close to the Yrast line. (orig./HSI)

  4. A bond graph model for the sample extraction/injection system of a microsized gas chromatographic instrument

    Science.gov (United States)

    Lin, Jie; Wang, Wanjun; Murphy, Michael C.; Overton, Edward

    1996-09-01

    A bond graph model of the sample extraction/injection system of a prototype portable gas chromatographic instrument has been developed. In addition to performing the same functions as current portable gas chromatographs (GCs), the new generation of GC instruments is designed to perform extraction of analytes from liquid and solid samples. The prototype instrument achieves these improvements by taking of advantage of microfabrication technologies and microprocessor control in the design. A novel sample extraction/injection module is essential to the improved performance of the portable instrument, which will include microfabricated components such as inlets, interface chips, fluid channels, control valves, optimal heater/sensor combinations, and multiport connectors. In order to achieve the desired analytical performance, all of the major components are heated to 250 °C during different stages of a sample analysis. Predicting the performance of the system in this operating regime requires the modeling and analysis of system behavior in two interacting energy domains, fluid and thermal. This article represents the first effort to understand the dynamic behavior of the thermofluid aspect of micro-GC instruments and one of the first attempts to apply the widely-used bond graph technique to modeling and analysis of microsized thermofluid systems. Simulation results using the bond graph model closely match available experimental data, with differences typically less than 10%. This demonstrates that fluid dynamic theory for macroscale systems, and the bond graph method based on it, can be readily applied to microscale systems with these dimensions. The bond graph method can be a useful computer-aided design tool for the development of a new generation of truly integrated micro-GC instruments and sensors fabricated with micromachining technology.

  5. Simulation of cement-improved clay structures with a bonded elasto-plastic model: A practical approach

    OpenAIRE

    Arroyo Alvarez de Toledo, Marcos; Ciantia, M.; Castellanza, Riccardo; Gens Solé, Antonio; NOVA, ROBERTO

    2012-01-01

    Engineering practice has usually dealt with the treated soil bodies using simplistic constitutive models (e.g. elastic perfectly-plastic Mohr–Coulomb). In this paper, a more refined bonded elasto-plastic model is here applied, with emphasis on the ease of calibration. Empirical studies have identified the ratio of cement content to the cured mixture void ratio as a controlling variable for mechanical response. This observation is elaborated upon to show that measuring porosity and unconfined ...

  6. Valence-to-core-detected X-ray absorption spectroscopy

    DEFF Research Database (Denmark)

    Hall, Eleanor R.; Pollock, Christopher J.; Bendix, Jesper;

    2014-01-01

    transitions from filled ligand orbitals to the metal 1s core hole, with distinct energetic shifts for ligands of differing ionization potentials. VtC-detected XAS data were obtained from multiple valence emission features for a series of well-characterized Mn model compounds; taken together, these data...... XAS, nonresonant XES, and VtC RXES data were all modeled within a density functional theory approach. While the TFY XAS and nonresonant XES data are readily interpreted by theory, the VtC RXES cannot be reproduced within such a simplified model. Nonetheless, dramatic changes in the experimental...

  7. Metal-Metal Bonding in Uranium-Group 10 Complexes.

    Science.gov (United States)

    Hlina, Johann A; Pankhurst, James R; Kaltsoyannis, Nikolas; Arnold, Polly L

    2016-03-16

    Heterobimetallic complexes containing short uranium-group 10 metal bonds have been prepared from monometallic IU(IV)(OAr(P)-κ(2)O,P)3 (2) {[Ar(P)O](-) = 2-tert-butyl-4-methyl-6-(diphenylphosphino)phenolate}. The U-M bond in IU(IV)(μ-OAr(P)-1κ(1)O,2κ(1)P)3M(0), M = Ni (3-Ni), Pd (3-Pd), and Pt (3-Pt), has been investigated by experimental and DFT computational methods. Comparisons of 3-Ni with two further U-Ni complexes XU(IV)(μ-OAr(P)-1κ(1)O,2κ(1)P)3Ni(0), X = Me3SiO (4) and F (5), was also possible via iodide substitution. All complexes were characterized by variable-temperature NMR spectroscopy, electrochemistry, and single crystal X-ray diffraction. The U-M bonds are significantly shorter than any other crystallographically characterized d-f-block bimetallic, even though the ligand flexes to allow a variable U-M separation. Excellent agreement is found between the experimental and computed structures for 3-Ni and 3-Pd. Natural population analysis and natural localized molecular orbital (NLMO) compositions indicate that U employs both 5f and 6d orbitals in covalent bonding to a significant extent. Quantum theory of atoms-in-molecules analysis reveals U-M bond critical point properties typical of metallic bonding and a larger delocalization index (bond order) for the less polar U-Ni bond than U-Pd. Electrochemical studies agree with the computational analyses and the X-ray structural data for the U-X adducts 3-Ni, 4, and 5. The data show a trend in uranium-metal bond strength that decreases from 3-Ni down to 3-Pt and suggest that exchanging the iodide for a fluoride strengthens the metal-metal bond. Despite short U-TM (transition metal) distances, four other computational approaches also suggest low U-TM bond orders, reflecting highly transition metal localized valence NLMOs. These are more so for 3-Pd than 3-Ni, consistent with slightly larger U-TM bond orders in the latter. Computational studies of the model systems (PH3)3MU(OH)3I (M = Ni, Pd) reveal

  8. Sketching the pion's valence-quark generalised parton distribution

    Directory of Open Access Journals (Sweden)

    C. Mezrag

    2015-02-01

    Full Text Available In order to learn effectively from measurements of generalised parton distributions (GPDs, it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL truncation of QCD's Dyson–Schwinger equations and exemplified via the pion's valence dressed-quark GPD, Hπv(x,ξ,t. Our analysis focuses primarily on ξ=0, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting Hπv(x,ξ=±1,t with the pion's valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for Hπv(x,0,t, expressed as the Radon transform of a single amplitude. Therewith we obtain results for Hπv(x,0,t and the associated impact-parameter dependent distribution, qπv(x,|b→⊥|, which provide a qualitatively sound picture of the pion's dressed-quark structure at a hadronic scale. We evolve the distributions to a scale ζ=2 GeV, so as to facilitate comparisons in future with results from experiment or other nonperturbative methods.

  9. Sketching the pion's valence-quark generalised parton distribution

    CERN Document Server

    Mezrag, C; Moutarde, H; Roberts, C D; Rodriguez-Quintero, J; Sabatie, F; Schmidt, S M

    2014-01-01

    In order to learn effectively from measurements of generalised parton distributions (GPDs), it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL) truncation of QCD's Dyson-Schwinger equations and exemplified via the pion's valence dressed-quark GPD, $H_\\pi^{\\rm v}(x,\\xi,t)$. Our analysis focuses primarily on $\\xi=0$, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting $H_\\pi^{\\rm v}(x,\\xi=\\pm 1,t)$ with the pion's valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for $H_\\pi^{\\rm v}(x,0,t)$, expressed as th...

  10. Spin-spin critical point correlation functions for the 2D random bond Ising and Potts models

    CERN Document Server

    Dotsenko, V S; Pujol, P; Vladimir Dotsenko; Marco Picco; Pierre Pujol

    1994-01-01

    We compute the combined two and three loop order correction to the spin-spin correlation functions for the 2D Ising and q-states Potts model with random bonds at the critical point. The procedure employed is the renormalisation group approach for the perturbation series around the conformal field theories representing the pure models. We obtain corrections for the correlations functions which produce crossover in the amplitude but don't change the critical exponent in the case of the Ising model and which produce a shift in the critical exponent, due to randomness, in the case of the Potts model. Comparison with numerical data is discussed briefly.

  11. Ab initio modeling of the bonding of benzotriazole corrosion inhibitor to reduced and oxidized copper surfaces.

    Science.gov (United States)

    Kokalj, Anton

    2015-01-01

    The bonding of benzotriazole-an outstanding corrosion inhibitor for copper-on reduced and oxidized copper surfaces is discussed on the basis of density functional theory (DFT) calculations. Calculations reveal that benzotriazole is able to bond with oxide-free and oxidized copper surfaces and on both of them it bonds significantly stronger to coordinatively unsaturated Cu sites. This suggests that benzotriazole is able to passivate the reactive under-coordinated surface sites that are plausible microscopic sites for corrosion attack. Benzotriazole can adsorb in a variety of different forms, yet it forms a strong molecule-surface bond only in deprotonated form. The bonding is even stronger when the deprotonated form is incorporated into organometallic adcomplexes. This is consistent with existing experimental evidence that benzotriazole inhibits corrosion by forming protective organometallic complexes. It is further shown that adsorption of benzotriazole considerably reduces the metal work function, which is a consequence of a large permanent molecular dipole and a properly oriented adsorption structure. It is argued that such a pronounced effect on the work function might be relevant for corrosion inhibition, because it should diminish the anodic corrosion reaction, which is consistent with existing experimental evidence that benzotriazole, although a mixed type inhibitor, predominantly affects the anodic reaction. PMID:25955130

  12. Masked emotional priming beyond global valence activations

    NARCIS (Netherlands)

    M. Rohr; J. Degner; D. Wentura

    2012-01-01

    An immense body of research demonstrates that emotional facial expressions can be processed unconsciously. However, it has been assumed that such processing takes place solely on a global valence-based level, allowing individuals to disentangle positive from negative emotions but not the specific em

  13. Effects of Bond Alternation on the Ground-State Phase Diagram of One-Dimensional XXZ Model

    Institute of Scientific and Technical Information of China (English)

    QIANG Ling; LIU Guang-Hua; TIAN Guang-Shan

    2013-01-01

    The ground-state properties and quantum phase transitions (QPTs) of the one-dimensional bond-alternative XXZ model are investigated by the infinite time-evolving block decimation (iTEBD) method.The bond-alternative effects on its ground-state phase diagram are discussed in detail.Once the bond alternation is taken into account,the antiferromagnetic phase (△ > 1) will be destroyed at a given critical point and change into a disordered phase without nonlocal string order.The QPT is shown to be second-order,and the whole phase diagram is provided.For the ferromagnetic phase region (△ <-1),the critical point rc always equals 1 (independent of △),and the QPT for this case is shown to be first-order.The dimerized Heisenberg model is also discussed,and two disordered phases can be distinguished by with or without nonlocal string orders.Both the bipartite entanglement and the fidelity per site,as two kinds of model-independent measures,are capable of describing all the QPTs in such a quantum model.

  14. The determinants of bond angle variability in protein/peptide backbones: A comprehensive statistical/quantum mechanics analysis.

    Science.gov (United States)

    Improta, Roberto; Vitagliano, Luigi; Esposito, Luciana

    2015-11-01

    The elucidation of the mutual influence between peptide bond geometry and local conformation has important implications for protein structure refinement, validation, and prediction. To gain insights into the structural determinants and the energetic contributions associated with protein/peptide backbone plasticity, we here report an extensive analysis of the variability of the peptide bond angles by combining statistical analyses of protein structures and quantum mechanics calculations on small model peptide systems. Our analyses demonstrate that all the backbone bond angles strongly depend on the peptide conformation and unveil the existence of regular trends as function of ψ and/or φ. The excellent agreement of the quantum mechanics calculations with the statistical surveys of protein structures validates the computational scheme here employed and demonstrates that the valence geometry of protein/peptide backbone is primarily dictated by local interactions. Notably, for the first time we show that the position of the H(α) hydrogen atom, which is an important parameter in NMR structural studies, is also dependent on the local conformation. Most of the trends observed may be satisfactorily explained by invoking steric repulsive interactions; in some specific cases the valence bond variability is also influenced by hydrogen-bond like interactions. Moreover, we can provide a reliable estimate of the energies involved in the interplay between geometry and conformations. PMID:26264789

  15. Chromium valences in ureilite olivine and implications for ureilite petrogenesis

    Science.gov (United States)

    Goodrich, C. A.; Sutton, S. R.; Wirick, S.; Jercinovic, M. J.

    2013-12-01

    Ureilites are a group of ultramafic achondrites commonly thought to be residues of partial melting on a carbon-rich asteroid. They show a large variation in FeO content (olivine Fo values ranging from ∼74 to 95) that cannot be due to igneous fractionation and suggests instead variation in oxidation state. The presence of chromite in only a few of the most ferroan (Fo 75-76) samples appears to support such a model. MicroXANES analyses were used in this study to determine the valence states of Cr (previously unknown) in olivine cores of 11 main group ureilites. The goal of this work was to use a method that is independent of Fo to determine the oxidation conditions under which ureilites formed, in order to evaluate whether the ureilite FeO-variation is correlated with oxidation state, and whether it is nebular or planetary in origin. Two of the analyzed samples, LEW 88774 (Fo 74.2) and NWA 766 (Fo 76.7) contain primary chromite; two others, LAP 03587 (Fo 74.4) and CMS 04048 (Fo 76.2) contain sub-micrometer-sized exsolutions of chromite + Ca-rich pyroxene in olivine; and one, EET 96328 (Fo 85.2) contains an unusual chromite grain of uncertain origin. No chromite has been observed in the remaining six samples (Fo 77.4-92.3). Chromium in olivine in all eleven samples was found to be dominated by the divalent species, with valences ranging from 2.10 ± 0.02 (1σ) to 2.46 ± 0.04. The non-chromite-bearing ureilites have the most reduced Cr, with a weighted mean valence of 2.12 ± 0.01, i.e., Cr2+/Cr3+ = 7.33. All low-Fo chromite-bearing ureilites have more oxidized Cr, with valences ranging from 2.22 ± 0.03 to 2.46 ± 0.04. EET 96328, whose chromite grain we interpret as a late-crystallizing phase, yielded a reduced Cr valence of 2.15 ± 0.07, similar to the non-chromite-bearing samples. Based on the measured Cr valences, magmatic (1200-1300 °C) oxygen fugacities (fO2) of the non-chromite-bearing samples were estimated to be in the range IW-1.9 to IW-2.8 (assuming

  16. An S-N2-model for proton transfer in hydrogen-bonded systems

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2004-01-01

    A new mechanism of proton transfer in donor-acceptor complexes with long hydrogen bonds is suggested. The transition is regarded as totally adiabatic. Two closest water molecules that move synchronously by hindered translation to and from the reaction complex are crucial. The water molecules induce...... a shift of the proton from the donor to the acceptor with simultaneous breaking/formation of hydrogen bonds between these molecules and the proton donor and acceptor. Expressions for the activation barrier and kinetic hydrogen isotope effect are derived. The general scheme is illustrated with the...

  17. Bond order wave (BOW) phase of the extended Hubbard model: Electronic solitons, paramagnetism, coupling to Peierls and Holstein phonons

    OpenAIRE

    Kumar, Manoranjan; Soos, Zolt'an G.

    2011-01-01

    The bond order wave (BOW) phase of the extended Hubbard model (EHM) in one dimension (1D) is characterized at intermediate correlation $U = 4t$ by exact treatment of $N$-site systems. Linear coupling to lattice (Peierls) phonons and molecular (Holstein) vibrations are treated in the adiabatic approximation. The molar magnetic susceptibility $\\chi_M(T)$ is obtained directly up to $N = 10$. The goal is to find the consequences of a doubly degenerate ground state (gs) and finite magnetic gap $E_...

  18. Vibrational properties of the π-bonded chain model of the Si(111) 2 x 1 surface

    International Nuclear Information System (INIS)

    A tight-binding theory is used to study vibrational excitations of the π-bonded chain model of the Si(111)2x1 surface. Some aspects of the surface phonon spectrum are discussed. The authors study the charge fluctuations driven by the vibrational excitations and the surface conductivity associated with the phonons. They find that a longitudinal optical phonon on the surface chains dominates the surface conductivity

  19. Valence atom with bohmian quantum potential: the golden ratio approach

    Directory of Open Access Journals (Sweden)

    Putz Mihai V

    2012-11-01

    Full Text Available Abstract Background The alternative quantum mechanical description of total energy given by Bohmian theory was merged with the concept of the golden ratio and its appearance as the Heisenberg imbalance to provide a new density-based description of the valence atomic state and reactivity charge with the aim of clarifying their features with respect to the so-called DFT ground state and critical charge, respectively. Results The results, based on the so-called double variational algorithm for chemical spaces of reactivity, are fundamental and, among other issues regarding chemical bonding, solve the existing paradox of using a cubic parabola to describe a quadratic charge dependency. Conclusions Overall, the paper provides a qualitative-quantitative explanation of chemical reactivity based on more than half of an electronic pair in bonding, and provide new, more realistic values for the so-called “universal” electronegativity and chemical hardness of atomic systems engaged in reactivity (analogous to the atoms-in-molecules framework.

  20. Bond Markets in Africa

    OpenAIRE

    Yibin Mu; Peter Phelps; Janet Gale Stotsky

    2013-01-01

    African bond markets have been steadily growing in recent years, but nonetheless remain undeveloped. African countries would benefit from greater access to financing and deeper financial markets. This paper compiles a unique set of data on corporate bond markets in Africa. It then applies an econometric model to analyze the key determinants of African government securities market and corporate bond market capitalization. Government securities market capitalization is directly related to bette...

  1. "I Owe Her So Much; Without Her I Would Be Dead": Developing a Model of Mother-Infant Bonding Following a Maternal Antenatal HIV Diagnosis.

    Science.gov (United States)

    Willcocks, Kate; Evangeli, Michael; Anderson, Jane; Zetler, Sarah; Scourse, Rosalind

    2016-01-01

    Women can face a period of psychological vulnerability following antenatal HIV diagnosis, affecting feelings about both the pregnancy and motherhood. Our study explored the impact of being diagnosed with HIV during pregnancy on mother-infant bonding. Grounded Theory was used to assess perceived challenges and facilitating factors for mother-infant bonding for 10 mothers given an HIV diagnosis during pregnancy. Data analysis led to a model of mother-infant bonding composed of four theoretical codes: (a) facing barriers to bonding, (b) feeling disconnected from the baby, (c) developing a special bond, and (d) strengthening and moving on. Challenges with bonding emerged primarily during early stages after diagnosis and birth, with maternal resilience and positivity about the future developing as the infant HIV testing process progressed. Study recommendations include more timely information regarding vertical transmission and more targeted psychological support along with greater promotion of services to support women diagnosed with HIV antenatally. PMID:26382253

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

    OpenAIRE

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

    2015-01-01

    We assess the predictive accuracy of perturbation theory based estimates of changes in covalent bonding due to linear alchemical interpolations among molecules. We have investigated $\\sigma$ bonding to hydrogen, as well as $\\sigma$ and $\\pi$ bonding between main-group elements, occurring in small sets of iso-valence-electronic molecular species with elements drawn from second to fourth rows in the $p$-block of the periodic table. Numerical evidence suggests that first order estimates of coval...

  3. Covalent bonding effect on the mean excitation energy of H2 with the local plasma model

    Science.gov (United States)

    Kamaratos, E.

    1984-01-01

    Chemical bonding is taken into account explicitly in the determination of the mean excitation energy (I) for stopping power of H2 with the local plasma approximation by employing molecular electronic wave functions for H2 for the first time. This procedure leads to a new value for IH2 that is higher than all accepted experimental and theoretical values.

  4. An S-N2-model for proton transfer in hydrogen-bonded systems

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2004-01-01

    A new mechanism of proton transfer in donor-acceptor complexes with long hydrogen bonds is suggested. The transition is regarded as totally adiabatic. Two closest water molecules that move synchronously by hindered translation to and from the reaction complex are crucial. The water molecules indu...

  5. Quantum chemical calculations show that the uranium molecule U2 has a quintuple bond

    OpenAIRE

    Gagliardi, Laura; Roos, Björn O.

    2005-01-01

    Covalent bonding is commonly described by Lewis's theory1, with an electron pair shared between two atoms constituting one full bond. Beginning with the valence bond description2 for the hydrogen molecule, quantum chemists have further explored the fundamental nature of the chemical bond for atoms throughout the periodic table, confirming that most molecules are indeed held together by one electron pair for each bond. But more complex binding may occur when large numbers of atomic orbitals ca...

  6. Chemical bond properties and Mossbauer spectroscopy in (La1-xMx)2CuO4 (M=Ba, Sr)

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By using the average band-gap model, the chemical bond properties of (La1-x Mx)2CuO4(M=Ba, Sr) were calculated . The calculated covalencies for Cu(O and La(O bond in the compounds are 0.3 and 0.03 respectively. M?ssbauer isomer shifts of 57Fe doped in La2CuO4 and 119Sn doped in La2CuO4 were calculated by using the chemical surrounding factor defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57Fe and 119Sn doped La2CuO4.

  7. Torsionally controlled electronic coupling in mixed-valence oxodimolybdenum nitrosyl scorpionates--a DFT study.

    Science.gov (United States)

    Romańczyk, Piotr P; Noga, Klemens; Włodarczyk, Andrzej J; Nitek, Wojciech; Broclawik, Ewa

    2010-09-01

    The density functional theory (DFT) method has been used to study the electronic communication in strongly interacting oxo-bridged di-{Mo(II,I)(NO(+))}(3+,2+) complexes stabilized by tris(3-methylpyrazol-1-yl)borate, [Tp(Me)](-) (dihydroxy 1' and its modified analogs), having fully localized valences on the two Mo centers (Class I), despite a short (ca. 3.8 A) Mo...Mo distance. Structural and electrochemical (separation between the redox potentials Delta(red/ox)E(1/2)) properties and IR spectra (in particular the nu(NO) frequencies) obtained from the B3LYP calculations for 1' are successfully related to experimental values. Strongly twisted geometry with the (O)N-Mo1...Mo2-N(O) angle close to 90 degrees (confirmed by DFT modeling performed for 1'(-1,0,+1) and X-ray diffraction study of [{Mo(NO)(Tp(Me2))(OH)}(2)(mu-O)](-) (1) presented herein) is a common, though so far not fully understood, structural feature of this class of mu-oxo species, in contrast to the closely related {Mo(V)(=O)}(3+) analogs. This study shows that the orthogonality of the local equatorial planes for the two Mo centers may be rationalized by the electronic structure, namely from the balance between the destabilizing repulsion of the Mo-based (d, pi(x)*)(b) electron pairs versus a favorable but relatively weak electron delocalization. Strongly repelling electron pairs avoid each other, which enforces the twisted geometries and blocks the electron delocalization. Steric hindrance (a nonbonding repulsion of the adjacent Tp(x) ligands and the weak hydrogen-bonding interactions, i.e., OH...ON, OH...OH, and C-H...O((NO/OH))) is shown not to be decisive since neither the removal of the inner 3-Me groups of [Tp(Me)](-) in complex 1' nor the substitution of OH groups by OCH(3) ligands did substantially influence the dihedral twist angle in the minimum energy structure. Yet the relative orientation of the {Mo(NO)}(2+,3+) cores along with the position of the bridging oxygen (significantly bent upon

  8. Impact-acoustics inspection of tile-wall bonding integrity via wavelet transform and hidden Markov models

    Science.gov (United States)

    Luk, B. L.; Liu, K. P.; Tong, F.; Man, K. F.

    2010-05-01

    The impact-acoustics method utilizes different information contained in the acoustic signals generated by tapping a structure with a small metal object. It offers a convenient and cost-efficient way to inspect the tile-wall bonding integrity. However, the existence of the surface irregularities will cause abnormal multiple bounces in the practical inspection implementations. The spectral characteristics from those bounces can easily be confused with the signals obtained from different bonding qualities. As a result, it will deteriorate the classic feature-based classification methods based on frequency domain. Another crucial difficulty posed by the implementation is the additive noise existing in the practical environments that may also cause feature mismatch and false judgment. In order to solve this problem, the work described in this paper aims to develop a robust inspection method that applies model-based strategy, and utilizes the wavelet domain features with hidden Markov modeling. It derives a bonding integrity recognition approach with enhanced immunity to surface roughness as well as the environmental noise. With the help of the specially designed artificial sample slabs, experiments have been carried out with impact acoustic signals contaminated by real environmental noises acquired under practical inspection background. The results are compared with those using classic method to demonstrate the effectiveness of the proposed method.

  9. Electron momentum distributions and binding energies for the valence orbitals of hydrogen bromide and hydrogen iodide

    International Nuclear Information System (INIS)

    Electron binding energy spectra and momentum distributions have been obtained for the valence orbitals of HBr and HI using noncoplanar symmetric electron coincidence spectroscopy at 1200 e V. The weakly bonding inner valence ns orbitals, which have not been observed previously, have their spectroscopic (pole) strength severely split among a number of ion states. For HBr the strength of the 'main' inner valence (ns) transition is 0.42 +- 0.03 whereas for HI it is 0.37 +- 0.04, in close agreement with the value observed for the valence s orbitals of the corresponding isoelectronic inert-gas atoms. The spectroscopic strength for the two outermost orbitals is found to be close to unity, in agreement with many-body Green's function calculations. The measured momentum distributions are compared with several spherically averaged MO momentum distributions, as well as (for HBr) with a Green's function calculation of the generalized overlap amplitude (GOA). The GOA momentum distributions are in excellent agreement with the HBr data, both in shape and relative magnitude. Not all of the MO momentum distributions are in reasonable agreement with the data. Comparison is also made with the calculated momentum distributions for Kr, Br, Xe and I. (orig.)

  10. Electron momentum distributions and binding energies for the valence orbitals of hydrogen bromide and hydrogen iodide

    International Nuclear Information System (INIS)

    The electron binding energy spectra and momentum distributions have been obtained for the valence orbitals of HBr and HI using noncoplanar symmetric electron coincidence spectroscopy at 1200eV. The weakly bonding inner valence ns orbitals, which have not been previously observed, have their spectroscopic (pole) strength severely split among a number of ion states. For HBr the strength of the main inner valence (ns) transition is 0.42 0.03 whereas for HI it is 0.37 0.04, in close agreement with that observed for the valence s orbitals of the corresponding isoelectronic inert gas atoms. The spectroscopic strength for the two outermost orbitals is found to be close to unity, in agreement with many body Green's function calculations. The measured momentum distributions are compared with several spherically averaged MO momentum distributions, as well as (for HBr) with a Green's function calculation of the generalized overlap amplitude (GOA). The GOA momentum distributions are in excellent agreement with the HBr data, both in shape and relative magnitude. Not all of the MO momentum distributions are in reasonable agreement with the data. Comparison is also made with the calculated momentum distributions for Kr, Br, Xe and I

  11. Slave-boson approach to the size-dependent transition from van der Waals to covalent bonding in Hg_n clusters

    OpenAIRE

    Garcia, Martin E.; Bennemann, K. H.

    1994-01-01

    We use a microscopic theory to describe the dynamics of the valence electrons in divalent-metal clusters. The theory is based on a many-body model Harniltonian H which takes into account, on the same electronic level, the van der Waals and the covalent bonding. In order to study the ground-state properties of H we have developed an extended slave-boson method. We have studied the bonding character and the degree of electronic delocalization in Hg_n clusters as a function of cluste...

  12. Probabilistic modeling of shear-induced formation and breakage of doublets cross-linked by receptor-ligand bonds.

    OpenAIRE

    Long, M.; Goldsmith, H L; Tees, D. F.; C. Zhu

    1999-01-01

    A model was constructed to describe previously published experiments of shear-induced formation and breakage of doublets of red cells and of latexes cross-linked by receptor-ligand bonds (. Biophys. J. 65:1318-1334; Tees and Goldsmith. 1996. Biophys. J. 71:1102-1114;. Biophys. J. 71:1115-1122). The model, based on McQuarrie's master equations (1963. J. Phys. Chem. 38:433-436), provides unifying treatments for three distinctive time periods in the experiments of particles in a Couette flow in ...

  13. Evaluation of bond strength of silorane and methacrylate based restorative systems to dentin using different cavity models

    Directory of Open Access Journals (Sweden)

    Stephano Zerlottini Isaac

    2013-09-01

    Full Text Available OBJECTIVE: The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS to dentin of two different restorative systems: silorane-based (P90, and methacrylate-based (P60, using two cavity models. MATERIAL AND METHODS: Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5 were prepared in 20 teeth, which were divided into two groups (n=10 restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer's instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2 and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10. The teeth were sectioned into samples with area between 0.85 and 1.25 mm2 that were submitted to µTBS testing, using a universal testing machine (EMIC at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests. RESULTS: For flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p0.05, or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>0.05. Regarding fracture pattern, there was no statistical difference among groups (p=0.0713 and 56.3% of the fractures were adhesive. CONCLUSION: It was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor.

  14. Money and Nominal Bonds

    OpenAIRE

    Marchesiani, Alessandro; Senesi, Pietro

    2007-01-01

    This paper studies an economy with trading frictions, ex post heterogeneity and nominal bonds in a model à la Lagos and Wright (2005). It is shown that a strictly positive interest rate is a sufficient condition for the allocation with nominal bonds to be welfare improving. This result comes from the protection against the inflation tax.

  15. Hydrogen bonding in polyanilines

    Energy Technology Data Exchange (ETDEWEB)

    Bahceci, S. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Toppare, L. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Yurtsever, E. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey))

    1994-11-29

    Hydrogen bonding between poly(bisphenol A carbonate) (PC) and polyaniline (PAn) is analyzed using semi-empirical quantum methodology. Fully optimized AM1 molecular orbital calculations are reported for various aniline structures (monomer, dimer and trimer), the monomer of the PC and the hydrogen-bonded model of PAn-PC oligomer. ((orig.))

  16. Neutron inelastic scattering from mixed valence materials

    International Nuclear Information System (INIS)

    Paramagnetic scattering from mixed valence materials is reviewed. Some of the early measurements identified a broad quasielastic spectral distribution (e.g. a Lorentzian centered on zero energy with large, practically Q-independent widths (half-width approx.5-30 MeV) which remain finite as T → OK. More recent measurements using high energy neutrons on several mixed valance systems reveal inelastic peaks superposed on the broad quasielastic spectrum at low temperatures. These inelastic peaks progressively melt away with increasing temperature, accompanied possibly by some softening, and disappear almost completely around the temperature of the maximum in the susceptibility. Several possible mechanisms could semi-qualitatively account for the observed spectral response, a deeper insight into whose origin would aid in understanding the mixed valence phenomena

  17. Evaluative conditioning induces changes in sound valence

    Directory of Open Access Journals (Sweden)

    Anna C. Bolders

    2012-04-01

    Full Text Available Evaluative Conditioning (EC has hardly been tested in the auditory domain, but it is a potentially valuable research tool. In Experiment 1 we investigated whether the affective evaluation of short environmental sounds can be changed using affective words as unconditioned stimuli (US. Congruence effects on an affective priming task (APT for conditioned sounds demonstrated successful EC. Subjective ratings for sounds paired with negative words changed accordingly. In Experiment 2 we investigated whether the acquired valence remains stable after repeated presentation of the conditioned sound without the US or whether extinction occurs. The acquired affective value remained present, albeit weaker, even after 40 extinction trials. These results warrant the use of EC to study processing of short environmental sounds with acquired valence, even if this requires repeated stimulus presentations. This paves the way for studying processing of affective environmental sounds while effectively controlling low level-stimulus properties.

  18. Atomistic modeling of amorphous silicon carbide using a bond-order potential

    International Nuclear Information System (INIS)

    Molecular dynamics simulations were performed with a Brenner-type bond-order potential to study the melting of silicon carbide (SiC), the structure of amorphous SiC produced by quenching from the melt, and the evolution of the amorphous state after isochronal annealing at elevated temperatures. The simulations reveal that SiC melts above 3700 K with an enthalpy of fusion of about 0.6 eV/atom. The density of the quenched liquid is about 2820 kg/m3, in excellent agreement with the experimental value for SiC amorphized by neutron irradiation. In addition to the loss of long-range order, the quenched liquid shows short-range disorder as measured by the C homonuclear bond ratio. Upon annealing, there is partial recovery of short-range order

  19. Electron magnetic scattering on valence nucleon orbits

    International Nuclear Information System (INIS)

    Cross-sections for elastic electron scattering by the magnetization distribution of 49Ti, 51V, 59Co, 87Sr and 93Nb have been measured in the range of momentum transfer 1.7 - 3.3 fm-1. The results are interpreted in terms of radial distribution of the unpaired proton or neutron. Meson exchange and core polarisation effects are investigated. The valence nucleon radii obtained are compared with Hartree-Fock predictions

  20. Effects of valence in decision making

    OpenAIRE

    Noh, Zamira; Goddard, Paul

    2014-01-01

    Background/Aim:- A study of voting decisions in The Weakest Link TV game show has shown the contestants tend to avoid their nearest neighbours (Goddard, Hylton, Parke & Noh, 2013), presumably this is because the vote carries negative connotations. Therefore, the aim of this study was to test whether vote valence affects voting behaviour in other voting scenarios. Procedure:- Participants were undergraduate Psychology students (n=233) attending an orientation lecture during their first inducti...

  1. Analytical modeling of mixed-Mode bending behavior of asymmetric adhesively bonded pultruded GFRP joints

    Czech Academy of Sciences Publication Activity Database

    Ševčík, Martin; Shahverdi, M.; Hutař, Pavel; Vassilopoulos, Anastasios P.

    2015-01-01

    Roč. 147, OCT (2015), s. 228-242. ISSN 0013-7944 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068; GA MŠk(CZ) EE2.3.30.0063 Institutional support: RVO:68081723 Keywords : Mixed-Mode delamination * Asymmetric joint * Adhesively bonded joint * Failure criterion * Analytical prediction * GFRP Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.767, year: 2014

  2. Strength Modeling of Reinforced Concrete Beam with Externally Bonded FRP Reinforcement

    OpenAIRE

    N. Pannirselvam; P. N. Ragunath; Suguna, K

    2008-01-01

    This research study presents the evaluation of the structural behaviour of reinforced concrete beams with externally bonded Fibre Reinforced Polymer (FRP) reinforcements. Three different steel ratios with two different Glass Fibre Reinforced Polymer (GFRP) types and two different thicknesses in each type of GFRP were used. Totally fifteen rectangular beams of 3 m length were cast. Three rectangular beams were used as reference beam (Control Beams) and the remaining were fixed with GFRP lamina...

  3. 5th International Conference on Valence Fluctuations

    CERN Document Server

    Malik, S

    1987-01-01

    During the Koln meeting (August 28-31, 1984), Irdia was chosen as the venue for the next International Conference on Valence Fluctuations. lhis was in recognition ard appreciation of the work done, both experimental ard theoretical, by the Irdian scientists in this area during the last decade. We decided to hold this Conference in the month of January, 1987 at Bangalore. lhe subject of Valence Fluctuations has kept itself alive ard active as it has provided many shocks ard suprises particularly among the Ce- ard U-based intermetallies. lhe richness of many interesting physical phenomena occurring in mixed valent materials, the flexibility of modifying their physical properties (by alloying, for example) ard the possibility of synthesizing a wide variety of new such materials seem to be the key factors in this regard. Barely six months before this Conference, an International Conference on Anomalous Rare Earths and Actinides (ICAREA) had been held at Grenoble (July, 1986) which also focussed on mixed valence a...

  4. Valuation of Indonesian catastrophic earthquake bonds with generalized extreme value (GEV) distribution and Cox-Ingersoll-Ross (CIR) interest rate model

    Science.gov (United States)

    Gunardi, Setiawan, Ezra Putranda

    2015-12-01

    Indonesia is a country with high risk of earthquake, because of its position in the border of earth's tectonic plate. An earthquake could raise very high amount of damage, loss, and other economic impacts. So, Indonesia needs a mechanism for transferring the risk of earthquake from the government or the (reinsurance) company, as it could collect enough money for implementing the rehabilitation and reconstruction program. One of the mechanisms is by issuing catastrophe bond, `act-of-God bond', or simply CAT bond. A catastrophe bond issued by a special-purpose-vehicle (SPV) company, and then sold to the investor. The revenue from this transaction is joined with the money (premium) from the sponsor company and then invested in other product. If a catastrophe happened before the time-of-maturity, cash flow from the SPV to the investor will discounted or stopped, and the cash flow is paid to the sponsor company to compensate their loss because of this catastrophe event. When we consider the earthquake only, the amount of discounted cash flow could determine based on the earthquake's magnitude. A case study with Indonesian earthquake magnitude data show that the probability of maximum magnitude can model by generalized extreme value (GEV) distribution. In pricing this catastrophe bond, we assumed stochastic interest rate that following the Cox-Ingersoll-Ross (CIR) interest rate model. We develop formulas for pricing three types of catastrophe bond, namely zero coupon bonds, `coupon only at risk' bond, and `principal and coupon at risk' bond. Relationship between price of the catastrophe bond and CIR model's parameter, GEV's parameter, percentage of coupon, and discounted cash flow rule then explained via Monte Carlo simulation.

  5. Bond lengths and bond strengths in compounds of the 5f elements

    International Nuclear Information System (INIS)

    The variation of bond length (D) with bond strength (S) in normal valence compounds of 3d, 4d, 5d-4f, and 6d-5f elements can be represented approximately as D(S)=D(0.5) F(S), where D(0.5) is a characteristic constant for a given bond and F(S) an empirical function which is the same for all bonds. A bond strength Ssub(ij)=Ssub(ji) is assigned to the bond between atoms i and j such that Σsub(j)Ssub(ij)=Vsub(i) and Σsub(i)Ssub(ij)=Vsub(j), where Vsub(i) and Vsub(j) are the normal valences of the two atoms. The function F(S) decreases monotonically with increasing S, and is normalized to unity at S=0.5, so that the constant D(0.5) has the physical meaning of being the bond length adjusted to S=0.5. In this paper, this method of interpretation is used to interpret and systematize the experimental results on bond lengths in oxides, halides and oxy-halides of the 5f elements. (Auth.)

  6. The method of thermodynamic perturbation in the intermediate valence problem

    International Nuclear Information System (INIS)

    The effect of hybridization on the free energy and the magnetic susceptibility X of intermediate valence compounds is studied employing the method of thermodynamic perturbation in second order. This method is applied to a lattice with a variable concentration c of impurities that are described by the Anderson model. A non-divergent logarithmic correction appears when the chemical potential μ sub(e) is not in the middle of the rectangular conduction band, and it is shown by a different method that this correction is also present in the exactly soluble case of independent electrons with hybridization. When c=1 the logarithmic term is cancelled by a term proportional to (δ2μ sub(e)/δH2). By thermodynamic arguments it is shown that this concentration dependent contribution coincides with a different expression that was recently obtained by another approach. The contribution of the third state of charge to X is discussed; this state is usually neglected in intermediate valence models. (Author)

  7. Supertoughening in B1 transition metal nitride alloys by increased valence electron concentration

    Energy Technology Data Exchange (ETDEWEB)

    Sangiovanni, D.G., E-mail: davsan@ifm.liu.se [Thin Film Physics, Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Hultman, L.; Chirita, V. [Thin Film Physics, Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden)

    2011-03-15

    We use density functional theory calculations to explore the effects of alloying cubic TiN and VN with transition metals M = Nb, Ta, Mo or W at 50% concentrations. The ternary systems obtained are predicted to be supertough, as they are shown to be harder and significantly more ductile compared with reference binary systems. The primary electronic mechanism of this supertoughening effect is shown in a comprehensive electronic structure analysis of these compounds to be the increased valence electron concentration intrinsic to these ternary systems. Our investigations reveal the complex nature of chemical bonding in these compounds, which ultimately explains the observed selective response to stress. The findings presented in this paper thus offer a design route for the synthesis of supertough transition metal nitride alloys via valence electron concentration tuning.

  8. Supertoughening in B1 transition metal nitride alloys by increased valence electron concentration

    International Nuclear Information System (INIS)

    We use density functional theory calculations to explore the effects of alloying cubic TiN and VN with transition metals M = Nb, Ta, Mo or W at 50% concentrations. The ternary systems obtained are predicted to be supertough, as they are shown to be harder and significantly more ductile compared with reference binary systems. The primary electronic mechanism of this supertoughening effect is shown in a comprehensive electronic structure analysis of these compounds to be the increased valence electron concentration intrinsic to these ternary systems. Our investigations reveal the complex nature of chemical bonding in these compounds, which ultimately explains the observed selective response to stress. The findings presented in this paper thus offer a design route for the synthesis of supertough transition metal nitride alloys via valence electron concentration tuning.

  9. Mechanism of gold solvent extraction from aurocyanide solution by quaternary amines: models of extracting species based on hydrogen bonding

    Institute of Scientific and Technical Information of China (English)

    马刚; 闫文飞; 陈景; 严纯华; 高宏成; 周维金; 施鼐; 吴谨光; 徐光宪; 黄昆; 余建民; 崔宁

    2000-01-01

    The mechanism of gold solvent extraction from KAu(CN)2 solution was investigated by means of FTIR, EXAFS, ICP and radioactive tracer methods. Two extraction systems were studied, namely N263-tributyl phosphate(TBP)-n-dodecane and N263-iso-octanol-n-dodecane. High-resolution FT IR spectroscopy indicated that the CN stretching vibrations of the two extraction systems differred greatly. In order to interpret the significant difference in CN stretching vibrations, twoextracting species models are proposed——supramolecular structures based on the formation ofhydrogen bonds between Au(CN)2- and modifiers such as TBP and iso-octanol.

  10. Evaluation of bond strength of silorane and methacrylate based restorative systems to dentin using different cavity models

    OpenAIRE

    Stephano Zerlottini Isaac; Ana Claudia Pietrobom Bergamin; Cecilia Pedroso Turssi; Flavia Lucisano Botelho do Amaral; Roberta Tarkany Basting; Fabiana Mantovani Gomes Franca

    2013-01-01

    OBJECTIVE: The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) to dentin of two different restorative systems: silorane-based (P90), and methacrylate-based (P60), using two cavity models. MATERIAL AND METHODS: Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5) were prepared in 20 teeth, which were divided into two groups (n...

  11. Mechanism of gold solvent extraction from aurocyanide solution by quaternary amines: models of extracting species based on hydrogen bonding

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The mechanism of gold solvent extraction from KAu(CN)2 solution was investigated by means of FTIR, EXAFS, ICP and radioactive tracer methods. Two extraction systems were studied, namely N263-tributyl phosphate(TBP)-n-dodecane and N263-iso-octanol-n-dodecane. High-reso- lution FT IR spectroscopy indicated that the CN stretching vibrations of the two extraction systems differred greatly. In order to interpret the significant difference in CN stretching vibrations, two extracting species models are proposed supramolecular structures based on the formation of hydrogen bonds between Au(CN)2- and modifiers such as TBP and iso-octanol.

  12. Valence electronic structure of CH3F and CH3Cl: electron momentum distributions and separation energies

    International Nuclear Information System (INIS)

    Fluoromethane (CH3F) has been studied by binary (e,2e) coincidence spectroscopy at 1200 eV using non-coplanar symmetric kinematics. Separation energy spectra have been determined in the energy range up to 50 eV at azimuthal angles of 0 degrees and 9 degrees. The separation energy spectra and electron momentum distributions measured for the valence orbitals of CH3F and CH3Cl are compared with the results of calculations employing SCF wavefunctions outer valence as well as extended 2ph-TDA Green's function methods. Electron density and momentum density maps have been generated for all valence orbitals of both molecules. using the SCF wavefunctions and are used to explain differences in the bonding properties of the halomethanes investigated here

  13. Electron spectroscopy of valence and core states of U intermetallic compounds

    International Nuclear Information System (INIS)

    Examples of valence and core level spectra of uranium intermetallic compounds are analyzed using different theoretical models. The shortcomings of the different approximations are discussed and it is pointed out how these models have to be extended for a realistic description of U compounds. (orig.)

  14. The structure and bonding of iron-acceptor pairs in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, S.; Assali, L.V.C.; Kimerling, L.C. [Massachusetts Inst. of Technology, Cambridge, MA (United States)

    1995-08-01

    The highly mobile interstitial iron and Group III impurities (B, Al, Ga, In) form iron-acceptor pairs in silicon. Based on the migration kinetics and taking host silicon as a dielectric medium, we have simulated the pairing process in a static silicon lattice. Different from the conventional point charge ionic model, our phenomenological calculations include (1) a correction that takes into account valence electron cloud polarization which adds a short range, attractive interaction in the iron-acceptor pair bonding; and (2) silicon lattice relaxation due to the atomic size difference which causes a local strain field. Our model explains qualitatively (1) trends among the iron-acceptor pairs revealing an increase of the electronic state hole emission energy with increasing principal quantum number of acceptor and decreasing pair separation distance; and (2) the stable and metastable sites and configurational symmetries of the iron-acceptor pairs. The iron-acceptor pairing and bonding mechanism is also discussed.

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

    Science.gov (United States)

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

    2010-01-01

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

  16. Chemical bonding in copper-based transparent conducting oxides: CuMO(2) (M = In, Ga, Sc)

    OpenAIRE

    Scanlon, David; ALLEN, JEREMY; WATSON, GRAEME WILLIAM; GODINHO, KATHERINE GITANJALI

    2011-01-01

    PUBLISHED The geometry and electronic structure of copper-based p-type delafossite transparent conducting oxides, CuMO(2) (M = In, Ga, Sc), are studied using the generalized gradient approximation (GGA) corrected for on-site Coulomb interactions (GGA + U). The bonding and valence band compositions of these materials are investigated, and the origins of changes in the valence band features between group 3 and group 13 cations are discussed. Analysis of the effective masses at the valence an...

  17. Curly arrows meet electron density transfers in chemical reaction mechanisms: from electron localization function (ELF) analysis to valence-shell electron-pair repulsion (VSEPR) inspired interpretation.

    Science.gov (United States)

    Andrés, Juan; Berski, Sławomir; Silvi, Bernard

    2016-07-01

    Probing the electron density transfers during a chemical reaction can provide important insights, making possible to understand and control chemical reactions. This aim has required extensions of the relationships between the traditional chemical concepts and the quantum mechanical ones. The present work examines the detailed chemical insights that have been generated through 100 years of work worldwide on G. N. Lewis's ground breaking paper on The Atom and the Molecule (Lewis, G. N. The Atom and the Molecule, J. Am. Chem. Soc. 1916, 38, 762-785), with a focus on how the determination of reaction mechanisms can be reached applying the bonding evolution theory (BET), emphasizing how curly arrows meet electron density transfers in chemical reaction mechanisms and how the Lewis structure can be recovered. BET that combines the topological analysis of the electron localization function (ELF) and Thom's catastrophe theory (CT) provides a powerful tool providing insight into molecular mechanisms of chemical rearrangements. In agreement with physical laws and quantum theoretical insights, BET can be considered as an appropriate tool to tackle chemical reactivity with a wide range of possible applications. Likewise, the present approach retrieves the classical curly arrows used to describe the rearrangements of chemical bonds for a given reaction mechanism, providing detailed physical grounds for this type of representation. The ideas underlying the valence-shell-electron pair-repulsion (VSEPR) model applied to non-equilibrium geometries provide simple chemical explanations of density transfers. For a given geometry around a central atom, the arrangement of the electronic domain may comply or not with the VSEPR rules according with the valence shell population of the considered atom. A deformation yields arrangements which are either VSEPR defective (at least a domain is missing to match the VSEPR arrangement corresponding to the geometry of the ligands), VSEPR compliant

  18. Valence of 'divalent' rare earth metals

    International Nuclear Information System (INIS)

    It is generally recognized that light rare earths change their valence from 2 to 3 when forming a bulk metal while remaining divalent at the surface. However, performed DFT calculations ultimately indicate that the higher-binding-energy peaks in photoemission spectra (like the -5.3 eV peak for Sm), characteristic of the trivalent 4fn-15d1 configuration, correspond not to the ground state, but to excited states induced by radiation. This means that the trivalent state is not inherent for the bulk of divalent rare earths, and therefore they do not become trivalent.

  19. Hamiltonian formulation of bond graphs

    NARCIS (Netherlands)

    Golo, Goran; Schaft, van der Arjan; Breedveld, Peter C.; Maschke, Bernhard M.; Johansson, R.; Rantzer, A.

    2003-01-01

    This paper deals with the 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 the equations describing a bond graph model correspond to a port Hamiltonian system. The conditions

  20. Cerium valence change in the solid solutions Ce(Rh1-xRux)Sn

    International Nuclear Information System (INIS)

    The solid solutions Ce(Rh1-xRux)Sn were investigated by means of susceptibility measurements, specific heat, electrical resistivity, X-ray absorption spectroscopy (XAS), and 119Sn Moessbauer spectroscopy. Magnetic measurements as well as XAS data show a cerium valence change in dependence on the ruthenium content. Higher ruthenium content causes an increase from 3.22 to 3.45 at 300 K. Furthermore χ and χ-1 data indicate valence fluctuation for cerium as a function of temperature. For example, Ce(Rh0.8Ru0.2)Sn exhibits valence fluctuations between 3.42 and 3.32 in the temperature range of 10 to 300 K. This could be proven by using the interconfiguration fluctuation (ICF) model introduced by Sales and Wohlleben. Cerium valence change does not influence the tin atoms as proven by 119Sn Moessbauer spectroscopy, but it influences the electrical properties. Ce(Rh0.9Ru0.1)Sn behaves like a typical valence fluctuating compound, and higher ruthenium content causes an increase of the metallic behavior. (orig.)

  1. Pricing convertible bonds based on a multi-stage compound-option model

    Science.gov (United States)

    Gong, Pu; He, Zhiwei; Zhu, Song-Ping

    2006-07-01

    In this paper, we introduce the concept of multi-stage compound options to the valuation of convertible bonds (CBs). Rather than evaluating a nested high-dimensional integral that has arisen from the valuation of multi-stage compound options, we found that adopting the finite difference method (FDM) to solve the Black-Scholes equation for each stage actually resulted in a better numerical efficiency. By comparing our results with those obtained by solving the Black-Scholes equation directly, we can show that the new approach does provide an approximation approach for the valuation of CBs and demonstrate that it offers a great potential for a further extension to CBs with more complex structures such as those with call and/or put provisions.

  2. Simulating Valence-to-Core X-ray Emission Spectroscopy of Transition Metal Complexes with Time-Dependent Density Functional Theory

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yu; Mukamel, Shaul; Khalil, Munira; Govind, Niranjan

    2015-11-09

    Valence-to-core (VtC) X-ray emission spectroscopy (XES) has emerged as a power- ful technique for the structural characterization of complex organometallic compounds in realistic environments. Since the spectrum represents electronic transitions from the ligand molecular orbitals to the core holes of the metal centers, the approach is more chemically sensitive to the metal-ligand bonding character compared with con- ventional X-ray absorption techniques. In this paper we study how linear-response time-dependent density functional theory (LR-TDDFT) can be harnessed to simulate K-edge VtC X-ray emission spectra reliably. LR-TDDFT allows one to go beyond the single-particle picture that has been extensively used to simulate VtC-XES. We con- sider seven low- and high-spin model complexes involving chromium, manganese and iron transition metal centers. Our results are in good agreement with experiment.

  3. NATO Advanced Study Institute on Mixed-Valence Compounds : Theory and Applications in Chemistry, Physics, Geology, and Biology

    CERN Document Server

    1980-01-01

    It has been a decade since two seminal reviews demonstrated that mixed-valence compounds share many unique and fascinating features. The insight pro­ vided by those early works has promoted a great deal of both experimental and theoretical study. As a result of extensive efforts, our understanding of the bonding and properties of mixed-valence compounds has advanced substantially. There has been no compre­ hensive treatment of mixed-valence compounds since 1967, and the meeting convened at Oxford in September, 1979, provided a unique opportunity to examine the subject and its many ramifications. Mixed-valence compounds play an important role in many fields. Although the major impact of the subject has been in chemistry, its importance has become increasingly clear in solid state physics, geology, and biology. Extensive interest and effort in the field of molecular metals has demonstrated that mixed-valency is a prerequisite for high elec­ trical conductivity. The intense colors of many minerals have been s...

  4. Accounting for the differences in the structures and relative energies of the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I4 2+, the Se-I pi-bonded Se2I4 2+, and their higher-energy isomers by AIM, MO, NBO, and VB methodologies.

    Science.gov (United States)

    Brownridge, Scott; Crawford, Margaret-Jane; Du, Hongbin; Harcourt, Richard D; Knapp, Carsten; Laitinen, Risto S; Passmore, Jack; Rautiainen, J Mikko; Suontamo, Reijo J; Valkonen, Jussi

    2007-02-01

    The bonding in the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I42+ (three sigma + two pi bonds), the Se-I pi-bonded Se2I42+ (four sigma + one pi bonds), and their higher-energy isomers have been studied using modern DFT and ab initio calculations and theoretical analysis methods: atoms in molecules (AIM), molecular orbital (MO), natural bond orbital (NBO), and valence bond (VB) analyses, giving their relative energies, theoretical bond orders, and atomic charges. The aim of this work was to seek theory-based answers to four main questions: (1) Are the previously proposed simple pi*-pi* bonding models valid for S2I42+ and Se2I42+? (2) What accounts for the difference in the structures of S2I42+ and Se2I42+? (3) Why are the classically bonded isolobal P2I4 and As2I4 structures not adopted? (4) Is the high experimentally observed S-S bond order supported by theoretical bond orders, and how does it relate to high bond orders between other heavier main group elements? The AIM analysis confirmed the high bond orders and established that the weak bonds observed in S2I42+ and Se2I42+ are real and the bonding in these cations is covalent in nature. The full MO analysis confirmed that S2I42+ contains three sigma and two pi bonds, that the positive charge is essentially equally distributed over all atoms, that the bonding between S2 and two I2+ units in S2I42+ is best described by two mutually perpendicular 4c2e pi*-pi* bonds, and that in Se2I42+, two SeI2+ moieties are joined by a 6c2e pi*-pi* bond, both in agreement with previously suggested models. The VB treatment provided a complementary approach to MO analysis and provided insight how the formation of the weak bonds affects the other bonds. The NBO analysis and the calculated AIM charges showed that the minimization of the electrostatic repulsion between EI2+ units (E = S, Se) and the delocalization of the positive charge are the main factors that explain why the nonclassical structures are favored for S2I42

  5. Tetra-bonding of C, N and O at solid surface

    OpenAIRE

    Sun, Chang Q.

    2008-01-01

    In order to gain advanced understanding of the kinetics and dynamics of C, N, and O reacting with a solid surface, it is necessary to consider the reaction from the perspectives of bond formation, bond dissociation, bond relaxation, bond vibration, and the associated charge redistribution and polarization and the energetic response of the involved atoms and valence electrons. The sp-orbital hybridization is found necessary for these concerned reactions associated with strongly anisotropic bon...

  6. Neutron scattering on intermediate valence systems

    International Nuclear Information System (INIS)

    The temperature dependence of the magnetic relaxation line widths (quasielastic (QE) line widths) and the crystal field excitations of some novel intermediate valent systems were measured by means of inelastic neutron scattering. Some striking new features of the alloys YbBe13, YbPd and Yb3Pd4 appoint them to belong to a new type of intermediate valent systems. YbAl3 shows several inelastic lines, but no QE-line was measurable. The heavy fermion systems CeCu6 and URu2Si2 show a strongly temperature dependent QE-line width, in course of which CeCu6 tends towards a nonvanishing residual value for T->0, which matches with theoretical predictions. For the first time valence instabilities of Pr (PrPd) and Sm (Smsub(0.51)Ysub(0.49)Al2) could be prooved by neutron scattering. In addition to these experiments, in YbCu2Si2 and TmTe the shifts in valency, caused by external hydrostatic pressure, were studied with a pressure cell for neutron scattering, especially designed and constructed for these special purposes. The corresponding observed changes of the QE-line widths coincide with the expected values, both in sign and absolute value. (orig.)

  7. Valuation of Indonesian catastrophic earthquake bonds with generalized extreme value (GEV) distribution and Cox-Ingersoll-Ross (CIR) interest rate model

    Energy Technology Data Exchange (ETDEWEB)

    Gunardi,; Setiawan, Ezra Putranda [Mathematics Department, Gadjah Mada University (Indonesia)

    2015-12-22

    Indonesia is a country with high risk of earthquake, because of its position in the border of earth’s tectonic plate. An earthquake could raise very high amount of damage, loss, and other economic impacts. So, Indonesia needs a mechanism for transferring the risk of earthquake from the government or the (reinsurance) company, as it could collect enough money for implementing the rehabilitation and reconstruction program. One of the mechanisms is by issuing catastrophe bond, ‘act-of-God bond’, or simply CAT bond. A catastrophe bond issued by a special-purpose-vehicle (SPV) company, and then sold to the investor. The revenue from this transaction is joined with the money (premium) from the sponsor company and then invested in other product. If a catastrophe happened before the time-of-maturity, cash flow from the SPV to the investor will discounted or stopped, and the cash flow is paid to the sponsor company to compensate their loss because of this catastrophe event. When we consider the earthquake only, the amount of discounted cash flow could determine based on the earthquake’s magnitude. A case study with Indonesian earthquake magnitude data show that the probability of maximum magnitude can model by generalized extreme value (GEV) distribution. In pricing this catastrophe bond, we assumed stochastic interest rate that following the Cox-Ingersoll-Ross (CIR) interest rate model. We develop formulas for pricing three types of catastrophe bond, namely zero coupon bonds, ‘coupon only at risk’ bond, and ‘principal and coupon at risk’ bond. Relationship between price of the catastrophe bond and CIR model’s parameter, GEV’s parameter, percentage of coupon, and discounted cash flow rule then explained via Monte Carlo simulation.

  8. Valuation of Indonesian catastrophic earthquake bonds with generalized extreme value (GEV) distribution and Cox-Ingersoll-Ross (CIR) interest rate model

    International Nuclear Information System (INIS)

    Indonesia is a country with high risk of earthquake, because of its position in the border of earth’s tectonic plate. An earthquake could raise very high amount of damage, loss, and other economic impacts. So, Indonesia needs a mechanism for transferring the risk of earthquake from the government or the (reinsurance) company, as it could collect enough money for implementing the rehabilitation and reconstruction program. One of the mechanisms is by issuing catastrophe bond, ‘act-of-God bond’, or simply CAT bond. A catastrophe bond issued by a special-purpose-vehicle (SPV) company, and then sold to the investor. The revenue from this transaction is joined with the money (premium) from the sponsor company and then invested in other product. If a catastrophe happened before the time-of-maturity, cash flow from the SPV to the investor will discounted or stopped, and the cash flow is paid to the sponsor company to compensate their loss because of this catastrophe event. When we consider the earthquake only, the amount of discounted cash flow could determine based on the earthquake’s magnitude. A case study with Indonesian earthquake magnitude data show that the probability of maximum magnitude can model by generalized extreme value (GEV) distribution. In pricing this catastrophe bond, we assumed stochastic interest rate that following the Cox-Ingersoll-Ross (CIR) interest rate model. We develop formulas for pricing three types of catastrophe bond, namely zero coupon bonds, ‘coupon only at risk’ bond, and ‘principal and coupon at risk’ bond. Relationship between price of the catastrophe bond and CIR model’s parameter, GEV’s parameter, percentage of coupon, and discounted cash flow rule then explained via Monte Carlo simulation

  9. Valence quark polarization in the nucleon and the deuteron data

    Science.gov (United States)

    Arash, Firooz; Taghavi-Shahri, Fatemeh

    2008-10-01

    Within the framework of the so-called valon model, we argue that a substantial part of the nucleon spin, about 40%, is carried by the polarized valence quarks. The remaining is the result of cancelations between gluon polarization and the orbital angular momentum, where the gluon polarization is the dominant one. It is shown that the sea quark contributions to the spin of any hadron is simply marginal and consistent with zero. Our findings point to a substantially smaller value for a8 than inferred from hyperon β decay, suggesting that full SU (3) symmetric assumption needs to be reconsidered. New and emerging experimental data tend to support this finding. Finally, we show that within the model presented here the experimental data on the polarized structure functions g1p,n,d are reproduced.

  10. Bond diluted Levy spin-glass model and a new finite size scaling method to determine a phase transition

    CERN Document Server

    Leuzzi, L; Ricci-Tersenghi, F; Ruiz-Lorenzo, J J

    2010-01-01

    A spin-glass transition occurs both in and out of the limit of validity of mean-field theory on a diluted one dimensional chain of Ising spins where exchange bonds occur with a probability decaying as the inverse power of the distance. Varying the power in this long-range model corresponds, in a one-to-one relationship, to change the dimension in spin-glass short-range models. Using different finite size scaling methods evidence for a spin-glass transition is found also for systems whose equivalent dimension is below the upper critical dimension at zero magnetic field. The application of a new method is discussed, that can be exported to systems in a magnetic field.

  11. The solid solutions CeRu{sub 1-x}Pd{sub x}Sn and CeRh{sub 1-x}Pd{sub x}Sn. Applicability of the ICF model to determine intermediate cerium valencies by comparison with XANES data

    Energy Technology Data Exchange (ETDEWEB)

    Niehaus, Oliver; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Abdala, Paula M. [European Synchrotron Radiation Facility (ESRF), Grenoble (France). SNBL

    2015-07-01

    Several samples of the solid solutions CeRu{sub 1-x}Pd{sub x}Sn and CeRh{sub 1-x}Pd{sub x}Sn have been synthesized by arc-melting and characterized by X-ray powder diffraction. Guinier powder patterns prove that the ZrNiAl-type structure is the dominating one, besides the CeRuSn and TiNiSi type structures. The structures of CeRu{sub 0.28}Pd{sub 0.72}Sn (ZrNiAl type, P anti 62m, a = 751.95(3), c = 418.70(2) pm, wR2 = 0.0274, 332 F{sup 2} values, 14 variables) and CeRh{sub 0.66}Pd{sub 0.34}Sn (ZrNiAl type, P anti 62m, a = 750.26(3), c = 411.59(2) pm, wR2 = 0.0533, 358 F{sup 2} values, 14 variables) were refined from single crystal diffractometer data. Magnetic measurements in combination with XANES (X-Ray Absorption Near Edge Structure) clearly proved intermediate cerium valencies for most compounds and revealed the best fitting parameters for those with the ICF model (Interconfiguration fluctuation). The electrical resistivity is also influenced by the substitutions. At low and high valence electron counts (VECs) metallic character is present, while around the VEC of CeRhSn the typical resistivity behavior for valence fluctuating compounds is observed.

  12. Human Amygdala Represents the Complete Spectrum of Subjective Valence

    OpenAIRE

    Jin, Jingwen; Zelano, Christina; Gottfried, Jay A.; Mohanty, Aprajita

    2015-01-01

    Although the amygdala is a major locus for hedonic processing, how it encodes valence information is poorly understood. Given the hedonic potency of odor stimuli and the amygdala's anatomical proximity to the peripheral olfactory system, we combined high-resolution fMRI with pattern-based multivariate techniques to examine how valence information is encoded in the amygdala. Ten human subjects underwent fMRI scanning while smelling 9 odorants that systematically varied in perceived valence. Re...

  13. 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....

  14. The valence electron structure and property analysis of TiC

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The valence electron structure of TiC was calculated by using the empirical electron theory of solids and molecules. The calculated results show that with the increase of temperature the number of common electrons of TiC increases, which indicates that TiC has a good thermal sta-bility; and there exists a close relationship between hardness and brittleness of TiC. According to the number of lattice electrons, the differences among the crystals with different structures can be explained qualitatively. Using the "bond- strengthening factor", the differences of hardness among the crystals with different structures can also be qualitatively explained to some extent.

  15. 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.

  16. 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:

  17. The nature of chemical bonds from PNOF5 calculations.

    Science.gov (United States)

    Matxain, Jon M; Piris, Mario; Uranga, Jon; Lopez, Xabier; Merino, Gabriel; Ugalde, Jesus M

    2012-06-18

    Natural orbital functional theory (NOFT) is used for the first time in the analysis of different types of chemical bonds. Concretely, the Piris natural orbital functional PNOF5 is used. It provides a localization scheme that yields an orbital picture which agrees very well with the empirical valence shell electron pair repulsion theory (VSEPR) and Bent's rule, as well as with other theoretical pictures provided by valence bond (VB) or linear combination of atomic orbitals-molecular orbital (LCAO-MO) methods. In this context, PNOF5 provides a novel tool for chemical bond analysis. In this work, PNOF5 is applied to selected molecules that have ionic, polar covalent, covalent, multiple (σ and π), 3c-2e, and 3c-4e bonds. PMID:22615195

  18. DFT modeling of the electronic and magnetic structures and chemical bonding properties of intermetallic hydrides

    International Nuclear Information System (INIS)

    This thesis presents an ab initio study of several classes of intermetallics and their hydrides. These compounds are interesting from both a fundamental and an applied points of view. To achieve this aim two complementary methods, constructed within the DFT, were chosen: (i) pseudo potential based VASP for geometry optimization, structural investigations and electron localization mapping (ELF), and (ii) all-electrons ASW method for a detailed description of the electronic structure, chemical bonding properties following different schemes as well as quantities depending on core electrons such as the hyperfine field. A special interest is given with respect to the interplay between magneto-volume and chemical interactions (metal-H) effects within the following hydrided systems: binary Laves (e.g. ScFe2) and Haucke (e.g. LaNi5) phases on one hand, and ternary cerium based (e.g. CeRhSn) and uranium based (e.g. U2Ni2Sn) alloys on the other hand. (author)

  19. A Molecular Perspective of Inter-filament Bonding in Fused Deposition Modeling 3-D Printing

    Science.gov (United States)

    Duranty, Edward; Spradlin, Brandon; Dadmun, Mark

    2015-03-01

    Fused deposition 3D printing is an important tool for low-cost and rapid prototyping of objects with complex geometries. 3D printed materials are composed of many filaments deposited on a heated substrate, requiring the bonding of neighboring filaments during the deposition process. Filament deposition often creates voids between filaments, which requires necking between them to create a robust sample. Therefore the amount of interfacial contact and interdiffusion between filaments become important parameters that control the macroscopic physical properties of the printed prototype. Our research focuses on quantifying the interfacial adhesion between ABS filaments and its impact on structural properties. The time evolution of the temperature profile near the heated substrate demonstrates that the deposited filaments are repeatedly heated above the Tg of ABS allowing interpenetration of the polymer chains between adjacent filaments. Results of DMA experiments on samples of different geometries have been correlated to microphotography that monitors the degree of necking between filaments and the thermal history. Results indicate that interfacial contact area between filaments and increased thermal energy are crucial to their mechanical properties.

  20. Fundamental ultrasonic wave propagation studies in a model thermal protection system (porous tiles bonded to aluminum bulkhead)

    Science.gov (United States)

    Kundu, Tribikram; Reibel, Richard; Jata, Kumar V.

    2006-03-01

    A model thermal protection system (TPS) was designed by bonding ceramic porous tiles to 2.2 and 3.5 mm thick 2124-T351 aluminum alloy plates. One of the goals of the present work was to investigate the potential of detecting simulated defects using guided waves. Simulated defects consisted of cracks, voids and delaminations at the tile-substrate interface. Cracks and voids were introduced into the porous tiles during the fabrication of the TPS. Delamination was created by cutting the gluing tape between the tile and the aluminum substrate. Guided wave propagation studies were conducted using the pitch-catch approach, while changing the angle of strike and the frequency of the transducer excitation to generate the appropriate guided wave mode. The receiver was placed at a distance so that only the guided waves were received during the immersion experiment. The delamination defect could be conclusively detected, however the presence of the imperfect bond between the tiles and the substrate interfered with the detection of the simulated cracks and voids in the porous tiles.

  1. Use of Self-Assembling Monolayers to Control Interface Bonding in a Model Study of Interfacial Fracture

    Energy Technology Data Exchange (ETDEWEB)

    Kent, M.S.; Matheson, A.; Reedy, E.D.; Yim, H.

    1999-03-05

    The relationships between the extent of interfacial bonding, energy dissipation mechanisms, and fracture toughness in a glassy adhesive/inorganic solid joint are not well understood. We address this subject with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The extent of interfacial bonding, and the wetting behavior of the epoxy, is varied continuously using self-assembling monolayers (SAMs) of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but forms only a very weak interface with the methylated tails of the ODTS monolayer. We examine the fracture behavior of such joints as a function of the coverage of ODTS in the napkin-ring geometry. Various characterization methods are applied to the ODTS-coated surface before application of the epoxy, and to both surfaces after fracture. The fracture data are discussed with respect to the wetting of the liquid epoxy on the ODTS-coated substrates, the locus of failure, and the energy dissipation mechanisms. Our goal is to understand how energy is dissipated during fracture as a function of interface strength.

  2. 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.

  3. Use of bond-valence sums in modelling the diffuse scattering from PZN (PbZn.sub.1/3./sub.Nb.sub.2/3./sub.O.sub.3./sub.)

    Czech Academy of Sciences Publication Activity Database

    Whitfield, R.E.; Welberry, T.R.; Pasciak, Marek; Goossens, D.J.

    2014-01-01

    Roč. 70, Nov (2014), 626-635. ISSN 0108-7673 Institutional support: RVO:68378271 Keywords : relaxor ferroelectrics * local structure * diffuse scattering * Monte Carlo simulation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.307, year: 2014

  4. Theoretical study on O$\\cdots$Br and O$\\cdots$Cl halogen bonds in some small model molecular systems

    Indian Academy of Sciences (India)

    Damanjit Kaur; Rajinder Kaur

    2014-11-01

    Halogen bonding interactions of type X$\\cdots$O=C are important in various fields including biological systems. In this work, theoretical calculations were carried out using B3LYP/6-31++G∗∗, MP2/6-31++G∗∗ and MP2/aug-cc-pVDZ methods on a series of O$\\cdots$X halogen bonds between CH2O andCH3CHO as halogen bond acceptor with X-Y (X = Cl, Br; Y = CF3, CF2 H, CFH2, CN, CCH, CCCN) as halogen bond donors. The strength of interaction energy for O$\\cdots$Br halogen-bonded complexes varies from −2.16 to −5.26 kcal/mol while for O$\\cdots$Cl complexes, it is between −1.65 to −3.67 kcal/mol, which indicate the O$\\cdots$Br bond to be stronger in comparison to O$\\cdots$Cl bond. SAPT analysis suggests that the strength of halogen bonding arises from the electrostatic and induction forces while dispersion is playing a comparatively smaller role. The halogen-bonded interaction energies were found to correlate well with positive electrostatic potential VS,max, halogen bonded distances, and the change in s-character of C-X bond. The halogen-bonded interaction energies were also evaluated for O$\\cdots$I bonded complexes and thus these complexes were found to be stronger than O$\\cdots$Br and O$\\cdots$Cl bonded complexes.

  5. Modulus of unbounded valence subdivision rules

    CERN Document Server

    Rushton, Brian

    2011-01-01

    Cannon, Floyd and Parry have studied the modulus of finite subdivision rules extensively. We investigate the properties of the modulus of subdivision rules with linear and exponential growth at every vertex, using barycentric subdivision and a subdivision rule for the Borromean rings as examples. We show that the subdivision rule arising from the Borromean rings is conformal, and conjecture that the subdivision rules for all alternating links are conformal. We show that the 1,2,3-tile criterion of Cannon, Floyd, and Parry is sufficient to prove conformality for linear growth, but not exponential growth. We show that the criterion gives a weaker form of conformality for subdivision rules of exponential growth at each vertex. We contrast this with the known, bounded-valence case, and illustrate our results with circle packings using Ken Stephenson's Circlepack.

  6. Accurate valence band width of diamond

    International Nuclear Information System (INIS)

    An accurate width is determined for the valence band of diamond by imaging photoelectron momentum distributions for a variety of initial- and final-state energies. The experimental result of 23.0±0.2 eV2 agrees well with first-principles quasiparticle calculations (23.0 and 22.88 eV) and significantly exceeds the local-density-functional width, 21.5±0.2 eV2. This difference quantifies effects of creating an excited hole state (with associated many-body effects) in a band measurement vs studying ground-state properties treated by local-density-functional calculations. copyright 1997 The American Physical Society

  7. The introduction of hydrogen bond and hydrophobicity effects into the rotational isomeric states model for conformational analysis of unfolded peptides

    International Nuclear Information System (INIS)

    Relative contributions of local and non-local interactions to the unfolded conformations of peptides are examined by using the rotational isomeric states model which is a Markov model based on pairwise interactions of torsion angles. The isomeric states of a residue are well described by the Ramachandran map of backbone torsion angles. The statistical weight matrices for the states are determined by molecular dynamics simulations applied to monopeptides and dipeptides. Conformational properties of tripeptides formed from combinations of alanine, valine, tyrosine and tryptophan are investigated based on the Markov model. Comparison with molecular dynamics simulation results on these tripeptides identifies the sequence-distant long-range interactions that are missing in the Markov model. These are essentially the hydrogen bond and hydrophobic interactions that are obtained between the first and the third residue of a tripeptide. A systematic correction is proposed for incorporating these long-range interactions into the rotational isomeric states model. Preliminary results suggest that the Markov assumption can be improved significantly by renormalizing the statistical weight matrices to include the effects of the long-range correlations

  8. Under-coordinated atoms induced local strain, quantum trap depression and valence charge polarization at W stepped surfaces

    International Nuclear Information System (INIS)

    We have explored the effects of atoms under-coordination on surface structure relaxation, binding energy shift of W stepped surfaces and valence charge polarization by the method of incorporating bond order-length-strength (BOLS) correlation mechanism into high-resolution X-ray photoluminescence spectra (XPS) measurements as well as density functional theory (DFT) calculations. Results show that the 4f7/2 energy levels of bulk, surface skin and step edge W atoms shift deeper from 2.17 to 2.69 eV with respect to that of the isolated W (28.91±0.01 eV) atoms, while the valence charge energy shift upper from inner to outer layer and from bulk to stepped edge. The surface bond contraction occurs around under-coordinated atoms after geometry relaxation calculation. Consistency among BOLS calculations, DFT calculation and experimental measurements clarifies that the surface bond contraction and consolidation due to the effects of under-coordination atoms induce potential trap depression, which provides perturbation to the Hamiltonian and hence contributes to the surface core level shift deeper, and that the surface valence charge are polarized by the densely trapped core-level electrons to upper energy.

  9. Renormalization group solution for the two-dimensional random bond Potts model with broken replica symmetry

    CERN Document Server

    Dotsenko, V S; Picco, M; Pujol, P; Dotsenko, Viktor; Dotsenko, Vladimir; Picco, Marco; Pujol, Pierre

    1995-01-01

    We find a new solution of the renormalization group for the Potts model with ferromagnetic random valued coupling constants. The solution exhibits universality and broken replica symmetry. It is argued that the model reaches this universality class if the replica symmetry is broken initially. Otherwise the model stays with the replica symmetric renormalization group flow and reaches the fixed point which has been considered before.

  10. Modeling liquid-vapor equilibria with an equation of state taking into account dipolar interactions and association by hydrogen bonding

    International Nuclear Information System (INIS)

    Modelling fluid-rock interactions as well as mixing and unmixing phenomena in geological processes requires robust equations of state (EOS) which must be applicable to systems containing water, gases over a broad range of temperatures and pressures. Cubic equations of state based on the Van der Waals theory (e. g. Soave-Redlich-Kwong or Peng-Robinson) allow simple modelling from the critical parameters of the studied fluid components. However, the accuracy of such equations becomes poor when water is a major component of the fluid since neither association trough hydrogen bonding nor dipolar interactions are accounted for. The Helmholtz energy of a fluid may be written as the sum of different energetic contributions by factorization of partition function. The model developed in this thesis for the pure H2O and H2S considers three contributions. The first contribution represents the reference Van der Waals fluid which is modelled by the SRK cubic EOS. The second contribution accounts for association through hydrogen bonding and is modelled by a term derived from Cubic Plus Association (CPA) theory. The third contribution corresponds to the dipolar interactions and is modelled by the Mean Spherical Approximation (MSA) theory. The resulting CPAMSA equation has six adjustable parameters, which three represent physical terms whose values are close to their experimental counterpart. This equation results in a better reproduction of the thermodynamic properties of pure water than obtained using the classical CPA equation along the vapour-liquid equilibrium. In addition, extrapolation to higher temperatures and pressure is satisfactory. Similarly, taking into account dipolar interactions together with the SRK cubic equation of state for calculating molar volume of H2S as a function of pressure and temperature results in a significant improvement compared to the SRK equation alone. Simple mixing rules between dipolar molecules are proposed to model the H2O-H2S binary system

  11. Isotopic exchange in mixed valence compounds in the solid state

    International Nuclear Information System (INIS)

    This work aims at the determination of isotopic exchange kinetics and mechanism in two mixed valence compounds: Cs10(Sbsup(V)Cl6) (Sbsup(III)Cl6)3 and Tl3sup(I)(Tlsup(III)Cl6). The synthesis of the first compound is very difficult because in most of the cases mixtures of chloroantimoniates are obtained. Exchange in Tl4Cl6 labelled on Tlsup(III) is studied in detail by radiochemical analysis and physical techniques: ionic conductivity and positon annihilation. Cation vacancies are easily created in the lattice with formation enthalpy of 0.35 eV and migration enthalpy of 0.52 eV. Isochronic and isothermal exchange curves are described by a kinetic based on species diffusion. Models are given. Exchange is increased by grinding probably because extrinseque defects are introduced

  12. Electric-field-driven electron-transfer in mixed-valence molecules

    Science.gov (United States)

    Blair, Enrique P.; Corcelli, Steven A.; Lent, Craig S.

    2016-07-01

    Molecular quantum-dot cellular automata is a computing paradigm in which digital information is encoded by the charge configuration of a mixed-valence molecule. General-purpose computing can be achieved by arranging these compounds on a substrate and exploiting intermolecular Coulombic coupling. The operation of such a device relies on nonequilibrium electron transfer (ET), whereby the time-varying electric field of one molecule induces an ET event in a neighboring molecule. The magnitude of the electric fields can be quite large because of close spatial proximity, and the induced ET rate is a measure of the nonequilibrium response of the molecule. We calculate the electric-field-driven ET rate for a model mixed-valence compound. The mixed-valence molecule is regarded as a two-state electronic system coupled to a molecular vibrational mode, which is, in turn, coupled to a thermal environment. Both the electronic and vibrational degrees-of-freedom are treated quantum mechanically, and the dissipative vibrational-bath interaction is modeled with the Lindblad equation. This approach captures both tunneling and nonadiabatic dynamics. Relationships between microscopic molecular properties and the driven ET rate are explored for two time-dependent applied fields: an abruptly switched field and a linearly ramped field. In both cases, the driven ET rate is only weakly temperature dependent. When the model is applied using parameters appropriate to a specific mixed-valence molecule, diferrocenylacetylene, terahertz-range ET transfer rates are predicted.

  13. Universality Class of the Nishimori Point in the 2D ±J Random-Bond Ising Model

    International Nuclear Information System (INIS)

    We study the universality class of the Nishimori point in the 2D ±J random-bond Ising model by means of the numerical transfer-matrix method. Using the domain-wall free energy, we locate the position of the fixed point along the Nishimori line at the critical concentration value pc=0.1094±0.0002 and estimate ν=1.33±0.03 . Then, we obtain the exponents for the moments of the spin-spin correlation functions as well as the value for the central charge c=0.464±0.004 . The main qualitative result is the fact that percolation is now excluded as a candidate for describing the universality class of this fixed point

  14. Infrared spectra of weak hydrogen bonds and indirect damping. On the deep connection between the quantum model and the semi-classical one of Robertson and Yarwood

    International Nuclear Information System (INIS)

    The classical approximation of the quantum model dealing with the IR spectra of weak hydrogen bond involving indirect damping [B. Boulil, O. Henri-Rousseau, P. Blaise, Chem. Phys. 126 (1988) 263] is obtained. It transforms, via a crude approximation concerning the interpretation of stochastic averages, into the classical Robertson-Yarwood (RY) model [G. Robertson, J. Yarwood, Chem. Phys. 32 (1978) 267

  15. 20-sim software for hierarchical bond-graph/block-diagram models

    NARCIS (Netherlands)

    Broenink, Jan F.

    1999-01-01

    We discuss the modeling and simulation package 20-sim, a tool for modeling and simulation of dynamic behavior of engineering systems. Engineering systems as application domain means that we focus on systems that span multiple physical domains and the information domain. The 20-sim software is an int

  16. Distinguishing Bonds.

    Science.gov (United States)

    Rahm, Martin; Hoffmann, Roald

    2016-03-23

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

  17. 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 are...

  18. Mechatronics by bond graphs an object-oriented approach to modelling and simulation

    CERN Document Server

    Damić, Vjekoslav

    2015-01-01

    This book presents a computer-aided approach to the design of mechatronic systems. Its subject is an integrated modeling and simulation in a visual computer environment. Since the first edition, the simulation software changed enormously, became more user-friendly and easier to use. Therefore, a second edition became necessary taking these improvements into account. The modeling is based on system top-down and bottom-up approach. The mathematical models are generated in a form of differential-algebraic equations and solved using numerical and symbolic algebra methods. The integrated approach developed is applied to mechanical, electrical and control systems, multibody dynamics, and continuous systems. .

  19. Improve regression-based models for prediction of internal-bond strength of particleboard using Buckingham's pi-theorem

    Institute of Scientific and Technical Information of China (English)

    Akbar Rostampour Haftkhani; Mohammad Arabi

    2013-01-01

    Internal bond (IB) strength is one of the most important me-chanical properties that indicate particleboard quality. The aim of this study was to find a simple regression model that considers the most important parameters that can influence on IB strength. In this study, IB strength was predicted by three kinds of equations (linear, quadratic, and exponential) that were based on the percentage of adhesive (8%, 9.5%, and 11%), particle size (+5, -5 +8, -8 12, and -12 mesh), and density (0.65, 0.7, and 0.75 g/cm3). Our analysis of the results (using SHAZAM 9 software) showed that the exponential function best fitted the experi-mental data and predicted the IB strength with 18% error. In order de-crease the error percentage, the Buckingham Pi theorem was used to build regression models for predicting IB strength based on particle size, density, percentage of adhesive, face-screw withdrawal resistance (SWRf), and edge-screw withdrawal resistance (SWRe). From there, three dimensionless groups were created by Buckingham’s Pi theorem and IB strength was predicted based on multiple regression models. The results showed these models can predict IB strength with 10.68% and 18.17%error, based on face-screw withdrawal resistance and edge-screw withdrawal resistance, respectively.

  20. Evaluation of Bonding Orbitals in Amorphous Silicon by Means of the Chemical Pseudopotential Method

    OpenAIRE

    Grado Caffaro, M. A.; Grado Caffaro, M.

    1994-01-01

    The chemical pseudopotential method has been used by a number of workers in order to study the valence bands of amorphous tetrahedrally bonded semiconductors. However, various problems related to this method are unsolved. In this paper, a theoretical formulation tending to clarify some of these. problems is presented. This formulation concerns bonding orbitals and is valid, in principle, for amorphous silicon.

  1. Teaching Valence Shell Electron Pair Repulsion (VSEPR) Theory

    Science.gov (United States)

    Talbot, Christopher; Neo, Choo Tong

    2013-01-01

    This "Science Note" looks at the way that the shapes of simple molecules can be explained in terms of the number of electron pairs in the valence shell of the central atom. This theory is formally known as valence shell electron pair repulsion (VSEPR) theory. The article explains the preferred shape of chlorine trifluoride (ClF3),…

  2. On the Relationship between Value Orientation, Valences, and Academic Achievement

    Science.gov (United States)

    Fries, Stefan; Schmid, Sebastian; Hofer, Manfred

    2007-01-01

    Value orientations are believed to influence learning in school. We assume that this influence is mediated by the valences attached to specific school subjects. In a questionnaire study (704 students from 36 classes) achievement and well-being value orientations were measured. Students also rated valence scales for the school subjects German and…

  3. Orientational bond and N\\'eel order in the two-dimensional ionic Hubbard model

    OpenAIRE

    Hafez-Torbati, Mohsen; Uhrig, Götz S.

    2015-01-01

    Unconventional phases often occur where two competing mechanisms compensate. An excellent example is the ionic Hubbard model where the alternating local potential $\\delta$, favoring a band insulator (BI), competes with the local repulsion $U$, favoring a Mott insulator (MI). By continuous unitary transformations we derive effective models in which we study the softening of various excitons. The softening signals the instability towards new phases that we describe on the mean-field level. On i...

  4. Effect of phenyl and benzyl group in heterocyclic dithiocarbamates on the ZnS 4N chromophore: Synthesis, spectral, valence-bond parameters and single crystal X-ray structural studies on (pyridine)bis(1,2,3,4-tetrahydroquinolinedithiocarbamato)zinc(II) and (pyridine)bis(1,2,3,4-tetrahydroisoquinolinedithiocarbamato)zinc(II)

    Science.gov (United States)

    Srinivasan, N.; Thirumaran, S.; Ciattini, Samuele

    2009-03-01

    Two Zn(II)dithiocarbamates with ZnS 4N chromophores have been synthesized ([Zn(thqdtc) 2(py)] ( 1) and [Zn(thiqdtc) 2(py)] ( 2) (where thqdtc = 1,2,3,4-tetrahydroquinolinedithiocarbamate, thiqtc = 1,2,3,4-tetrahydroisoquinolinedithiocarbamate and py = pyridine)) from [Zn(thqdtc) 2] ( 3) and [Zn(thiqdtc) 2] ( 4), respectively. Their structures and properties have been characterized by IR and NMR spectra. The structures of both the complexes were determined by single crystal X-ray crystallography. The observed deshielding of the H-2 protons for 1 and 3 and H-1 and H-3 protons for 2 and 4 in the 1H NMR spectra is attributed to the drift of electrons from the nitrogen of the NR 2 group, forcing a high electron density towards sulfur via the thioureide π-system. In the 13C NMR spectra, the most important thioureide (N 13CS 2) carbon signals are observed in the region 204-207 ppm. The upfield shift of NCS 2 carbon signal for 1 (204.2 ppm) from the chemical shift value of 2 (206.9 ppm) is due to electron withdrawing resonance effect of phenyl ring thereby decreasing the double bond character in tetrahydroquinolinedithiocarbamate, whereas benzyl group in tetrahydroisoquinolinedithiocarbamate cannot participate in resonance delocalization in the same way. Single crystal X-ray structural analysis of 1 and 2 showed that the zinc atom is pentacoordinated with four sulfur atoms from the dithiocarbamate ligands and one nitrogen atom from the pyridine. VBS values support the correctness of the determined structure. The lower VBS value of 2 is due to the steric effect exerted by the thiqdtc. The phenyl and benzyl group in the heterocyclic dithiocarbamates influences the electronic properties of 1 and 2. The shift of ν C- N(thioureide) and thioureide N 13CS 2 carbon signals are correlated with the electronic effects of the dithiocarbamate ligands.

  5. Dynamic modeling and analysis of the PZT-bonded composite Timoshenko beams: Spectral element method

    Science.gov (United States)

    Lee, Usik; Kim, Daehwan; Park, Ilwook

    2013-03-01

    The health of thin laminated composite beams is often monitored using the ultrasonic guided waves excited by wafer-type piezoelectric transducers (PZTs). Thus, for the smart composite beams which consist of a laminated composite base beam and PZT layers, it is very important to develop a very reliable mathematical model and to use a very accurate computational method to predict accurate dynamic characteristics at very high ultrasonic frequency. In this paper, the axial-bending-shear-lateral contraction coupled differential equations of motion are derived first by the Hamilton's principle with Lagrange multipliers. The smart composite beam is represented by a Timoshenko beam model by adopting the first-order shear deformation theory (FSDT) for the laminated composite base beam. The axial deformation of smart composite beam is improved by taking into account the effects of lateral contraction by adopting the concept of Mindlin-Herrmann rod theory. The spectral element model is then formulated by the variation approach from coupled differential equations of motion transformed into the frequency domain via the discrete Fourier transform. The high accuracy of the present spectral element model is verified by comparing with other solution methods: the finite element model developed in this paper and the commercial FEA package ANSYS. Finally the dynamics and wave characteristics of some example smart composite beams are investigated through the numerical studies.

  6. Chemical Bond Parameters in Sr3MRhO6 (M=Rare earth)

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Chemical bond parameters, that is, bond covalency, bond valence, macroscopic linear susceptibility, and oxidation states of elements in Sr3MRhO6 (M=Sm, Eu, Tb, Dy, Ho, Er, Yb) have been calculated. The results indicate that the bond covalency of M-O decreases sharply with the decrease of ionic radius of M3+ from Sm to Yb, while no obvious trend has been found for Rh-O and Sr-O bonds. The global instability index indicates that the crystal structures of Sr3MrhO6 (M = Sm, Eu, Tb, Dy, Ho) have strained bonds.

  7. A density functional for core-valence correlation energy

    Science.gov (United States)

    Ranasinghe, Duminda S.; Frisch, Michael J.; Petersson, George A.

    2015-12-01

    A density functional, ɛCV-DFT(ρc, ρv), describing the core-valence correlation energy has been constructed as a linear combination of ɛLY Pcorr(ρc), ɛV WN5corr(ρc, ρv), ɛPBEcorr(ρc, ρv), ɛSlaterex(ρc, ρv), ɛHCTHex(ρc, ρv), ɛHFex(ρc, ρv), and F CV -DFT (" separators=" N i , Z i ) , a function of the nuclear charges. This functional, with 6 adjustable parameters, reproduces (±0.27 kcal/mol rms error) a benchmark set of 194 chemical energy changes including 9 electron affinities, 18 ionization potentials, and 167 total atomization energies covering the first- and second-rows of the periodic table. This is almost twice the rms error (±0.16 kcal/mol) obtained with CCSD(T)/MTsmall calculations, but less than half the rms error (±0.65 kcal/mol) obtained with MP2/GTlargeXP calculations, and somewhat smaller than the rms error (±0.39 kcal/mol) obtained with CCSD/MTsmall calculations. The largest positive and negative errors from ɛCV-DFT(ρc, ρv) were 0.88 and -0.75 kcal/mol with the set of 194 core-valence energy changes ranging from +3.76 kcal/mol for the total atomization energy of propyne to -9.05 kcal/mol for the double ionization of Mg. Evaluation of the ɛCV-DFT(ρc, ρv) functional requires less time than a single SCF iteration, and the accuracy is adequate for any model chemistry based on the CCSD(T) level of theory.

  8. A density functional for core-valence correlation energy.

    Science.gov (United States)

    Ranasinghe, Duminda S; Frisch, Michael J; Petersson, George A

    2015-12-01

    A density functional, εCV-DFT(ρc, ρv), describing the core-valence correlation energy has been constructed as a linear combination of εLY P (corr)(ρc), εV WN5 (corr)(ρc, ρv), εPBE (corr)(ρc, ρv), εSlater (ex)(ρc, ρv), εHCTH (ex)(ρc, ρv), εHF (ex)(ρc, ρv), and FCV-DFTNi,Zi, a function of the nuclear charges. This functional, with 6 adjustable parameters, reproduces (±0.27 kcal/mol rms error) a benchmark set of 194 chemical energy changes including 9 electron affinities, 18 ionization potentials, and 167 total atomization energies covering the first- and second-rows of the periodic table. This is almost twice the rms error (±0.16 kcal/mol) obtained with CCSD(T)/MTsmall calculations, but less than half the rms error (±0.65 kcal/mol) obtained with MP2/GTlargeXP calculations, and somewhat smaller than the rms error (±0.39 kcal/mol) obtained with CCSD/MTsmall calculations. The largest positive and negative errors from εCV-DFT(ρc, ρv) were 0.88 and -0.75 kcal/mol with the set of 194 core-valence energy changes ranging from +3.76 kcal/mol for the total atomization energy of propyne to -9.05 kcal/mol for the double ionization of Mg. Evaluation of the εCV-DFT(ρc, ρv) functional requires less time than a single SCF iteration, and the accuracy is adequate for any model chemistry based on the CCSD(T) level of theory. PMID:26646873

  9. Fault diagnosis of locomotive electro-pneumatic brake through uncertain bond graph modeling and robust online monitoring

    Science.gov (United States)

    Niu, Gang; Zhao, Yajun; Defoort, Michael; Pecht, Michael

    2015-01-01

    To improve reliability, safety and efficiency, advanced methods of fault detection and diagnosis become increasingly important for many technical fields, especially for safety related complex systems like aircraft, trains, automobiles, power plants and chemical plants. This paper presents a robust fault detection and diagnostic scheme for a multi-energy domain system that integrates a model-based strategy for system fault modeling and a data-driven approach for online anomaly monitoring. The developed scheme uses LFT (linear fractional transformations)-based bond graph for physical parameter uncertainty modeling and fault simulation, and employs AAKR (auto-associative kernel regression)-based empirical estimation followed by SPRT (sequential probability ratio test)-based threshold monitoring to improve the accuracy of fault detection. Moreover, pre- and post-denoising processes are applied to eliminate the cumulative influence of parameter uncertainty and measurement uncertainty. The scheme is demonstrated on the main unit of a locomotive electro-pneumatic brake in a simulated experiment. The results show robust fault detection and diagnostic performance.

  10. Adsorption of indole and quinoline from a model fuel on functionalized MIL-101: effects of H-bonding and coordination.

    Science.gov (United States)

    Seo, Pill Won; Ahmed, Imteaz; Jhung, Sung Hwa

    2016-06-01

    Denitrogenation of a model fuel was studied by employing the adsorption of indole (IND) and quinoline (QUI) over a metal-organic framework (MOF), MIL-101, with or without functionalization. Five MIL-101 MOFs were obtained by direct syntheses, grafting, and hydrogenation. The adsorption capacity of IND increased significantly (up to 1.7 times that of MIL-101) upon introducing amino functional groups into MIL-101, despite the decrease in the porosity of the MOF after modification. However, the adsorption of QUI decreased when MIL-101 was modified using both amino and butyl groups because of the reduced porosity. The adsorption capacity for IND (based on the unit surface area of MIL-101s) showed that MIL-101s with amino groups had an adsorption capacity of around 2.3 times those of MIL-101 or MIL-101 with butyl groups, showing the importance of H-bonds for the adsorption of IND over MIL-101s. However, for the adsorption of QUI, only the porosity is important, and coordination of QUI on open metal sites does not play a dominant role, probably because of the low basicity of QUI. Moreover, there is little contribution of H-bonds (between N of QUI and H of -NH2 of MOF) in the adsorption of QUI over amino-MIL-101s, and this is probably due to a similar reason. Preparation methods for MIL-101 having a free amino group did not have any effect on the adsorption (based on surface area) of QUI or IND. PMID:27117231

  11. A New Lease of Life for Thomson's Bonds Model of Intelligence

    Science.gov (United States)

    Bartholomew, David J.; Deary, Ian J.; Lawn, Martin

    2009-01-01

    Modern factor analysis is the outgrowth of Spearman's original "2-factor" model of intelligence, according to which a mental test score is regarded as the sum of a general factor and a specific factor. As early as 1914, Godfrey Thomson realized that the data did not require this interpretation and he demonstrated this by proposing what became…

  12. A simple and realistic model system for studying hydrogen bonds in beta-sheets

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Hinnemann, Berit; Jacobsen, Karsten Wedel;

    2003-01-01

    We investigate the interaction between peptide chains at the level of state-of-the-art ab initio density functional theory. We propose an interacting periodic polypeptide model for studying the interactions in beta-sheets and apply this to glycine and alanine peptide chains in both parallel and...

  13. Analytical model of asymmetrical Mixed-Mode Bending test of adhesively bonded GFRP joint

    Czech Academy of Sciences Publication Activity Database

    Ševčík, Martin; Hutař, Pavel; Vassilopoulos, Anastasios P.; Shahverdi, M.

    2015-01-01

    Roč. 9, č. 34 (2015), s. 237-246. ISSN 1971-8993 R&D Projects: GA MŠk(CZ) EE2.3.30.0063; GA ČR GA15-09347S Institutional support: RVO:68081723 Keywords : GFRP materials * Mixed-Mode bending * Fiber bridging * Analytical model Subject RIV: JL - Materials Fatigue, Friction Mechanics

  14. Atom-specific look at the surface chemical bond using x-ray emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nilsson, A.; Wassdahl, N.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    CO and N{sub 2} adsorbed on the late transition metals have become prototype systems regarding the general understanding of molecular adsorption. It is in general assumed that the bonding of molecules to transition metals can be explained in terms of the interaction of the frontier HOMO and LUMO molecular orbitals with the d-orbitals. In such a picture the other molecular orbitals should remain essentially the same as in the free molecule. For the adsorption of the isoelectronic molecules CO and N{sub 2} this has led to the so called Blyholder model i.e., a synergetic {sigma} (HOMO) donor and {pi} (LUMO) backdonation bond. The authors results at the ALS show that such a picture is oversimplified. The direct observation and identification of the states related to the surface chemical bond is an experimental challenge. For noble and transition metal surfaces, the adsorption induced states overlap with the metal d valence band. Their signature is therefore often obscured by bulk substrate states. This complication has made it difficult for techniques such as photoemission and inverse photoemission to provide reliable information on the energy of chemisorption induced states and has left questions unanswered regarding the validity of the frontier orbitals concept. Here the authors show how x-ray emission spectroscopy (XES), in spite of its inherent bulk sensitivity, can be used to investigate adsorbed molecules. Due to the localization of the core-excited intermediate state, XE spectroscopy allows an atomic specific separation of the valence electronic states. Thus the molecular contributions to the surface measurements make it possible to determine the symmetry of the molecular states, i.e., the separation of {pi} and {sigma} type states. In all the authors can obtain an atomic view of the electronic states involved in the formation of the chemical bond to the surface.

  15. Phenomenological many‐body potentials from the interstitial electron model. I. Dynamic properties of metals

    OpenAIRE

    Li, Mo; Goddard, William A.

    1993-01-01

    Inspired by the ab initio generalized‐valence‐bond calculations of small metal clusters, we propose a phenomenological many‐body interaction model, the interstitial electron model (IEM), for interactions of ions and electrons in metals. In this model, the valence electrons are treated as classical particles situated at the crystal lattice interstitial positions. Simple pair potentials are used for ions and interstitial electrons, allowing the inhomogeneity and anisotropy of electron density d...

  16. On possible reasons of Mo-Sn σ-bond shortening in heterometallic complexes of (η5-C5H5)2Mo(H)Sn(CH3)nCl3-n composition

    International Nuclear Information System (INIS)

    As possible reasons of Mo-Sn σ-bond shortening in heterometallic complexes of (η5-C5H5)2Mo(H)Sn(CH3)n composition, dative π-interaction of d-electron unshared pairs of a transition metal with vacant d-orbitals of tin atoms and redistribution of electron densities at Mo and Sn atoms, leading to a high S-character of this bond, are discussed. The most important structure characteristics of Cp2Mo(H)Sn(CH3)2Cl and Cp2Mo(H)Sn(CH3)3 complexes (interatomic distances, valence angles) and a structure model are presented. The conclusion is made that structure peculiarities and spectral properties of this complexes are explained by higher than usual S-character of Mo-Sn bond, that doesn't exclude certain participation of π-dative interaction in formation of metal-metal bond

  17. Enzymatic transformation and bonding of sulfonamide antibiotics to model humic substances

    OpenAIRE

    2015-01-01

    © 2015 J. Schwarz et al. Sulfonamides are consumed as pharmaceutical antibiotics and reach agricultural soils with excreta used as fertilizer. Subsequently, nonextractable residues rapidly form in soil, which has been researched in a couple of studies. To further elucidate conditions, strength, and mechanisms of the fixation to soil humic substances, three selected sulfonamides were investigated using the biochemical oligomerization of substituted phenols as a model for the humification proce...

  18. The Random-Bond Ising Model in 2.01 and 3 Dimensions

    CERN Document Server

    Komargodski, Zohar

    2016-01-01

    We consider the Ising model between 2 and 4 dimensions perturbed by quenched disorder in the strength of the interaction between nearby spins. In the interval 2model. We compare these new methods with previous studies. Finally, we comment about the $O(2)$ model in d=3, where we predict a large logarithmic correction to the infrared scaling of disorder.

  19. Finite Element Modelling for Tensile Behaviour of Thermally Bonded Nonwoven Fabric

    Directory of Open Access Journals (Sweden)

    Gao Xiaoping

    2015-03-01

    Full Text Available A nonwoven fabric has been widely used in geotextile engineering in recent years; its tensile strength is an important behaviour. Since the fibre distributions in nonwoven fabrics are random and discontinuous, the unit-cell model of a nonwoven fabric cannot be developed to simulate its tensile behaviour. This article presents our research on using finite element method (FEM to study the tensile behaviour of a nonwoven fabric in macro-scale based on the classical laminate composite theory. The laminate orientation was considered with orientation distribution function of fibres, which has been obtained by analysing the data acquired from scanning electron microscopy with Hough Transform. The FE model of a nonwoven fabric was developed using ABAQUS software; the required engineering constants of a nonwoven fabric were obtained from experimental data. Finally, the nonwoven specimens were stretched along with machine direction and cross direction. The experimental stress-strain curves were compared with the results of FE simulations. The approximate agreement proves the validity of an FE model, which could be used to precisely simulate the stress relaxation, strain creep, bending and shear property of a nonwoven fabric.

  20. 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

    [4]- and [6]-coordination, Na(+) in [4]- and [6]-coordination. For alkali-metal and alkaline-earth-metal ions, there is a positive correlation between cation coordination number and the grand mean incident bond-valence sum at the central cation, the values varying from 0.84 v.u. for ([5])K(+) to 1.06 v.u. for ([8])Li(+), and from 1.76 v.u. for ([7])Ba(2+) to 2.10 v.u. for ([12])Sr(2+). Bond-valence arguments suggest coordination numbers higher than [12] for K(+), Rb(+), Cs(+) and Ba(2+). PMID:27484381

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

    Science.gov (United States)

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

    2016-05-01

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

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

    Science.gov (United States)

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

    2016-05-01

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

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

    Science.gov (United States)

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

    2016-05-01

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

  4. Positron annihilation with core and valence electrons

    CERN Document Server

    Green, D G

    2015-01-01

    $\\gamma$-ray spectra for positron annihilation with the core and valence electrons of the noble gas atoms Ar, Kr and Xe is calculated within the framework of diagrammatic many-body theory. The effect of positron-atom and short-range positron-electron correlations on the annihilation process is examined in detail. Short-range correlations, which are described through non-local corrections to the vertex of the annihilation amplitude, are found to significantly enhance the spectra for annihilation on the core orbitals. For Ar, Kr and Xe, the core contributions to the annihilation rate are found to be 0.55\\%, 1.5\\% and 2.2\\% respectively, their small values reflecting the difficulty for the positron to probe distances close to the nucleus. Importantly however, the core subshells have a broad momentum distribution and markedly contribute to the annihilation spectra at Doppler energy shifts $\\gtrsim3$\\,keV, and even dominate the spectra of Kr and Xe at shifts $\\gtrsim5$\\,keV. Their inclusion brings the theoretical ...

  5. Models of chemical bonding : Representations Used in School Textbooks and by Teachers and their Relation to Students´Difficulties in Understanding.

    OpenAIRE

    Bergqvist, Anna

    2012-01-01

    This thesis focuses on how school textbooks and teachers present models of chemical bonding in upper secondary schools in Sweden. In science, as well as in science education, models play a central role, but research has shown that they often are difficult for students to understand. In science education, models are presented to students mainly through textbooks and teachers, and textbooks influence teachers’ teaching. The aim of this thesis was to investigate how textbooks and teachers presen...

  6. Plant G-proteins come of age: Breaking the bond with animal models

    Science.gov (United States)

    Botella, Jimmy; Trusov, Yuri

    2016-05-01

    G-proteins are universal signal transducers mediating many cellular responses. Plant G-protein signaling has been modeled on the well-established animal paradigm but accumulated experimental evidence indicates that G-protein-dependent signaling in plants has taken a very different evolutionary path. Here we review the differences between plant and animal G-proteins reported over past two decades. Most importantly, while in animal systems the G-protein signaling cycle is activated by seven transmembrane-spanning G-protein coupled receptors, the existence of these type of receptors in plants is highly controversial. Instead plant G-proteins have been proven to be functionally associated with atypical receptors such as the Arabidopsis RGS1 and a number of receptor-like kinases. We propose that, instead of the GTP/GDP cycle used in animals, plant G-proteins are activated/de-activated by phosphorylation/de-phosphorylation. We discuss the need of a fresh new look at these signaling molecules and provide a hypothetical model that departs fromthe accepted animal paradigm.

  7. Finite element modelling of non-bonded piezo sensors for biomedical health monitoring of bones based on EMI technique

    Science.gov (United States)

    Srivastava, Shashank; Bhalla, Suresh; Madan, Alok; Gupta, Ashok

    2016-04-01

    Extensive research is currently underway across the world for employing piezo sensors for biomedical health monitoring in view of their obvious advantages such as low cost,fast dynamics response and bio-compatibility.However,one of the limitations of the piezo sensor in bonded mode based on the electro-mechanical impedance (EMI) technique is that it can cause harmful effects to the humans in terms of irritation ,bone and skin disease. This paper which is in continuation of the recent demonstration of non-bonded configuration is a step towards simulating and analyzing the non-bonded configuration of the piezo sensor for gauging its effectiveness using FEA software. It has been noted that the conductance signatures obtained in non-bonded mode are significantly close to the conventional bonded configuration, thus giving a positive indication of its field use.

  8. Cluster-shell competition in systems with a few alpha particles and valence neutrons

    International Nuclear Information System (INIS)

    We construct nuclear wave functions from alpha clusters and some additional valence nucleons, and allow the inter-cluster distance to change and one alpha to dissolve from the (0s)4 structure as a result of the nuclear interaction. The change of the inter-cluster distance and the dissolution of the alpha particle can be interpreted as resulting from the competition of the 'shell model' and 'cluster model'. We demonstrate this competition through a few parameters.

  9. Modified Valence Force Field Approach for Phonon Dispersion: from Zinc-Blende Bulk to Nanowires

    OpenAIRE

    Paul, Abhijeet; Luisier, Mathieu; Klimeck, Gerhard

    2010-01-01

    The correct estimation of the thermal properties of ultra-scaled CMOS and thermoelectric semiconductor devices demands for accurate phonon modeling in such structures. This work provides a detailed description of the modified valence force field (MVFF) method to obtain the phonon dispersion in zinc-blende semiconductors. The model is extended from bulk to nanowires after incorpo- rating proper boundary conditions. The computational de- mands by the phonon calculation increase rapidly as the w...

  10. Valence selectivity of the gramicidin channel: a molecular dynamics free energy perturbation study.

    OpenAIRE

    Roux, B

    1996-01-01

    The valence selectivity of the gramicidin channel is examined using computer simulations based on atomic models. The channel interior is modeled using a gramicidin-like periodic poly (L,D)-alanine beta-helix. Free energy perturbation calculations are performed to obtain the relative affinity of K+ and Cl- for the channel. It is observed that the interior of the gramicidin channel provides an energetically favorable interaction site for a cation but not for an anion. Relative to solvation in b...

  11. An Iterated GMM Procedure for Estimating the Campbell-Cochrane Habit Formation Model, with an Application to Danish Stock and Bond Returns

    DEFF Research Database (Denmark)

    Engsted, Tom; Møller, Stig Vinther

    2010-01-01

    We suggest an iterated GMM approach to estimate and test the consumption based habit persistence model of Campbell and Cochrane, and we apply the approach on annual and quarterly Danish stock and bond returns. For comparative purposes we also estimate and test the standard constant relative risk...

  12. Diffusion bonding

    Science.gov (United States)

    Anderson, Robert C.

    1976-06-22

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

  13. Valence, magnetism and conduction in the intermediate valence compounds: the case SmB6

    International Nuclear Information System (INIS)

    In some rare earth based compounds, the 4f level is situated so close to the Fermi level that the valence of the compound can become intermediate between two integer values. The so called 'intermediate valence' compound of Samarium hexaboride (SmB6) is one typical example of the exciting physics which can result from this quantum equilibrium between two valence configurations. The first configuration (Sm2+) corresponds to an insulating and non magnetic state whereas the second one (Sm3+) would theoretically give a magnetic and metallic ground state. This dissertation deals with the influence of pressure on this equilibrium. Specific heat measurements under pressure evidenced a new long range magnetic ordering for pressures higher than pc ∼ 10 GPa. On another hand, transport measurements measured for the first time in good conditions of hydrostatics found a reliable and reproducible critical pressure for the insulator to metal transition equal to pc. The phase diagram of SmB6 is now well known and the observation for the first time of a magnetic anomaly in the high pressure resistivity curves certifies that the onset of the magnetic phase really coincide with the closure of the gap. This change at the critical pressure pc is discussed in a general frame taking into account the Kondo lattice temperature as a key parameter for the renormalization of the wavefunction from one integer configuration to the other whereas the valence itself is still intermediate. This general idea seems to be valid also for other systems studied in this dissertation like SmS or TmSe and could even be valid for more general cases (Ytterbium, Cerium). In the same time, resistivity measurements under uniaxial stress were undertaken. The result is a strong anisotropy effect observed on the pressure dependence of the residual resistivity in the compound SmB6. The comparison with the transport under hydrostatic conditions enables us to consider a new idea for the nature of the gap, considering

  14. Sulfur K-edge XAS and DFT Calculations on P450 Model Complexes: Effects of Hydrogen Bonding on Electronic Structure and Redox Potentials

    OpenAIRE

    Dey, Abhishek; Okamura, Taka-aki; Ueyama, Norikazu; Hedman, Britt; Hodgson, Keith O.; Solomon, Edward I.

    2005-01-01

    Hydrogen bonding is generally thought to play an important role in tuning the electronic structure and reactivity of metal-sulfur sites in proteins. To develop a quantitative understanding of this effect, S K-edge X-ray absorption spectroscopy (XAS) has been employed to directly probe ligand-metal bond covalency, where it has been found that protein active sites are significantly less covalent than their related model complexes. Sulfur K-edge XAS data are reported here on a series of P450 mod...

  15. Ignition experiments and models of a plastic bonded explosive (PBX 9502)

    Science.gov (United States)

    Hobbs, M. L.; Kaneshige, M. J.

    2014-03-01

    Ignition experiments from various sources, including our own laboratory, have been used to develop a simple four-step, pressure-dependent ignition model for PBX 9502, which is composed of 95% by mass triaminotrinitrobenzene (TATB) and a 5% by mass chlorotrifluoroethylene/vinylidine fluoride binder. The four-steps include drying, mono-furazan formation, and decomposition of mono-furazan and TATB into equilibrium products. Our experiments were both sealed and vented and included various ullage percentages ranging from 18% to 75% of unfilled confinement volume. Our sample densities ranged from 38% of the theoretical maximum density (TMD) to 98% TMD. We observed a decrease in ignition times with the higher density samples, an increase in ignition times with increased venting, and an increase in ignition times with increased ullage. From our experiments, we conclude that decomposition of PBX 9502 is pressure dependent, open pore decomposition occurs in low-density experiments, and that closed pore decomposition occurs when the samples are pressed to near full density. In some of our confined high-density experiments we have observed for the first time, multiple temperature excursions prior to ignition caused by internal pressure generation.

  16. Freezing transition of the random bond RNA model: Statistical properties of the pairing weights.

    Science.gov (United States)

    Monthus, Cécile; Garel, Thomas

    2007-03-01

    To characterize the pairing specificity of RNA secondary structures as a function of temperature, we analyze the statistics of the pairing weights as follows: for each base (i) of the sequence of length N , we consider the (N-1) pairing weights w{i}(j) with the other bases (j not equal i) of the sequence. We numerically compute the probability distributions P1(w) of the maximal weight w[{i}{max}=max{j}[w{i}(j)] , the probability distribution Pi(Y(2)) of the parameter Y2(i)= summation operator{j}w{i}{2}(j) , as well as the average values of the moments Y{k}(i)= summation operator_{j}w_{i}{k}(j) . We find that there are two important temperatures T_{c}T_{gap} , the distribution P1(w) vanishes at some value w{0}(T)power-law decay of the moments Y{k}(i) approximately 1k{mu(T)} . The exponent mu(T) grows from the value mu(T=0)=0 up to mu(T{gap}) approximately 2 . The study of spatial properties indicates that the critical temperature T{c} where the large-scale roughness exponent changes from the low temperature value zeta approximately 0.67 to the high temperature value zeta approximately 0.5 corresponds to the exponent mu(T{c})=1 . For Tmodel are discussed. PMID:17500664

  17. Two-dimensional, high valence-doped ceria: Ce6WO12(100)/W(110)

    Science.gov (United States)

    Stetsovych, Vitalii; Skála, Tomáš; Beran, Jan; Dvořák, Filip; Mazur, Daniel; Tsud, Nataliya; Mašek, Karel; Mysliveček, Josef; Matolín, Vladimír

    2016-05-01

    Doping of oxides for catalytic applications represents one of the most used strategies for improving their catalytic performance. Model catalyst systems for doped oxides that would contain the dopant atoms in a well-defined geometry allowing for investigation of relationships between structure and reactivity are however rare. Here we report on preparation and structural properties of two-dimensional W-doped ceria on W(110) substrate. This model system adopts geometry of two-dimensional Ce6WO12 (100)-oriented thin film, including isolated W6+ ions that donate the charge to Ce3+ ions and act as high-valence dopants. The system represents a model catalyst for prospective use in investigating the role of W6+ active sites in CeOx-WOx catalysts and high valence dopants in ceria in general.

  18. Analysis of the valence electronic structures and calculation of the physical properties of Fe, Co, and Ni

    Institute of Scientific and Technical Information of China (English)

    WU WenXia; XUE ZhiYong; HONG Xing; LI XiuMei; GUO YongQuan

    2009-01-01

    The valence electronic structures of Fe, Co and Ni have been investigated with Empirical Electron Theory of Solids and Molecules. The magnetic moments, Curie temperature, cohesive energy and melting point have been calculated according to the valence electronic structure. These calculations fit the experimental data very well. Based on the calculations, the magnetic moments are proportional to the number of 3d magnetic electrons. Curie temperatures are related to the magnetic electrons and the bond lengths between magnetic atoms. Cohesive energies increase with the increase of the number of covalent electrons, and the decrease of the number of magnetic and dumb pair electrons. The melting point is mainly related to the number of covalent electron pairs distributed in the strongest bond. The contribution from the lattice electrons is very small, the dumb pair electrons weaken the melting point; however, the contribution to melting point of the magnetic electrons can be neglected. It reveals that the magnetic and thermal properties are closely related to the valence electronic structures, and the changes or transitions between the electrons obviously affect the physical properties.

  19. Analysis of the valence electronic structures and calculation of the physical properties of Fe,Co,and Ni

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The valence electronic structures of Fe, Co and Ni have been investigated with Empirical Electron Theory of Solids and Molecules. The magnetic moments, Curie temperature, cohesive energy and melting point have been calculated according to the valence electronic structure. These calculations fit the experimental data very well. Based on the calculations, the magnetic moments are proportional to the number of 3d magnetic electrons. Curie temperatures are related to the magnetic electrons and the bond lengths between magnetic atoms. Cohesive energies increase with the increase of the number of covalent electrons, and the decrease of the number of magnetic and dumb pair electrons. The melting point is mainly related to the number of covalent electron pairs distributed in the strongest bond. The contribution from the lattice electrons is very small, the dumb pair electrons weaken the melting point; however, the contribution to melting point of the magnetic electrons can be neglected. It reveals that the magnetic and thermal properties are closely related to the valence electronic structures, and the changes or transitions between the electrons obviously affect the physical properties.

  20. Coarse grained models, bond orientational order, and the structural characterization of residue networks

    Science.gov (United States)

    Ortiz, Carlos Pompeyo

    Rigidity emerges in a broad class of soft matter systems, relevant to many industrial and biological processes. In our experiments, we study a model soft matter system, hard-sphere Brownian suspensions of submicron particles. Brownian suspensions lack rigidity in the absence of external driving, but form flow-stabilized solid-like microsphere heaps under the influence of hydrodynamic forces. The overarching question driving my dissertation is "What is the nature of the rigidity of these microsphere heaps?" Does the rigidity of the heaps follow from mechanical stability driven by a sufficiently interconnected network of particle contacts? Or, does the rigidity of the heaps follow from a kinetic glass transition characterized by a diverging resistance to flow such that the time necessary to observe rearrangements grows prohibitively large? We expect that insights into the mechanism of rigidity of Brownian microsphere heaps are applicable to a wide class of soft matter systems. In this thesis,we have overcome the limitations of previous experimental approaches. Namely, we show that the rigidity of our heaps does not emerge from the effects of gravity, inertia, static friction, or van der Waals sticking. In Chapter 1 of thesis, we review the background literature. In Chapter 2, we present the experimental, analytical, and computational methods used in the remainder of the thesis. In Chapter 3, we investigate the onset of rigidity by characterizing the steady-state size of the heap versus the imposed flow conditions. We show that thermal fluctuations and repulsive interparticle interactions, the dominant forces at the single-particle scale, suppress the development of a rigid phase. These conditions imply that the onset of rigidity in involves many-body collective interactions. In Chapter 4, we measure the response of the heap to external perturbations, which allows us to measure their elastic modulus and compare our results to hard sphere theoretical expectations. We

  1. Dynamic force spectroscopy of parallel individual mucin1-antibody bonds

    Energy Technology Data Exchange (ETDEWEB)

    Sulchek, T A; Friddle, R W; Langry, K; Lau, E; Albrecht, H; Ratto, T; DeNardo, S; Colvin, M E; Noy, A

    2005-05-02

    We used atomic force microscopy (AFM) to measure the binding forces between Mucin1 (MUC1) peptide and a single chain antibody fragment (scFv) selected from a scFv library screened against MUC1. This binding interaction is central to the design of the molecules for targeted delivery of radioimmunotherapeutic agents for prostate and breast cancer treatment. Our experiments separated the specific binding interaction from non-specific interactions by tethering the antibody and MUC1 molecules to the AFM tip and sample surface with flexible polymer spacers. Rupture force magnitude and elastic characteristics of the spacers allowed identification of the bond rupture events corresponding to different number of interacting proteins. We used dynamic force spectroscopy to estimate the intermolecular potential widths and equivalent thermodynamic off rates for mono-, bi-, and tri-valent interactions. Measured interaction potential parameters agree with the results of molecular docking simulation. Our results demonstrate that an increase of the interaction valency leads to a precipitous decline in the dissociation rate. Binding forces measured for mono and multivalent interactions match the predictions of a Markovian model for the strength of multiple uncorrelated bonds in parallel configuration. Our approach is promising for comparison of the specific effects of molecular modifications as well as for determination of the best configuration of antibody-based multivalent targeting agents.

  2. Pi Bond Orders and Bond Lengths

    Science.gov (United States)

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

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

  3. Valence and non-valence quark distribution function of hadrons in the val on model

    International Nuclear Information System (INIS)

    We calculate the par tonic structure of constitute quark in the next-to-leading order. The structure of any hadron can be obtained thereafter using a convolution method. Such a procedure is used to generate the structure function of proton and pion in Next- to- leading order

  4. Mn 3s exchange splitting in mixed-valence manganites.

    Energy Technology Data Exchange (ETDEWEB)

    Galakhov, V. R.; Demeter, M.; Bartkowski, S.; Neumann, M.; Ovechkina, N. A.; Kurmaev, E. Z.; Lobachevskaya, N. I.; Mukovskii, Ya. M.; Mitchell, J.; Ederer, D. L.; Russian Academy of Sciences; Univ. of Osnabruck; Moscow State Steel and Alloys Inst.; Tulane Univ.

    2002-03-15

    We present Mn 3s x-ray photoelectron spectra of manganese oxides with the Mn formal valency from 2+ to 4+. We found that the Sr{sup 2+} doping or cation deficiency in manganites do not change the Mn 3s splitting in manganites with the Mn formal valency from 3.0+ to 3.3+. We suggest that doping holes are localized in O 2p states.

  5. Complex verbs, simple alternations: valency and verb classes in Jaminjung.

    OpenAIRE

    Schultze-Berndt, Eva

    2012-01-01

    This chapter investigates valency patterns in Jaminjung, a language of the small Jaminjungan (or Western Mirndi) subgroup of the geographically discontinuous Mirndi language family of Northern Australia. Jaminjung is a typical “Non-Pama-Nyungan” language in that grammatical roles are indicated both by case markers and by pronominal indices (for subject and object) on inflecting verbs. Its most interesting property from the point of view of investigating valency, however, is the prevalence of ...

  6. 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.

  7. Testing Sukuk And Conventional Bond Offers Based On Corporate Financing Theories Using Partial Adjustment Models: Evidence From Malaysian Listed Firms

    OpenAIRE

    Hanifa, Mohamed Hisham; Masih, Mansur; Bacha, Obiyathulla

    2014-01-01

    Sukuk (Islamic debt securities) are dominating the Malaysian capital market with strong support from the government, mega-conglomerates and firms. Sukuk, as an important source of firms’ financing, is increasingly catching up with conventional bonds in terms of volume of transactions and number of sukuk issuances. However, from theoretical perspectives, it is still largely unknown why some firms may consider sukuk issuance while others consistently rely on conventional bond offers. In examini...

  8. Valence, arousal and cognitive control: A voluntary task switching study

    Directory of Open Access Journals (Sweden)

    JelleDemanet

    2011-11-01

    Full Text Available The present study focused on the interplay between arousal, valence and cognitive control. To this end, we investigated how arousal and valence associated with affective stimuli influenced cognitive flexibility when switching between tasks voluntarily. Three hypotheses were tested. First, a valence hypothesis that states that the positive valence of affective stimuli will facilitate both global and task-switching performance because of increased cognitive flexibility. Second, an arousal hypothesis that states that arousal, and not valence, will specifically impair task-switching performance by strengthening the previously executed task-set. Third, an attention hypothesis that states that both cognitive and emotional control ask for limited attentional resources, and predicts that arousal will impair both global and task-switching performance. The results showed that arousal affected task-switching but not global performance, possibly by phasic modulations of the noradrenergic system that reinforces the previously executed task. In addition, positive valence only affected global performance but not task-switching performance, possibly by phasic modulations of dopamine that stimulates the general ability to perform in a multitasking environment.

  9. Valence Topological Charge-Transfer Indices for Dipole Moments

    Directory of Open Access Journals (Sweden)

    Francisco Torrens

    2003-01-01

    Full Text Available New valence topological charge-transfer indices are applied to the calculation of dipole moments. The algebraic and vector semisum charge-transfer indices are defined. The combination of the charge-transfer indices allows the estimation of the dipole moments. The model is generalized for molecules with heteroatoms. The ability of the indices for the description of the molecular charge distribution is established by comparing them with the dipole moments of a homologous series of phenyl alcohols. Linear and non-linear correlation models are obtained. The new charge-transfer indices improve the multivariable non-linear regression equations for the dipole moment. When comparing with previous results, the variance decreases 92%. No superposition of the corresponding Gk–Jk and GkV – JkV pairs is observed. This diminishes the risk of co-linearity. Inclusion of the oxygen atom in the p-electron system is beneficial for the description of the dipole moment, owing to either the role of the additional p orbitals provided by the heteroatom or the role of steric factors in the p-electron conjugation. Linear and non-linear correlations between the fractal dimension and various descriptors point not only to a homogeneous molecular structure but also to the ability to predict and tailor drug properties.

  10. Bondings for tubular solar collectors

    International Nuclear Information System (INIS)

    We studied the following four models of constructing solar collectors: tubes bonded above the absorber plate, tubes bonded under the absorber plate tubes in-line with the absorber plate and bondless tubes in-line with the absorber plate. 2 refs, 6 figs

  11. Localization of the valence electron of endohedrally confined hydrogen, lithium and sodium in fullerene cages

    CERN Document Server

    Cuestas, Eloisa

    2016-01-01

    The localization of the valence electron of $H$, $Li$ and $Na$ atoms enclosed by three different fullerene molecules is studied. The structure of the fullerene molecules is used to calculate the equilibrium position of the endohedrally atom as the minimum of the classical $(N+1)$-body Lennard-Jones potential. Once the position of the guest atom is determined, the fullerene cavity is modeled by a short range attractive shell according to molecule symmetry, and the enclosed atom is modeled by an effective one-electron potential. In order to examine whether the endohedral compound is formed by a neutral atom inside a neutral fullerene molecule $X@C_{N}$ or if the valence electron of the encapsulated atom localizes in the fullerene giving rise to a state with the form $X^{+}@C_{N}^{-}$, we analyze the electronic density, the projections onto free atomic states, and the weights of partial angular waves.

  12. Measurements of the u valence quark distribution function in the proton and u quark fragmentation functions

    International Nuclear Information System (INIS)

    A new determination of the u valence quark distribution function in the proton is obtained from the analysis of identified charged pions, kaons, protons and antiprotons produced in muon-proton and muon-deuteron scattering. The comparison with results obtained in inclusive deep inelastic lepton-nucleon scattering provides a further test of the quark-parton model. The u quark fragmentation functions into positive and negative pions, kaons, proton and antiprotons are also measured. (orig.)

  13. Measurements of the u valence quark distribution function in the proton and u quark fragmentation functions

    Science.gov (United States)

    Arneodo, M.; Arvidson, A.; Aubert, J. J.; Badelek, B.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I. G.; Blum, D.; Böhm, E.; De Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S. C.; Brück, H.; Calen, H.; Chima, J. S.; Ciborowski, J.; Clifft, R.; Coignet, G.; Combley, F.; Coughlan, J.; D'Agostini, G.; Dahlgren, S.; Dengler, F.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Edwards, M.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Gayler, J.; Geddes, N.; Grafström, P.; Grard, F.; Haas, J.; Hagberg, E.; Hasert, F. J.; Hayman, P.; Heusse, P.; Jaffre, M.; Jacholkowska, A.; Janata, F.; Jancso, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Korbel, V.; Krüger, A.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Maire, M.; Malecki, P.; Manz, A.; Maselli, S.; Mohr, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Peschel, H.; Pessard, H.; Pettingale, J.; Pietrzyk, B.; Poensgen, B.; Pötsch, M.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Sandacz, A.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Scholz, M.; Schouten, M.; Schröder, T.; Schultze, K.; Sloan, T.; Stier, H. E.; Studt, M.; Taylor, G. N.; Thenard, J. M.; Thompson, J. C.; De la Torre, A.; Toth, J.; Urban, L.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.; European Muon Collaboration

    1989-07-01

    A new determination of the u valence quark distribution function in the proton is obtained from the analysis of identified charged pions, kaons, protons and antiprotons produced in muon-proton and muon-deuteron scattering. The comparison with results obtained in inclusive deep inelastic lepton-nucleon scattering provides a further test of the quark-parton model. The u quark fragmentation functions into positive and negative pions, kaons, protons and antiprotons are also measured.

  14. The valence band electronic structure of the Cu(111) (√3X√3)R30deg-Si interface

    International Nuclear Information System (INIS)

    Full text: The structure and bonding of the copper-silicon interface is of considerable interest from a number of aspects. Firstly as a catalyst in the commercial synthesis of silane polymers, secondly as an anti-corrosion treatment, and thirdly, the formation of a well ordered and reactive silicon layer, which can be oxidised is relevant in the creation of ultra-thin silicon oxide-metal interfaces for electronic devices. Silicon is capable of forming a number of compounds with copper, the most widely studied of which is Cu3Si. Calculations have shown that when silicon impurity atoms are incorporated into a copper solid, there is an interaction between copper 3d levels and the 3s and sp levels of silicon. The silicon 2p orbitals rehybridise with the copper 3d band to form bonding and antibonding states separated by -4 eV. The resulting compounds have metallic, rather than semiconducting nature, there is charge transfer from copper to silicon and there is an increase in electron density into the silicon valence bands, making silicon more reactive. The splitting of the density of states near the Fermi edge has been measured as 4-5 eV in amorphous copper-silicon alloys, using Si Kβ fluorescence spectroscopy and has also been inferred from the 4 eV splitting of the LV V auger lines in Cu-Si compounds and in copper deposited on Si(100) and Si(111) surfaces. In this study we have used high resolution valence band photoemission spectroscopy to investigate the nature of the silicon valence bands in a well ordered silicon-copper interface. By comparing the valence band spectra of the clean surface and those from the silicon interface, we are able to identify three silicon-derived features which are in agreement with other published data. We suggest that these levels are due to emission from the 3s and 3p levels of Si

  15. Mixed valence interactions in di-μ-oxo bridged manganese complexes

    International Nuclear Information System (INIS)

    The complexes [(L)2MnO2Mn(L)2]3+ where L = 2,2'-bipyridine or 1,10-phenanthroline, have been examined, in addition to the corresponding (IV, IV) complex of phenanthroline. The crystal structure of the mixed valence (III, IV) compound with L = 2,2'-bipyridine demonstrated that this complex has deeply trapped valences, corresponding to class II in the classification of Robin and Day since the bond lengths differ considerably about the manganese ions. We have examined the electronic spectrum of the (III, IV) complexes and observed broad bands in the near infrared which we have assigned to the mixed valence band expected for a class II system. No comparable band is observed for the phenanthroline (IV, IV) complex. Lowering the pH of (III, IV) dimer solutions reversibly cleaves the antiferromagnetically coupled (III, IV) dimers as determined by the increase in solution magnetic susceptibility; loss of the near infrared band occurs with dimer cleavage, although the remainder of the visible spectrum is substantially unaltered. Both absorbance and solution magnetic susceptibility changes with pH are reversible. The solvent dependence of the near infrared band is small but apparently opposite to that predicted by Hush's theory. However, the bandwidths agree well with those predicted from Hush's treatment (e.g., 0.53 μm-1 predicted, 0.46 μm-1 observed). A band at 688 cm-1 in the infrared spectrum of the bipyridyl (III, IV) dimer is shifted by isotopic substitution with 18O, and has been assigned to one of the stretching modes of the Mn2O2 bridge; analogous bands are found for the phenanthroline (III, IV) and -(IV, IV) complexes. Pertinent aspects of the electrochemistry are also discussed

  16. Character Disposition and Behavior Type: Influences of Valence on Preschool Children's Social Judgments

    Science.gov (United States)

    Jones, Elaine F.; Tobias, Marvin; Pauley, Danielle; Thomson, Nicole Renick; Johnson, Shawana Lewis

    2009-01-01

    The authors studied the influences of valence information on preschool children's (n = 47) moral (good or bad), liking (liked or disliked by a friend), and consequence-of-behavior (reward or punishment) judgments. The authors presented 8 scenarios describing the behavior valence, positive valence (help, share), negative valence (verbal insult,…

  17. Is accessing of words affected by affective valence only? A discrete emotion view on the emotional congruency effect

    Directory of Open Access Journals (Sweden)

    Xuqian Chen

    2016-06-01

    Full Text Available This paper advances the discussion on which emotion information affects word accessing. Emotion information, which is formed as a result of repeated experiences, is primary and necessary in learning and representing word meanings. Previous findings suggested that valence (i.e., positive or negative denoted by words can be automatically activated and plays a role in many significant cognitive processes. However, there has been a lack of discussion about whether discrete emotion information (i.e., happiness, anger, sadness, and fear is also involved in these processes. According to the hierarchy model, emotions are considered organized within an abstract-to-concrete hierarchy, in which emotion prototypes are organized following affective valence. By controlling different congruencies of emotion relations (i.e., matches or mismatches between valences and prototypes of emotion, the present study showed both an evaluative congruency effect (Experiment 1 and a discrete emotional congruency effect (Experiment 2. These findings indicate that not only affective valences but also discrete emotions can be activated under the present priming lexical decision task. However, the present findings also suggest that discrete emotions might be activated at the later priming stage as compared to valences. The present work provides evidence that information about discrete emotion could be involved in word processing. This might be a result of subjects’ embodied experiences.

  18. Cerium valence change in the solid solutions Ce(Rh{sub 1-x}Ru{sub x})Sn

    Energy Technology Data Exchange (ETDEWEB)

    Niehaus, Oliver; Riecken, Jan F.; Winter, Florian; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Muenster Univ. (Germany). NRW Graduate School of Chemistry; Abdala, Paula M. [European Synchrotron Radiation Facility (ESRF), Grenoble (France). SNBL; Chevalier, Bernard [Bordeaux Univ., Pessac (France). CNRS, ICMCB

    2013-09-15

    The solid solutions Ce(Rh{sub 1-x}Ru{sub x})Sn were investigated by means of susceptibility measurements, specific heat, electrical resistivity, X-ray absorption spectroscopy (XAS), and {sup 119}Sn Moessbauer spectroscopy. Magnetic measurements as well as XAS data show a cerium valence change in dependence on the ruthenium content. Higher ruthenium content causes an increase from 3.22 to 3.45 at 300 K. Furthermore {chi} and {chi}{sup -1} data indicate valence fluctuation for cerium as a function of temperature. For example, Ce(Rh{sub 0.8}Ru{sub 0.2})Sn exhibits valence fluctuations between 3.42 and 3.32 in the temperature range of 10 to 300 K. This could be proven by using the interconfiguration fluctuation (ICF) model introduced by Sales and Wohlleben. Cerium valence change does not influence the tin atoms as proven by {sup 119}Sn Moessbauer spectroscopy, but it influences the electrical properties. Ce(Rh{sub 0.9}Ru{sub 0.1})Sn behaves like a typical valence fluctuating compound, and higher ruthenium content causes an increase of the metallic behavior. (orig.)

  19. Is Accessing of Words Affected by Affective Valence Only? A Discrete Emotion View on the Emotional Congruency Effect.

    Science.gov (United States)

    Chen, Xuqian; Liu, Bo; Lin, Shouwen

    2016-01-01

    This paper advances the discussion on which emotion information affects word accessing. Emotion information, which is formed as a result of repeated experiences, is primary and necessary in learning and representing word meanings. Previous findings suggested that valence (i.e., positive or negative) denoted by words can be automatically activated and plays a role in many significant cognitive processes. However, there has been a lack of discussion about whether discrete emotion information (i.e., happiness, anger, sadness, and fear) is also involved in these processes. According to the hierarchy model, emotions are considered organized within an abstract-to-concrete hierarchy, in which emotion prototypes are organized following affective valence. By controlling different congruencies of emotion relations (i.e., matches or mismatches between valences and prototypes of emotion), the present study showed both an evaluative congruency effect (Experiment 1) and a discrete emotional congruency effect (Experiment 2). These findings indicate that not only affective valences but also discrete emotions can be activated under the present priming lexical decision task. However, the present findings also suggest that discrete emotions might be activated at the later priming stage as compared to valences. The present work provides evidence that information about discrete emotion could be involved in word processing. This might be a result of subjects' embodied experiences. PMID:27379000

  20. A theoretical model investigation of peptide bond formation involving two water molecules in ribosome supports the two-step and eight membered ring mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qiang [School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100 (China); Gao, Jun, E-mail: gaojun@sdu.edu.cn [Agricultural Bioinformatics Key Laboratory of Hubei Province, College of Informatics, Huazhong Agricultural University, Wuhan 430070 (China); School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100 (China); Zhang, Dongju; Liu, Chengbu [School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100 (China)

    2015-04-01

    Highlights: • We theoretical studied peptide bond formation reaction mechanism with two water molecules. • The first water molecule can decrease the reaction barriers by forming hydrogen bonds. • The water molecule mediated three-proton transfer mechanism is the favorable mechanism. • Our calculation supports the two-step and eight membered ring mechanism. - Abstract: The ribosome is the macromolecular machine that catalyzes protein synthesis. The kinetic isotope effect analysis reported by Strobel group supports the two-step mechanism. However, the destination of the proton originating from the nucleophilic amine is uncertain. A computational simulation of different mechanisms including water molecules is carried out using the same reaction model and theoretical level. Formation the tetrahedral intermediate with proton transfer from nucleophilic nitrogen, is the rate-limiting step when two water molecules participate in peptide bond formation. The first water molecule forming hydrogen bonds with O9′ and H15′ in the A site can decrease the reaction barriers. Combined with results of the solvent isotope effects analysis, we conclude that the three-proton transfer mechanism in which water molecule mediate the proton shuttle between amino and carbon oxygen in rate-limiting step is the favorable mechanism. Our results will shield light on a better understand the reaction mechanism of ribosome.