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1

Valence-Bond Theory and Chemical Structure.  

ERIC Educational Resources Information Center

Discussed is the importance of valence bond theory on the quantum-mechanical theory of chemical structure and the nature of the chemical bond. Described briefly are early VB theory, development of VB theory, modern versions, solid-state applications, models, treatment in textbooks, and flaws in criticisms of valence bond theory. (KR)

Klein, Douglas J.; Trinajstic, Nenad

1990-01-01

2

Valence-bond/coherent-states approach to the charge equilibration model I. Valence-bond models for diatomic molecules.  

PubMed

A valence-bond (VB)/coherent-states (CS) approach to the charge equilibration (CE) model for diatomic molecules is presented in this work (VB part) and its sequel (CS part). By emphasizing theoretical aspects, this approach obtains the classical-electrostatics CE model from a quantum VB model in conjunction with the CS theory. For the VB part, a VB generalized CE (VB/GCE) model, which contains the CE model as a subcase, is derived from a two-electron, three-state VB model via the sequential application of seven approximations. Unlike its CE subcase, the VB/GCE model provides a satisfactory charge-transfer description at dissociation as illustrated with HF((g)) and other molecules. Through the previous derivation, CE charges and CE Coulomb interactions are elucidated in terms of VB Mulliken charges and VB atomic interactions, respectively. Modifications in the above derivation can generate a family of related VB/GCE models that includes the aforesaid VB/GCE model. Despite their classical appearance, all of the VB/GCE and CE models involve VB wave functions corresponding to ground and first-excited states. Moreover, all of the VB/GCE and CE energy and charge optimizations are proven to be equivalent to the variational eigenvector equation procedures of the underlying VB models. The quantum-mechanics/classical-electrostatics connection implicit in this work is further elaborated by means of VB CS sets in the sequel. The VB/CS treatment of polyatomic molecules and additional tests of the present approach will be reported in later papers in this series. PMID:19391590

Morales, Jorge A

2009-05-21

3

The valence bond glass phase  

NASA Astrophysics Data System (ADS)

We show that a new glassy phase can emerge in the presence of strong magnetic frustration and quantum fluctuations. It is a valence bond glass (VBG). We study its properties solving the Hubbard-Heisenberg model on a Bethe lattice within the large-N limit introduced by Affleck and Marston. We work out the phase diagram that contains Fermi liquid, dimer and valence bond glass phases. This new glassy phase has no electronic or spin gap (although a pseudo-gap is observed), it is characterized by long-range critical valence bond correlations and is not related to any magnetic ordering. As a consequence, it is quite different from both valence bond crystals and spin glasses.

Tarzia, M.; Biroli, G.

2008-06-01

4

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

ERIC Educational Resources Information Center

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…

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

2008-01-01

5

How valence bond theory can help you understand your (bio)chemical reaction.  

PubMed

Almost a century has passed since valence bond (VB) theory was originally introduced to explain covalent bonding in the H2 molecule within a quantum mechanical framework. The past century has seen constant improvements in this theory, with no less than two distinct Nobel prizes based on work that is essentially developments in VB theory. Additionally, ongoing advances in both methodology and computational power have greatly expanded the scope of problems that VB theory can address. In this Tutorial Review, we aim to give the reader a solid understanding of the foundations of modern VB theory, using a didactic example of a model SN2 reaction to illustrate its immediate applications. This will be complemented by examples of challenging problems that at present can only be efficiently addressed by VB-based approaches. Finally, the ongoing importance of VB theory is demonstrated. It is concluded that VB will continue to be a major driving force for chemistry in the century to come. PMID:25352378

Shurki, Avital; Derat, Etienne; Barrozo, Alexandre; Kamerlin, Shina Caroline Lynn

2014-10-29

6

When valence bond wave functions are analyzed through QTAIM: Conceptual incompatibilities in H2  

NASA Astrophysics Data System (ADS)

Hydrogen molecule was chosen, for simplicity, to analyze its valence bond (VB) wave function with the Quantum Theory of Atoms in Molecules (QTAIM). We find that the usual association of its covalent and ionic contributions to individual Lewis structures does not agree with the localization and delocalization indices between both hydrogens defined within the QTAIM framework. Concretely, we analyzed the dependence of both indices with the internuclear distance and with different ionic/covalent relative weightings. The results indicate that QTAIM localization and delocalization indices should not be estimated from interpretations of the VB wave function in terms of the Lewis model.

Ferro-Costas, David; Mosquera, Ricardo A.

2015-01-01

7

Valence-Bond Monte Carlo Study of Random-Singlet Phase Formation  

NASA Astrophysics Data System (ADS)

In valence-bond Monte Carlo (VBMC)ootnotetextA. Sandvik, PRL 95, 207203 (2005). the ground state of a quantum spin system is sampled directly from the valence-bond (VB) basis --- a useful basis for visualizing the properties of singlet ground states. For example, the ground state of the uniform AFM spin-12 Heisenberg chain is characterized by strongly fluctuating bonds with power-law length distribution, while in the random-singlet phase (RSP) of a random Heisenberg chain these bonds, while still having a power-law length distribution, lock into a particular VB state on long length scales.ootnotetextD. S. Fisher, PRB 50, 3799 (1994). We use VBMC to directly probe the formation of a RSP by calculating both the average number of bonds nL leaving a block of L spins (the VB entanglement entropyootnotetextF. Alet, et al., PRL 99, 117204 (2007).), and its fluctuations, ?nL^2 = <- . For the uniform chain they have been calculated exactlyootnotetextJ. L. Jacobsen and H. Saleur, PRL 100, 087205 (2008). and shown to grow logarithmically with L --- signaling the strong bond fluctuations. For random chains while nL grows logarithmically with L, we find ?nL^2 saturate for large L, signaling the ``freezing" of the bonds into a particular random singlet state.

Tran, Huan; Bonesteel, Nicholas

2009-03-01

8

VBEFP: a valence bond approach that incorporates effective fragment potential method.  

PubMed

An ab initio explicit solvation valence bond (VB) method, called VBEFP, is presented. The VBEFP method is one type of QM/MM approach in which the QM part of system is treated within the ab initio valence bond scheme and the solvent water molecules are accounted by the effective fragment potential (EFP) method, which is a polarized force field approach developed by Gordon et al. (J. Chem. Phys. 1996, 105, 1968). This hybrid method enables one to take the first-solvation shell and heterogeneous solvation effects into account explicitly with VB wave function. Therefore, the nature of chemical bonding and the mechanism of chemical reactions with explicit solvent environments can be explored at the ab inito VB level. In this paper, the hydrated metal-ligand complexes [M(2+)L](H(2)O)(n) (M(2+): Mg(2+), Zn(2+); L: NH(3), CH(2)O) are studied by the VBEFP method. Resonance energy and bond order are computed, and the influence of the solvent coordination and hydrogen bonding to the metal-ligand bonding are explored in the paper. PMID:22276645

Ying, Fuming; Chang, Xin; Su, Peifeng; Wu, Wei

2012-02-23

9

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  

NASA Astrophysics Data System (ADS)

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.

Chen, Zhenhua; Chen, Xun; Wu, Wei

2013-04-01

10

Delocalization in valence bond-Hyperconjugation  

NASA Astrophysics Data System (ADS)

We consider delocalization in small molecules. The valence bond technology allows an arbitrary division of the 1-electron space in strictly separate, but nonorthogonal, spaces. Allowing or obstructing orbital mixing between subspaces during the SCF procedure is associated with incorporating or eliminating the hyperconjugation effect. We show an example for tert-butyl and trimethylsilyl cations and radicals. For H2, for which really extensive basis sets are feasible, we extend the basis so far that the delocalization or hyperconjugation effect has nearly disappeared.

Havenith, R. W. A.; van Lenthe, J. H.

11

Reinterpretation of the bond-valence model with bond-order formalism: An improved bond-valence-based interatomic potential for PbTiO3  

NASA Astrophysics Data System (ADS)

We present a modified bond-valence model of PbTiO3 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. An energy term, bond-valence vector energy, is introduced into the atomistic model and the potential parameters are reoptimized. This model potential can be applied both to canonical-ensemble (NVT) and isobaric-isothermal ensemble (NPT) molecular dynamics (MD) simulations. This model reproduces the experimental phase transition in NVT MD simulations and also exhibits the experimental sequence of temperature-driven and pressure-driven phase transitions in NPT simulations. We expect that this improved bond-valence model can be applied to a broad range of inorganic materials.

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

2013-09-01

12

Bond-valence methods for pKa prediction. II. Bond-valence, electrostatic, molecular geometry, and solvation effects  

SciTech Connect

In a previous contribution, we outlined a method for predicting (hydr)oxy-acid and oxide surface acidity constants based on three main factors: bond valence, Me?O bond ionicity, and molecular shape. Here electrostatics calculations and ab initio molecular dynamics simulations are used to qualitatively show that Me?O bond ionicity controls the extent to which the electrostatic work of proton removal departs from ideality, bond valence controls the extent of solvation of individual functional groups, and bond valence and molecular shape controls local dielectric response. These results are consistent with our model of acidity, but completely at odds with other methods of predicting acidity constants for use in multisite complexation models. In particular, our ab initio molecular dynamics simulations of solvated monomers clearly indicate that hydrogen bonding between (hydr)oxo-groups and water molecules adjusts to obey the valence sum rule, rather than maintaining a fixed valence based on the coordination of the oxygen atom as predicted by the standard MUSIC model.

Bickmore, Barry R.; Rosso, Kevin M.; Tadanier, Christopher J.; Bylaska, Eric J.; Doud, Darrin

2006-08-15

13

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

PubMed Central

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 coordination was evaluated. Results show the AMOEBA-VB model generates the correct square-planar geometry for gas phase tetra-aqua Cu2+ 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 Zn2+-water complexes in good agreement with QM calculations. Analyses of the MD trajectories revealed a 6-coordination first solvation shell for both Cu2+ and Zn2+ ions in aqueous solution, with ligation geometries falling in the range reported by previous studies. PMID:23212979

Xiang, Jin Yu; Ponder, Jay W.

2013-01-01

14

Topological Structure of Phase Vortex in Resonating Valence Bond Superconductivity  

NASA Astrophysics Data System (ADS)

In this paper, based on the Schrödinger equation and the ?-mapping theory, the accurate expression for the gradient of resonating valence bond superconducting phase ?s is found. The expression of vec nabla?s is just the velocity flow vec V without considering the coefficient. The curl of vec nabla?s is where the vortex lies, and has important relation to ?2(?) and an important relation to the zero points of resonating valence bond superconducting order parameter ?. The topological structure of the vortex is characterized by the ?-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.

Shi, Xu-Guang; Duan, Yi-Shi

2006-07-01

15

Resonating valence-bond physics on the honeycomb lattice  

NASA Astrophysics Data System (ADS)

We study bond and spin correlations of the nearest-neighbor resonating valence bond (RVB) wave function for a SU(2) symmetric S =1 /2 antiferromagnet on the honeycomb lattice. We find that spin correlations in this wave function are short ranged, while the bond energy correlation function takes on an oscillatory power-law form D (r ?) ˜cos(Q .r ?) /|r?| ?w(2 ) , where Q =(2 ? /3 ,-2 ? /3 ) is the wave vector corresponding to "columnar" valence-bond solid order on the honeycomb lattice, and ?w(2 ) ?1.49 (3 ) . We use a recently introduced large-g expansion approach to relate bond-energy correlators of the SU (g ) wave function to dimer correlations of an interacting fully packed dimer model with a three-dimer interaction of strength V (g ) =-ln(1 +1 /g2) . Putting g =2 , we find numerically that the dimer correlation function Dd(r ?) of this dimer model has power-law behavior Dd(r ?) ˜cos(Q .r ?) /|r?| ?d(2 ) with ?d(2 ) ?1.520 (15 ) , in rather good agreement with the wave function results. We also study the same quantities for g =3 ,4 ,10 and find that the bond-energy correlations in the SU (g ) wave function are consistently well reproduced by the corresponding dimer correlations in the interacting dimer model.

Patil, Pranay; Dasgupta, Ishita; Damle, Kedar

2014-12-01

16

Connections between coupled cluster and generalized valence bond theories  

NASA Astrophysics Data System (ADS)

We explore the fundamental connections between certain approximate coupled cluster (CC) and generalized valence bond (GVB) wave functions. We show that the GVB restricted configuration interaction (GVB-RCI) wave function can be associated with a compact CC expansion in the valence space. However, careful analysis reveals that a standard CC expansion contains terms that are not contained in the GVB-RCI wave function. The offending terms violate an effective pairwise exclusion principle (PEP) that is present in the RCI expansion, but is not enforced in the CC analog. These terms do not affect the size separability of either method. Variational calculations show noticeable improvements to the CC wave function when the PEP is enforced, with the most significant improvements coming near the dissociation limit. We modify the standard CC amplitude equations by removing the PEP violating terms and demonstrate remarkably improved results for the dissociation of N2 and the double dissociation of H2O.

Van Voorhis, Troy; Head-Gordon, Martin

2001-11-01

17

Valence-bond quantum Monte Carlo algorithms defined on trees  

NASA Astrophysics Data System (ADS)

We present a class of algorithms for performing valence-bond quantum Monte Carlo of quantum spin models. Valence-bond quantum Monte Carlo is a projective T =0 Monte Carlo method based on sampling of a set of operator strings that can be viewed as forming a treelike structure. The algorithms presented here utilize the notion of a worm that moves up and down this tree and changes the associated operator string. In quite general terms, we derive a set of equations whose solutions correspond to a whole class of algorithms. As specific examples of this class of algorithms, we focus on two cases. The bouncing worm algorithm, for which updates are always accepted by allowing the worm to bounce up and down the tree, and the driven worm algorithm, where a single parameter controls how far up the tree the worm reaches before turning around. The latter algorithm involves only a single bounce where the worm turns from going up the tree to going down. The presence of the control parameter necessitates the introduction of an acceptance probability for the update.

Deschner, Andreas; Sørensen, Erik S.

2014-09-01

18

Valence-bond quantum Monte Carlo algorithms defined on trees.  

PubMed

We present a class of algorithms for performing valence-bond quantum Monte Carlo of quantum spin models. Valence-bond quantum Monte Carlo is a projective T=0 Monte Carlo method based on sampling of a set of operator strings that can be viewed as forming a treelike structure. The algorithms presented here utilize the notion of a worm that moves up and down this tree and changes the associated operator string. In quite general terms, we derive a set of equations whose solutions correspond to a whole class of algorithms. As specific examples of this class of algorithms, we focus on two cases. The bouncing worm algorithm, for which updates are always accepted by allowing the worm to bounce up and down the tree, and the driven worm algorithm, where a single parameter controls how far up the tree the worm reaches before turning around. The latter algorithm involves only a single bounce where the worm turns from going up the tree to going down. The presence of the control parameter necessitates the introduction of an acceptance probability for the update. PMID:25314561

Deschner, Andreas; Sørensen, Erik S

2014-09-01

19

Hybrid valence-bond states for universal quantum computation  

NASA Astrophysics Data System (ADS)

The spin-3/2 Affleck-Kennedy-Lieb-Tasaki (AKLT) valence-bond state on a hexagonal lattice was shown to be a universal resource state for measurement-based quantum computation (MBQC). Can AKLT states of higher spin magnitude support universal MBQC? We demonstrate that several hybrid two-dimensional AKLT states involving a mixture of spin-2 and other lower-spin entities, such as spin-3/2 and spin-1, are also universal for MBQC. This significantly expands universal resource states in the AKLT family. Even though frustration may be a hindrance to quantum computational universality, lattices can be modified to yield AKLT states that are universal. The family of AKLT states thus provides a versatile playground for quantum computation.

Wei, Tzu-Chieh; Haghnegahdar, Poya; Raussendorf, Robert

2014-10-01

20

Topological and entanglement properties of resonating valence bond wave functions  

NASA Astrophysics Data System (ADS)

We examine in details the connections between topological and entanglement properties of short-range resonating valence bond (RVB) wave functions using projected entangled pair states (PEPS) on kagome and square lattices on (quasi)infinite cylinders with generalized boundary conditions (and perimeters with up to 20 lattice spacings). By making use of disconnected topological sectors in the space of dimer lattice coverings, we explicitly derive (orthogonal) “minimally entangled” PEPS RVB states. For the kagome lattice, using the quantum Heisenberg antiferromagnet as a reference model, we obtain the finite-size scaling with increasing cylinder perimeter of the vanishing energy separations between these states. In particular, we extract two separate (vanishing) energy scales corresponding (i) to insert a vison line between the two ends of the cylinder and (ii) to pull out and freeze a spin at either end. We also investigate the relations between bulk and boundary properties and show that, for a bipartition of the cylinder, the boundary Hamiltonian defined on the edge can be written as a product of a highly nonlocal projector, which fundamentally depends upon boundary conditions, with an emergent (local) SU(2)-invariant one-dimensional (superfluid) t-J Hamiltonian, which arises due to the symmetry properties of the auxiliary spins at the edge. This multiplicative structure, a consequence of the disconnected topological sectors in the space of dimer lattice coverings, is characteristic of the topological nature of the states. For minimally entangled RVB states, it is shown that the entanglement spectrum, which reflects the properties of the (gapless or gapped) edge modes, is a subset of the spectrum of the local Hamiltonian, e.g., half of it for the kagome RVB state, providing a simple argument on the origin of the topological entanglement entropy S0=-ln2 of the Z2 spin liquid. We propose to use these features to probe topological phases in microscopic Hamiltonians, and some results are compared to existing density matrix renormalization group data.

Poilblanc, Didier; Schuch, Norbert; Pérez-García, David; Cirac, J. Ignacio

2012-07-01

21

Bond-valence model for metal cluster compounds. II. Matrix effect.  

PubMed

The bond-valence model was commonly considered as inappropriate to metal cluster compounds, but recently it was shown that the model provides unique information on the lattice strains and stabilization mechanisms in (TM)6-chalcohalides, Mx(TM)6Ly (TM = transition metal, L = the chalcogen and/or halogen ligands; M = counter-cation). The previous study was mainly devoted to the non-uniform distribution of the anion valences (bond-valence sums) around clusters. This and the previous paper are focused on two additional phenomena: (i) a steric conflict between counter-cations and the cluster-ligand framework resulting in `common' lattice strains [previous paper: Levi et al. (2013). Acta Cryst. B69, 419-425], and (ii) steric conflict between the small (TM)6-cluster and the large coordination polyhedron around the cluster or so-called matrix effect (this paper). It was shown that both phenomena can be well described by changes in the bond-valence parameters. This paper demonstrates that the matrix effect results in high strains in the TM-L bonds in most of the (TM)6-chalcohalides (TM = Nb, Mo, W and Re). In spite of this, the violations for the total TM valence are minimal, because the cluster stretching is fully or partially compensated by compression of the TM-L bonds. As a result, the influence of the matrix effect on the material stability is rather positive: it decreases the volume of the structural units and in many cases ensures a more favorable distribution of the bond valences around TM atoms, stabilizing the cluster compound. PMID:24056351

Levi, Elena; Aurbach, Doron; Isnard, Olivier

2013-10-01

22

Stoichiometric Valence and Structural Valence--Two Different Sides of the Same Coin: "Bonding Power"  

E-print Network

that chemical compounds contain elements in certain weight or atom ratios. For exam- ple, in NH3, PH3, AsH3 and SbH3, one pnictide atom is equivalent to three hydrogen atoms and one mole of a pnic- tide is equivalent to three moles of hydrogen. The property of an atom to compensate the bonding power of an equiva

Wang, Xiqu

23

Nitrobenzene valence bond structures: evidence in support of ''through-resonance'' from /sup 17/O shieldings  

SciTech Connect

/sup 17/O shieldings in nitrobenzenes have been found to be sensitive to the electronic character of para substituents precisely in the manner anticipated from consideration of valence bond structure. Furthermore, the large sensitivity to electron density changes indicates /sup 17/O to be an attractive probe of electron distributions.

Fraser, R.R. (Univ. of Ottawa, Ontario, Canada); Ragauskas, A.J.; Stothers, J.B.

1982-11-17

24

Bond-valence model for metal cluster compounds. I. Common lattice strains.  

PubMed

The bond-valence model was commonly considered as inappropriate to metal cluster compounds, but recently it was shown that the model provides unique information on the lattice strains and stabilization mechanisms in (TM)6-chalcohalides (TM = transition metal in the cluster). The previous study was mainly devoted to the non-uniform distribution of the anion valences (bond-valence sums) around clusters. This and the following paper focuses on two additional phenomena: (i) a steric conflict between counter-cations and the cluster-ligand framework resulting in `common' lattice strains (this paper), and (ii) steric conflict between the small (TM)6-cluster and the large coordination polyhedron around the cluster or so-called matrix effect [the next paper; Levi et al. (2013), Acta Cryst. B69, 426-438]. It was shown that both phenomena can be well described by changes in the bond-valence parameters. The calculations were based on the structural data known to date for a variety of (TM)6-cluster compounds, Mx(TM)6Ly (TM = Nb, Mo, W and Re; M = various additional cations, L = the chalcogen and/or halogen ligands). The results were used to explain the structural peculiarities of these compounds with remarkable physical properties and the mechanisms of their stabilization. PMID:24056350

Levi, Elena; Aurbach, Doron; Isnard, Olivier

2013-10-01

25

Frustrated magnetism and resonating valence bond physics in two-dimensional kagome-like magnets  

NASA Astrophysics Data System (ADS)

We explore the phase diagram and the low-energy physics of three Heisenberg antiferromagnets which, like the kagome lattice, are networks of corner-sharing triangles but contain two sets of inequivalent short-distance resonance loops. We use a combination of exact diagonalization, analytical strong-coupling theories, and resonating valence bond approaches, and scan through the ratio of the two inequivalent exchange couplings. In one limit, the lattices effectively become bipartite, while at the opposite limit heavily frustrated nets emerge. In between, competing tunneling processes result in short-ranged spin correlations, a manifold of low-lying singlets (which can be understood as localized bound states of magnetic excitations), and the stabilization of valence bond crystals with resonating building blocks.

Rousochatzakis, Ioannis; Moessner, Roderich; van den Brink, Jeroen

2013-11-01

26

Resonating valence bond state in LaâCuOâ and superconductivity  

Microsoft Academic Search

The oxide superconductors, particularly those recently discovered that are based on LaâCuOâ, have a set of peculiarities that suggest a common, unique mechanism: they tend in every case to occur near a metal-insulator transition into an odd-electron insulator with peculiar magnetic properties. This insulating phase is proposed to be the long-sought resonating-valence-bond state or quantum spin liquid hypothesized in 1973.

P. W. ANDERSON

1987-01-01

27

Valence bond solid formalism for d-level one-way quantum computation  

Microsoft Academic Search

The d-level or qudit one-way quantum computer (d1WQC) is described using the valence bond solid formalism and the generalized Pauli group. This formalism provides a transparent means of deriving measurement patterns for the implementation of quantum gates in the computational model. We introduce a new universal set of qudit gates and use it to give a constructive proof of the

Sean Clark

2006-01-01

28

Consistent theory of underdoped cuprates: Evolution of the resonating valence bond state from half filling  

NASA Astrophysics Data System (ADS)

Using continuity, we derive a renormalized Hamiltonian from the parent t-J model to describe the properties of underdoped cuprates. The theory is constrained to agree with the behavior at half filling, which is well described by the Arovas-Auerbach valence bond state in which bosonic spinons are paired into singlets. Spinon states evolve continuously into the doped region preserving their symmetry. We assume that moving holes rapidly destroy magnetic order, which leads to a gap in the spinon spectrum and strongly renormalizes the theory. The spin gap leads to two different types hopping terms for renormalized holes. In one, a fermionic holon hops within the same sublattice accompanied by a singlet backflow, giving rise to a non-Fermi-liquid normal state with novel properties. Spinon singlets condense below a pseudogap temperature T? ( < spin gap temperature T0 ), which allows holons to propagate coherently, forming a spinless Fermi liquid, but without an observable holon Fermi surface. Above T? , holons are localized. This is the so-called strange metal phase, which is actually a new type of insulator since its resistivity would be infinite at T=0 . In the second term a pair of holons belonging to opposite sublattices hop, accompanied by a singlet backflow. In the presence of the singlet condensate holon pairs condense, leading to d -wave superconductivity; the symmetry is primarily determined by the symmetry of the valence bond state at half filling. The metal and the superconductor preserve the two-sublattice character of the valence bond state. A careful examination of the nuclear magnetic resonance, tunneling, and transport data shows that the predictions of the theory is consistent with experimental results. Remarkably, the existence of the spin gap provides a natural explanation for the phenomenon of two dimensionality of the normal state in the presence of interplane hopping. The marked asymmetry between hole-doped and electron-doped cuprates is also easily explained.

Sarker, Sanjoy K.; Lovorn, Timothy

2010-07-01

29

Electronic bond rupture of Si atoms on Si(111)-(2×1) induced by valence excitation  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy study reveals the electronic local bond rupture of threefold-coordinated Si atoms at intrinsic sites on Si(111)-(2×1) under nanosecond-laser excitation at 1064nm . The rate of bond rupture leading to monovacancy formation on the surface depends superlinearly on the excitation intensity. This primary step of surface-structural change is followed by efficient formation of vacancy clusters with two distinctive morphologies: vacancy strings aligned along the Si-atom chain in one dimension and vacancy islands developed across the chains in two dimensions. Quantitative analysis of the vacancy clustering process shows that the bond-rupture rate at sites nearest to pre-existing surface defects is enhanced more than a factor of 1000 relative to perfect sites. We also studied effects of different excitation wavelength and of Fermi-level positions on the bond-rupture process. The laser-induced surface bond-rupture mechanism is discussed in terms of two-hole localization of optically generated nonequilibrated valence holes on the surface sites.

Inami, E.; Tanimura, K.

2007-07-01

30

Valence-Bond Monte Carlo for Chains of Non-Abelian Quasiparticles  

NASA Astrophysics Data System (ADS)

In non-Abelian FQH states, quasiparticles carry quantum numbers (topological charge) which characterize a degenerate Hilbert space. When these quasiparticles are close enough together, the degeneracy of this Hilbert space is lifted and the quasiparticles are said to interact. Here we show that the valence-bond Monte Carlo method introduced by Sandvik for spin-1/2 systems can be generalized to simulate 1D chains of such interacting non-Abelian quasiparticles. For uniform chains, our Monte Carlo results for the ground state energy agree with known exact values.^1 For random chains we confirm numerically that, as expected, the ground state freezes into a random singlet phase. By suitably generalizing the notion of valence-bond entanglement entropy to the non-Abelian case we also confirm the predicted result^3 that in this phase the entropy of a block of length L scales as S^VBL˜d3 2L, where d is the quantum dimension of the quasiparticles. Work supported by US DOE.

Tran, Huan; Bonesteel, Nick

2008-03-01

31

Emergence of Superconductivity, Valence Bond Order, and Mott Insulators in Pd[(dmit)2] Based Organic Salts  

NASA Astrophysics Data System (ADS)

The EtMe3P and EtMe3Sb triangular organic salts are distinguished from 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 reentrant transition of insulator-metal-insulator type can be explained by an entropy difference between the metal and U(1) spin liquid. We predict different temperature dependence of the specific heat between the spin liquid and metal.

Rau, Jeffrey G.; Kee, Hae-Young

2011-02-01

32

Nonorthogonal orbital based N-body reduced density matrices and their applications to valence bond theory. II. An efficient algorithm for matrix elements and analytical energy gradients in VBSCF method  

NASA Astrophysics Data System (ADS)

In this paper, by applying the reduced density matrix (RDM) approach for nonorthogonal orbitals developed in the first paper of this series, efficient algorithms for matrix elements between VB structures and energy gradients in valence bond self-consistent field (VBSCF) method were presented. Both algorithms scale only as nm4 for integral transformation and d^2 n_? ^2 for VB matrix elements and 3-RDM evaluation, while the computational costs of other procedures are negligible, where n, m, d, and n? are the numbers of variable occupied active orbitals, basis functions, determinants, and active ? electrons, respectively. Using tensor properties of the energy gradients with respect to the orbital coefficients presented in the first paper of this series, a partial orthogonal auxiliary orbital set was introduced to reduce the computational cost of VBSCF calculation in which orbitals are flexibly defined. Test calculations on the Diels-Alder reaction of butadiene and ethylene have shown that the novel algorithm is very efficient for VBSCF calculations.

Chen, Zhenhua; Chen, Xun; Wu, Wei

2013-04-01

33

Competing valence-bond states of spin-3/2 fermions on a strongly coupled ladder  

NASA Astrophysics Data System (ADS)

We study the possible ground-state configurations of two strongly coupled chains of charge neutral spin-3/2 fermionic atoms interacting via short-range van der Waals interaction. The coupling between the two chains is realized by a relatively large hopping amplitude. Exploiting the fact that such a ladder configuration can be mapped to an effective one-band model, we analyze the emerging ground states of the system. We show that various spatially inhomogeneous states, valence-bond states, and plaquette states compete depending on the filling and the ratio of the interaction strengths in the singlet and quintet scattering channel. We find that a Luttinger liquid state is the ground state of the strongly coupled ladder in an extended region of the parameter space, and we also show that a topologically nontrivial charge Haldane state can emerge in the strongly coupled ladder at quarter and three-quarter fillings.

Szirmai, E.; Nonne, H.

2014-12-01

34

Resonating valence bond state in La/sub 2/CuO/sub 4/ and superconductivity  

SciTech Connect

The oxide superconductors, particularly those recently discovered that are based on La/sub 2/CuO/sub 4/, have a set of peculiarities that suggest a common, unique mechanism: they tend in every case to occur near a metal-insulator transition into an odd-electron insulator with peculiar magnetic properties. This insulating phase is proposed to be the long-sought resonating-valence-bond state or quantum spin liquid hypothesized in 1973. This insulating magnetic phase is favored by low spin, low dimensionality, and magnetic frustration. The preexisting magnetic singlet pairs of the insulating state become charged superconducting pairs when the insulator is doped sufficiently strongly. The mechanism for superconductivity is hence predominantly electronic and magnetic, although weak phonon interactions may favor the state. Many unusual properties are predicted, especially of the insulating state.

Anderson, P.W.

1987-03-06

35

A comparison of Car—Parrinello and Born—Oppenheimer generalized valence bond molecular dynamics  

NASA Astrophysics Data System (ADS)

Two methods for performing ab initio molecular dynamics using a generalized valence bond electronic wave function are compared: the Car—Parrinello and Born—Oppenheimer approaches. These techniques differ in how they generate a new electronic wave function at each time step. In the Car—Parrinello scheme, the wave function parameters are propagated as classical degrees of freedom, while in the Born—Oppenheimer scheme the equations describing the wave function are solved at each time step. It is found that trajectories obtained utilizing the Born—Oppenheimer approach are both more accurate and less costly than their Car—Parrinello counterparts for wave functions expressed in terms of atom-centered basis sets.

Gibson, Douglas A.; Ionova, Irina V.; Carter, Emily A.

1995-06-01

36

Valence-dependent analytic bond-order potential for transition metals  

NASA Astrophysics Data System (ADS)

An analytic interatomic bond-order potential is derived that depends explicitly on the valence of the transition-metal element. It generalizes the second-moment Finnis-Sinclair and fourth-moment Carlsson potentials to include higher moments. We find that the sixth-moment approximation predicts not only the structural trend from hcp?bcc?hcp?fcc that is observed across the nonmagnetic 4d and 5d transition-metal series, but also the different ferromagnetic moments of the bcc, fcc, and hcp phases of the 3d transition-metal iron. An analytic expression for the force is obtained and proved to converge to the Hellmann-Feynman force as higher moments are included.

Drautz, Ralf; Pettifor, D. G.

2006-11-01

37

Orbitals that are unrestricted in active pairs for generalized valence bond coupled cluster methods.  

PubMed

Spin unrestriction is typically defined as a free variation of the molecular orbitals of different spins in order to lower the molecular energy. When applied to approximate active space electron correlation methods, such as generalized valence bond coupled cluster (GVB-CC) models, this approach often leads to undesirable artifacts. We therefore present an alternative unrestricted in active pairs (UAP) procedure for spin polarization in GVB-CC methods, which resembles the corresponding orbitals of unrestricted Hartree-Fock theory. The UAP procedure permits spin polarization only within the two orbital subspaces describing each electron pair (consisting of one nominally occupied and one virtual orbital). This great reduction to just a linear number of degrees of freedom associated with spin polarization eliminates many of the undesirable artifacts associated with unconstrained spin unrestriction. The UAP procedure is tested on a variety of potential curves for bond breaking and the properties of small radicals as well as larger polyenyl radicals, allyl, pentadienyl, and heptatrienyl. PMID:20141227

Lawler, Keith V; Small, David W; Head-Gordon, Martin

2010-03-01

38

Resonating valence bond trial wave functions with both static and dynamically determined Marshall sign structure  

NASA Astrophysics Data System (ADS)

We construct energy-optimized resonating valence bond wave functions as a means to sketch out the zero-temperature phase diagram of the square-lattice quantum Heisenberg model with competing nearest- (J1) and next-nearest-neighbor (J2) interactions. Our emphasis is not on achieving an accurate representation of the magnetically disordered intermediate phase (centered on a relative coupling g=J2/J1˜(1)/(2) and whose exact nature is still controversial) but on exploring whether and how the Marshall sign structure breaks down in the vicinity of the phase boundaries. Numerical evaluation of two- and four-spin correlation functions is carried out stochastically using a worm algorithm that has been modified to operate in either of two modes: one in which the sublattice labeling is fixed beforehand and another in which the worm manipulates the current labeling so as to sample various sign conventions. Our results suggest that the disordered phase evolves continuously out of the (?,?) Néel phase and largely inherits its Marshall sign structure; on the other hand, the transition from the magnetically ordered (?,0) phase is strongly first order and involves an abrupt change in the sign structure and spatial symmetry as the result of a level crossing.

Zhang, Xiaoming; Beach, K. S. D.

2013-03-01

39

Signatures of spin-triplet excitations in optical conductivity of valence bond solids  

NASA Astrophysics Data System (ADS)

We show that the optical responses below the Mott gap can be used to probe the spin-triplet excitations in valence bond solid (VBS) phases in Mott insulators. The optical conductivity in this regime arises due to the electronic polarization mechanism via virtual electron-hopping processes. We apply this mechanism to the Hubbard model with spin–orbit couplings and/or the corresponding spin model with significant Dzyaloshinskii–Moriya (DM) interactions, and compute the optical conductivity of VBS states on both ideal and deformed Kagome lattices. In the case of the deformed Kagome lattice, we study the antiferromagnet Rb2Cu3SnF12 with the pinwheel VBS state. In case of the ideal Kagome lattice, we explore the optical conductivity signatures of the spin-triplet excitations for three VBS states with (1) a 12-site unit cell, (2) a 36-site unit cell with six-fold rotation symmetry, and (3) a 36-site unit cell with three-fold rotation symmetry, respectively. We find that increasing the DM interactions generally leads to broad and smooth features in the optical conductivity with interesting experimental consequences. The optical conductivity reflects the features of the spin-triplet excitations that can be measured in future experiments.

Hwang, Kyusung; Bhattacharjee, Subhro; Kim, Yong Baek

2014-12-01

40

Destruction of valence-bond order in a S=(1)/(2) sawtooth chain with a Dzyaloshinskii-Moriya term  

NASA Astrophysics Data System (ADS)

A small value of the spin gap in quantum antiferromagnets with strong frustration makes them susceptible to nominally small deviations from the ideal Heisenberg model. One such perturbation, the anisotropic Dzyaloshinskii-Moriya (DM) interaction, is an important perturbation for the S=1/2 kagome antiferromagnet, one of the current candidates for a quantum-disordered ground state. We study the influence of the DM term in a related one-dimensional system, the sawtooth chain, which has valence-bond order in its ground state. Through a combination of analytical and numerical methods, we show that a relatively weak DM coupling, 0.115J, is sufficient to destroy the valence-bond order, close the spin gap, and turn the system into a Luttinger liquid with algebraic spin correlations. A similar mechanism may be at work in the kagome antiferromagnet.

Hao, Zhihao; Wan, Yuan; Rousochatzakis, Ioannis; Wildeboer, Julia; Seidel, A.; Mila, F.; Tchernyshyov, O.

2011-09-01

41

Thermochemical considerations and bond enthalpy ratios involving triatomic 16-valence electron neutrals and ions and some isoelectronically related pentaatomics  

Microsoft Academic Search

Following thermochemical studies and the accompanying analysis in the calorimetric literature, in earlier computational and conceptual studies we investigated the systematics of the mean bond enthalpy ratio ?Dm°(XY2)?\\/Dm°(XY) for 16-valence electron neutral and ionic triatomic species. For neutral species wherein X is a group 14 element and Y is from group 16, the ratio was ca. 0.8 rising to ca.

Carol A. Deakyne; Lisa K. Norton; Ashley M. Abele; Alicia K. Ludden; Joel F. Liebman

2007-01-01

42

Multi-state empirical valence bond MD modeling of hydroxyl ion transfer in aqueous environments  

NASA Astrophysics Data System (ADS)

Physical and chemical properties of mineral-water interfaces control many important geochemical and environmental processes, such as mineral weathering and soil development, surface ion adsorption and ion exchange, the mobility of contaminants in surface and groundwater systems, and removal and sequestration of atmospheric CO2. The interaction of water with minerals can substantially affect the properties of both phases, including the structure and dynamics of the interfacial water films and the reactivity and functionality of the substrate surface. These mineral-water interactions are principally controlled by the substrate structure, composition and surface charge distribution, which widely vary among minerals. However, the surfaces of most oxides are well-known to be hydroxylated in contact with liquid water or with atmospheric water vapor at normal relative humidities. Thus, the mineral surface chemistry of common oxides, hydroxides and silicates of the Earth's near-surface environment is strongly affected by the pH dependent reactions of protonation/deprotonation. Local electron density variations due to structural substitutions or defects can also provide negatively or positively charged surface sites that can significantly influence the structure and dynamics of the interfacial hydrogen bonding network and catalyze the protonation/deprotonation reactions at the surface. With the ultimate goal of developing quantitatively accurate molecular models of reactive mineral surfaces, we present here first results for the simplest system that exhibits water-hydroxide proton transfer: a single OH^- ion in liquid water. We have modeled proton transfer in this system with molecular dynamics (MD) simulation using the multi-state empirical valence bond approach (MS-EVB), in which the classical Newtonian equations of motion are integrated using a specifically developed MS-EVB force field. The empirical parameters of the EVB Hamiltonian matrix elements are fitted to reproduce the potential energy surface of the H3O2^- molecule as well as the geometries and energies of small (H2O)_nOH^- clusters calculated by ab- initio methods at the RHF 6-31G**/MP2 level with a conductor-like screening model (COSMO). The COSMO model mimics the presence of surrounding solvent and thereby correctly represents the electronic structure of the hydrated species, which is qualitatively different from that of the gas phase anion. This technique was used to study the structure and dynamics of the solvated OH^- ion, the structure and dynamics of the solvent water, and H-exchange among these species. Analysis of OH^- diffusion shows that the Grotthuss shuttling mechanism plays a crucial role and approximately doubles the diffusion rate in comparison with the system where this shuttling was artificially quenched.

Ufimtsev, I. S.; Kalinichev, A. G.; Martinez, T. J.; Kirkpatrick, R.

2006-12-01

43

Resonating-valence-bond state: Comments on the antiferromagnetic ordering of the two-dimensional Heisenberg model  

NASA Astrophysics Data System (ADS)

We consider a resonating-valence-bond state as a trial wave function for the ground state of the antiferromagnetic Heisenberg model on the square lattice. The energy and the staggered spin-spin correlation functions are calculated on a small lattice and are compared with the results of the exact diagonalization of Oitmaa and Betts. The trial energy is only about 4.7% different from the exact ground-state energy on a 4×4 lattice. The importance of the singlet pairs between the next-nearest antiferromagnetic sites is inferred. An argument against the previous interpretation of the numerical data as being evidence of long-range order is presented.

Kohmoto, Mahito

1988-03-01

44

Tuning of valence States, bonding types, hierarchical structures, and physical properties in copper/halide/isonicotinate system.  

PubMed

Seven cupric halide coordination polymers, namely [Cu5(OH)3Br3(ina)4] (1), [Cu5(OH)3Cl3(ina)4] (2), [Cu2(OH)Cl(ina)2] (3), [Cu3(OH)2Cl2(ina)2]·2H2O (4), [Cu3(OH)2Br2(ina)2]·2H2O (5), [Cu2Cl2(ina)2(H2O)2] (6), [Cu2Cl(ina)2(gca)(H2O)] (7), cupric complex templated cuprous halide [Cu(II)(Me-ina)2(H2O)][Cu(I)5Br7] (8), and organic templated cuprous halide Me2-ina[Cu2Br3] (9) (Hina = isonicotinic acid), were prepared from the starting materials of cupric halide and Hina via fine-tuning solvothermal reactions. According to valence states of copper, 1-7 are copper(II) complexes, 8 is a mixed-valent Cu(I,II) complex, while 9 is a Cu(I) compound. According to bonding types of halides, nine complexes can be classified as three types: complexes 1-3 include only normal X-Cu bond (X = halide); complexes 4-7 include normal X-Cu bond and X···Cu weak bond; complexes 8 and 9 include normal X-Cu bond and X···H-C halogen hydrogen bonds. Complexes 1 and 2 are isomorphic three-dimensional (3D) pcu topological metal organic frameworks (MOFs) with butterfly-like Cu4(?3-OH)2X2 and steplike Cu6(?3-OH)4 cores as nodes, showing strong ferromagnetic couplings. Complex 3 also is a pcu topological MOF with only butterfly-like Cu4(?3-OH)2Cl2 clusters as nodes, presenting spin canting antiferromagnetic behavior. Isostructural 4 and 5 are Cu3(OH)2 clusters based two-dimensional (2D) (4,4) layers, which are extended into 3D eight-connected networks via weak Cu···X bonds, showing ferromagnetic coupling. Antiferromagnetic 6 is a simple one-dimensional coordination polymer, which is extended via weak Cu···Cl bonds into 3D (3,4)-connected networks. Paramagnetic 7 is a ladderlike polymer, which is extended into 2D (3,4)-connected layer via weak Cu···Cl bonds. The syntheses of polymeric cupric complexes 1-7 mainly result from differences in reactant ratio and pH value. Utilization of reducing methanol generated novel cubane-containing [Cu5Br7](2-) chain templated by paddlewheel-like [Cu(II)(Me-ina)2](2+) 8 and face-shared dimer-containing [Cu2Br3](-) chain templated by N-methylated and O-esterificated Me2-ina 9. Complex 9 exhibits a strong red emission and a weaker green emission upon excitation. PMID:24712729

Liu, Min-Min; Hou, Juan-Juan; Qi, Zhi-Kai; Duan, Li Na; Ji, Wen-Juan; Han, Cai-Yun; Zhang, Xian-Ming

2014-04-21

45

Valence-bond-solid phases and quantum phase transitions in two-dimensional spin models with four-site interactions  

NASA Astrophysics Data System (ADS)

We discuss zero-temperature phase transititions from an antiferromagnetic ground state into a valence-bond-solid (VBS) in two different square-lattice quantum spin models. In one limit these models reduce to the standard S = 1/2 XY and Heisenberg models, respectively, which have long-range antiferromagnetic order at T = 0. Introducing particular types of four-spin interactions, amenable to quantum Monte Carlo (QMC) simulation without negative-sign problems, drives phase transitions into VBS states with broken Z4 symmetry. It has recently been argued that continuous quantum phase transitions of this nature represent a new class of deconfined quantum-critical points [Senthil et al., Science 303, 1490 (2004)], which are not captured within the standard Ginzburg-Landau framework of phase transitions. Here we discuss a QMC study aimed at accurately characterizing the transition in the XY model. We find some evidence that the transition is actually weakly first-order, but other scenarios, such as a continuous transition violating hyperscaling, also cannot be completely ruled out. For the Heisenberg model with four-spin interactions we have confirmed that a VBS state exists. Preliminary finite-size scaling results show consistency with a continuous transition into the Néel state, with dynamic exponent z = 1. This model is thus a candidate for deconfined quantum criticality.

Sandvik, A. W.; Melko, R. G.; Scalapino, D. J.

2006-02-01

46

Getting more out of X{sub 2}T{sub 2}O{sub 7} compounds with thortveitite structure: The bond-valence model  

SciTech Connect

C-M{sub 2}Si{sub 2}O{sub 7} (M=RE and In) and crystals of composition X{sub 2}T{sub 2}O{sub 7} (T=P, As, Ge) with ionic radius of X less than 0.97 A (X=Ni, Cd, Mg, Zn, Cu, Ca) are isostructural with the natural-occurring mineral thortveitite. In those compounds, the T-O bridging distance values vary considerably and there is no explanation to this fact in the literature. This paper will bring their structural characteristics out by the bond-valence model. It has been concluded that T-O bridging distance and mean T-O distance are linearly correlated to the total atomic valence of the bridging oxygen and the T atom (T=Si, P, As, Ge), respectively, and they are a function of the principal quantum number (n) in the valence shell of the atom T. Finally, we have applied successfully the model for the prediction of Ge-O distances of (In,A){sub 2}Ge{sub 2}O{sub 7} (A=Fe,Y,Gd) compounds. - Graphical abstract: T-O bridging distance and mean T-O distance are linearly correlated to the total atomic valence of the bridging oxygen and the silicon, respectively, and they are a function of the principal quantum number (n) of the valence shell of the atom T.

Alba, M.D. [Instituto de Ciencia de Materiales de Sevilla-Dpto. Quimica Inorganica, CSIC-Universidad de Sevilla, Avda. Americo Vespucio s/n, 41092 Sevilla (Spain)], E-mail: alba@icmse.csic.es; Becerro, A.I.; Chain, P.; Escudero, A.; Gonzalez-Carrascosa, T. [Instituto de Ciencia de Materiales de Sevilla-Dpto. Quimica Inorganica, CSIC-Universidad de Sevilla, Avda. Americo Vespucio s/n, 41092 Sevilla (Spain)

2008-02-15

47

JOURNAL DE PHYSIQUE Colloque C4, supplment au n" 4, Tome 40, avril 1979, page C4-228 BOA valence bonding with f-character in highly coordinated actinides  

E-print Network

JOURNAL DE PHYSIQUE Colloque C4, supplément au n" 4, Tome 40, avril 1979, page C4-228 BOA valence Orbital Approximation (BOA) valence bonding hybridized orbitals are characte- rized by two lobes of high and the CrUS3 structures, respectively [3, 4]. The BOA method involves using the Cf and Gf orbitals

Paris-Sud XI, Université de

48

Change of the cerium valence with temperature - Structure and chemical bonding of HT-CeRhGe  

NASA Astrophysics Data System (ADS)

Polycrystalline CeRhGe was prepared via arc-melting of the elements. Its TiNiSi-related structures (space groups Pnma) were studied by powder diffraction using synchrotron radiation over the temperature range of 315-770 K. CeRhGe shows a first-order structural phase transition at 520 K upon heating. Ab initio elelectronic structure calculations give evidence for the depletion of the cerium 4f band in HT-CeRhGe and in consequence a redistribution of the electron density from the cerium to the rhodium atoms. Purely trivalent cerium atoms in the low-temperature modification (LT) change to intermediate-valent cerium in the high-temperature modification (HT). The integrated crystal orbital Hamilton populations show an enhancement of the Ce-Rh bonding in HT-CeRhGe. The three-dimensional [RhGe] polyanionic network shows drastic puckering of the [Rh3Ge3] hexagons in LT-CeRhGe and a flattening in HT-CeRhGe. The cerium valence change is accompanied by a drastic jump in the lattice parameters: a = 7.42249(8), b = 4.46699(5) and c = 7.1276(1) Å at 315 K vs. a = 7.24579(6), b = 4.47506(4) and c = 7.43579(6) Å at 570 K. Large shifts occur for the x parameter of the rhodium and the z parameter of the cerium atomic positions (Wyckoff sites 4c (x 1/4 z)).

Svitlyk, Volodymyr; Hermes, Wilfried; Chevalier, Bernard; Matar, Samir F.; Gaudin, Etienne; Voßwinkel, Daniel; Chernyshov, Dmitry; Hoffmann, Rolf-Dieter; Pöttgen, Rainer

2013-07-01

49

Bond-valence analysis of the structure of (Ba{sub 0.875}Sr{sub 0.125})RuO{sub 3}  

SciTech Connect

The structure of TRuO{sub 3} (T = Ba{sub 0.875}Sr{sub 0.125}) has been analyzed using the bond valence procedures developed by Brown [e.g., Acta Crystallogr. Sect. B48, 553 (1992)] and O`Keeffe [Structure and Bonding 71, 161 (1989)]. The experimental results, which show overbonded and underbonded T and Ru cations, respectively, are explained by the fact that the theoretical T-O and Ru-O distances that completely satisfy the valence requirements of the atoms are incommensurate under the constraints imposed by the site symmetries of the special positions occupied by the atoms. Starting from a model derived from sphere packing geometry and the theoretical bond lengths, it is possible to evaluate the lattice parameters and the atomic shifts that minimize the strains introduced into the structure by the incommensurability of the theoretical Ru-O and T-O distances, and to arrive at a model quite close to the experimental results without making use of any prior knowledge of the structure. According to this analysis, therefore, the observed structure is interpreted as resulting from a compromise between the different bond distance requirements of the Ru and T cations.

Santoro, A.; Natali Sora, I.; Huang, Q. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). NIST Center for Neutron Research] [National Inst. of Standards and Technology, Gaithersburg, MD (United States). NIST Center for Neutron Research

1999-02-15

50

Chemical bond characterization of a mixed-valence tri-cobalt complex, Co3(?-admtrz)4(?-OH)2(CN)6·2H2O.  

PubMed

Charge density study of a mixed-valence tri-cobalt compound, Co3(?-admtrz)4(?-OH)2(CN)6·2H2O (1) (admtrz = 3,5-dimethyl-4-amino-1,2,4-triazole), is investigated based on high resolution X-ray diffraction data and density functional theory (DFT) calculations. The molecular structure of this compound contains three cobalt atoms in a linear fashion, where two terminal ones are Co(III) at a low-spin (LS) state and a central one is Co(II) at a high-spin (HS) state with a total spin quantum number, S(total), of 3/2. It is centrosymmetric with the center of inversion located at the central Co atom (Co2). The Co2 ion is linked with each terminal cobalt (Co1) ion through two ?-admtrz ligands and a ?-OH ligand in a CoN4O2 coordination, where the Co1 is bonded additionally to three CN ligands with CoN2OC3 coordination. The combined experimental and theoretical charge density study identifies the different characters of two types of cobalt ions; more pronounced charge concentration and depletion features in the valence shell charge concentration (VSCC) are found in the Co(III) ion than in the Co(II) ion, and d-orbital populations also show the difference. According to topological properties associated with the bond critical point (BCP), the Co1-C(N) bond is the strongest among all the Co-ligand bonds in this compound; the Co-O is stronger than Co-N bond. Again Co1-O is stronger than Co2-O, so as the Co1-N being stronger than Co2-N bond. The electronic configuration of each type of Co atom is further characterized through magnetic measurement, Co-specific X-ray absorption near edge spectroscopy (XANES), and X-ray emission spectra (XES). PMID:24044777

Wu, Lai-Chin; Weng, Tsu-Chien; Hsu, I-Jui; Liu, Yi-Hung; Lee, Gene-Hsiang; Lee, Jyh-Fu; Wang, Yu

2013-10-01

51

The McClure and Weiss models of Fe-O2 bonding for oxyhemes, and the HbO2 + NO reaction.  

PubMed

For the Fe-O2(S = 0) linkages of oxyhemes, valence bond (VB) structures are re-presented for the McClure [Fe(II)(S = 1) + O2(S = 1)], Pauling-Coryell [Fe(II)(S = 0) + O2*(S = 0)], and Weiss [Fe(III)(S = ½) + O2 (-)(S = ½)] models of bonding. The VB structures for the McClure and Weiss models are of the increased-valence type, with more electrons participating in bonding than occur in their component Lewis structures. The Fe-O bond number and O-O bond order for the McClure structure are correlated with measured Fe-O and O-O bond lengths for oxymyoglobin. Back-bonding from O2(-) to Fe(III) of the Weiss structure gives a restricted form of the McClure structure. The McClure and Weiss increased-valence structures are used to provide VB formulations of mechanisms for the oxyhemoglobin + NO reaction. The products of these two formulations are Hb(+) and NO3(-) (where Hb is hemoglobin) and Hb(+) and OONO(-), respectively. Because Hb(+) and NO3(-) are the observed products, they provide an experimental procedure for distinguishing the McClure and Weiss models. It is also shown that the same type of agreement between McClure-type theory and experiment occurs for oxycoboglobin + NO, cytochrome P450 monooxygenases, and related hydrogen atom transfer reactions. In the appendices, the results of density functional theory and multireference molecular orbital calculations for oxyhemes are related to one formulation of the increased-valence wavefunction for the McClure model, and theory is presented for the calculation of approximate weights for the Lewis structures that are components of the McClure increased-valence structure. PMID:24317540

Harcourt, Richard D

2014-01-01

52

Electronic structure and chemical bonding of {alpha}- and {beta}-CeIr{sub 2}Si{sub 2} intermediate valence compounds  

SciTech Connect

The dimorphism of the intermediate valence ternary cerium silicide CeIr{sub 2}Si{sub 2} in the ThCr{sub 2}Si{sub 2} ({alpha}) and CaBe{sub 2}Ge{sub 2} ({beta}) modifications is addressed in the framework of the density functional theory. The geometry optimization is in good agreement with the experiment and the subsequent establishment of the energy-volume equation of state (EOS) indicates a stabilization of the {beta}-type relative to the {alpha}-type concomitant with the trend of the cerium valence, changing to tetravalent in {beta}-CeIr{sub 2}Si{sub 2}. This is equally shown from the site projected DOS and from the large increase of the electronic contribution to the specific heat. The chemical bonding indicates the strongest bonding interactions within the Ir-Si substructure in both varieties. Stabilization of {beta}-CeIr{sub 2}Si{sub 2} with almost tetravalent cerium is in good agreement with Th{sup IV}Ir{sub 2}Si{sub 2} which exclusively crystallizes in the CaBe{sub 2}Ge{sub 2} type. The EOS behavior of different RIr{sub 2}Si{sub 2} (R=Th, Ce, La) is comparatively discussed. - Graphical abstract: The crystal structures of {alpha}- and {beta}-CeIr{sub 2}Si{sub 2}. Relevant interatomic distances (A), the three-dimensional [Ir{sub 2}Si{sub 2}] networks and the crystallographically independent iridium and silicon sites are indicated. Highlights: Black-Right-Pointing-Pointer Energy stabilization of (HT) {beta}-CeIr{sub 2}Si{sub 2} versus (LT) {alpha}-CeIr{sub 2}Si{sub 2} from DFT methods. Black-Right-Pointing-Pointer Concomitant with the change of Ce valence to tetravalent (HT)-enhanced specific heat. Black-Right-Pointing-Pointer Equations of states for La, Ce and Th members with CeIr{sub 2}Si{sub 2} resembling tetravalent-Th. Black-Right-Pointing-Pointer Chemical bonding shows changes on the {l_brace}Ir{sub 2}Si{sub 2}{r_brace} intralayer and Ce{sup IV}-Ir bonds.

Matar, Samir F., E-mail: matar@icmcb-bordeaux.cnrs.fr [CNRS, Universite de Bordeaux, ICMCB, 87 Avenue du Docteur Albert Schweitzer, 33600 Pessac (France); Poettgen, Rainer, E-mail: pottgen@uni-muenster.de [Institut fuer Anorganische Universitaet Muenster, Corrensstrasse 30, D-48149 Muenster (Germany); Chevalier, Bernard, E-mail: chevalie@icmcb-bordeaux.cnrs.fr [CNRS, Universite de Bordeaux, ICMCB, 87 Avenue du Docteur Albert Schweitzer, 33600 Pessac (France)

2012-02-15

53

Crystal structure of phospholipase PA2-Vb, a protease-activated receptor agonist from the Trimeresurus stejnegeri snake venom.  

PubMed

Phospholipase A2 (PLA2) is an important component in snake venoms. Here, an acidic PLA2, designated PA2-Vb was isolated from the Trimeresurus stejnegeri snake venom. PA2-Vb acts on a protease-activated receptor (PAR-1) to evoke Ca(2+) release through the inositol 1,4,5-trisphosphate receptor (IP3R) and induces mouse aorta contraction. PAR-1, phospholipase C and IP3R inhibitors suppressed PA2-Vb-induced aorta contraction. The crystal structure reveals that PA2-Vb has the typical fold of most snake venom PLA2. Several PEG molecules bond to a positively charged pocket. The finding offers a novel pharmacological basis of the structure for investigating the PAR-1 receptor and suggests potential applications for PA2-Vb in the vascular system. PMID:25447533

Zeng, Fuxing; Zhang, Wenjuan; Xue, Nairui; Teng, Maikun; Li, Xu; Shen, Bing

2014-12-20

54

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

PubMed

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

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

2012-03-30

55

Atomic Structure and Valence: Level II, Unit 10, Lesson 1; Chemical Bonding: Lesson 2; The Table of Elements: Lesson 3; Electrolysis: Lesson 4. Advanced General Education Program. A High School Self-Study Program.  

ERIC Educational Resources Information Center

This self-study program for high-school level contains lessons on: Atomic Structure and Valence, Chemical Bonding, The Table of Elements, and Electrolysis. Each of the lessons concludes with a Mastery Test to be completed by the student. (DB)

Manpower Administration (DOL), Washington, DC. Job Corps.

56

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

SciTech Connect

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

Ponou, Simeon [Centre for Analysis and Synthesis, Lund University; Lidin, Sven [Centre for Analysis and Synthesis, Lund University; Zhang, Yuemei [Ames Laboratory; Miller, Gordon J. [Ames Laboratory

2014-04-18

57

Valence state driven site preference in the quaternary compound Ca5MgAgGe5: an electron-deficient phase with optimized bonding.  

PubMed

The quaternary phase Ca5Mg0.95Ag1.05(1)Ge5 (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma-Wyckoff sequence c(12) with a = 23.1481(4) Å, b = 4.4736(1) Å, c = 11.0128(2) Å, V = 1140.43(4) Å(3), Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R(2+n)T2X(2+n), previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm-Wyckoff sequence f(5)c(2). The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO electronic structure calculations indicate electronic stabilization and overall bonding optimization in the polyanionic network. Other stability factors beyond the Zintl concept that may account for the electronic stabilization are discussed. PMID:24745932

Ponou, Siméon; Lidin, Sven; Zhang, Yuemei; Miller, Gordon J

2014-05-01

58

Mercury Catcher Status V.B. Graves  

E-print Network

Mercury Catcher Status V.B. Graves Hg Jet Design Meeting Princeton University Nov 15, 2004 #12;OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Hg Jet Design Meeting ­ 15 Nov 2004 Hg Catcher Design · Purposes - Receive 20m/s Hg jet after beam interaction - Redirect flow out of primary tube

McDonald, Kirk

59

Mercury Nozzle Status V.B. Graves  

E-print Network

Mercury Nozzle Status V.B. Graves Hg Jet Design Meeting Princeton University Nov 15, 2004 #12;OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Hg Jet Design Meeting ­ 15 Nov 2004 Nozzle. DEPARTMENT OF ENERGY Hg Jet Design Meeting ­ 15 Nov 2004 Flow Issues · High flow in small diameter thin

McDonald, Kirk

60

Unprecedented structural variations in trinuclear mixed valence Co(ii/iii) complexes: theoretical studies, pnicogen bonding interactions and catecholase-like activities.  

PubMed

Three new mixed valence trinuclear Co(ii/iii) compounds cis-[Co3L2(MeOH)2(N3)2(?1,1-N3)2] (), trans-[Co3L2(H2O)2(N3)2(?1,1-N3)2]·(H2O)2 () and [Co3L(R)2(N3)3(?1,3-N3)] () have been synthesized by reacting a di-Schiff base ligand () or its reduced form [] (where = N,N'-bis(salicylidene)-1,3-propanediamine and = N,N'-bis(2-hydroxybenzyl)-1,3-propanediamine) with cobalt perchlorate hexahydrate and sodium azide. All three products have been characterized by IR, UV-Vis and EPR spectroscopies, ESI-MS, elemental, powder and single crystal X-ray diffraction analyses. Complex is an angular trinuclear species in which two terminal octahedral Co(iii)N2O4 centers coordinate to the central octahedral cobalt(ii) ion through ?2-phenoxido oxygen and ?1,1-azido nitrogen atoms along with two mutually cis-oxygen atoms of methanol molecules. On the other hand, in linear trinuclear complex , in addition to the ?2-phenoxido and ?1,1-azido bridges with terminal octahedral Co(iii) centres, the central Co(ii) is bonded with two mutually trans-oxygen atoms of water molecules. Thus the cis-trans configuration of the central Co(ii) is solvent dependent. In complex , the two terminal octahedral Co(iii)N2O4 centers coordinate to the central penta-coordinated Co(ii) ion through double phenoxido bridges along with the nitrogen atom of a terminal azido ligand. In addition, the two terminal Co(iii) are connected through a ?1,3-azido bridge that participates in pnicogen bonding interactions (intermolecular N-N interaction) as an acceptor. Both the cis and trans isomeric forms of and have been optimized using density functional theory (DFT) calculations and it is found that the cis configuration is energetically more favorable than the trans one. However, the trans configuration of is stabilized by the hydrogen bonding network involving a water dimer. The pnicogen bonding interactions have been demonstrated using MEP surfaces and CSD search which support the counter intuitive electron acceptor ability of the ?1,3-azido ligand. Complexes exhibit catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone. Kinetic data analyses of this oxidation reaction in acetonitrile reveal that the catecholase-like activity follows the order: (kcat = 142 h(-1)) > (kcat = 99 h(-1)) > (kcat = 85 h(-1)). Mechanistic investigations of the catalytic behaviors by X-band EPR spectroscopy and estimation of hydrogen peroxide formation indicate that the oxidation reaction proceeds through the reduction of Co(iii) to Co(ii). PMID:25611163

Hazari, Alokesh; Kanta Das, Lakshmi; Kadam, Ramakant M; Bauzá, Antonio; Frontera, Antonio; Ghosh, Ashutosh

2015-02-10

61

Bonding  

NSDL National Science Digital Library

Bonding Purpose: To review the 3 Types of Bonds and the 4 Intermolecular Forces. Assignment: Answer the following questions on a separate piece of paper: 1) List the 3 types of bonding, give descriptions and one example of each 2) List the 4 intermolecular forces and draw examples of each. Be ...

Cutting, Mrs.

2008-03-08

62

Effect of the valence electron concentration on the bulk modulus and chemical bonding in Ta{sub 2}AC and Zr{sub 2}AC (A=Al, Si, and P)  

SciTech Connect

We have studied the effect of the valence electron concentration, on the bulk modulus and the chemical bonding in Ta{sub 2}AC and Zr{sub 2}AC (A=Al, Si, and P) by means of ab initio calculations. Our equilibrium volume and the hexagonal ratio (c/a) agree well (within 2.7% and 1.2%, respectively) with previously published experimental data for Ta{sub 2}AlC. The bulk moduli of both Ta{sub 2}AC and Zr{sub 2}AC increase as Al is substituted with Si and P by 13.1% and 20.1%, respectively. This can be understood since the substitution is associated with an increased valence electron concentration, resulting in band filling and an extensive increase in cohesion.

Schneider, Jochen M.; Music, Denis; Sun Zhimei [Materials Chemistry, RWTH Aachen, Kopernikusstr.16, D-52074 Aachen (Germany)

2005-03-15

63

Direct infrared imaging of VB 8  

NASA Astrophysics Data System (ADS)

Near-infrared images of VB 8 taken at K (2.2 microns) and L-prime (3.75 microns) during a period of good seeing at the IRTF show no evidence of the brown dwarf companion reported by McCarthy et al. (1985). Any companion 1.0 arcsec away from the primary must be at least 4 mag fainter than the primary at K and 3 mag fainter at L-prime in order to escape detection. A faint nebula centered on the star with scattering properties similar to a nebula detected near another main-sequence M star, Lalande 21185 (reported by McCarthy in 1986), may account for the extended emission detected by speckle observations.

Skrutskie, M. F.; Forrest, W. J.; Shure, M. A.

1987-01-01

64

Levels of Valence  

PubMed Central

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 (un)pleasantness, goal obstructiveness/conduciveness, low or high power, self-(in)congruence, 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. PMID:23717292

Shuman, Vera; Sander, David; Scherer, Klaus R.

2013-01-01

65

Conformation-Determined Through-Bond versus Through-Space Electronic Communication in Mixed-Valence Systems with a Cross-Conjugated Urea Bridge.  

PubMed

Bis-triarylamine 2 and cyclometalated diruthenium 6(PF6 )2 with a linear trans,trans-urea bridge have been prepared, together with the bis-triarylamine 3 and cyclometalated diruthenium 8(PF6 )2 with a folded cis,cis-N,N-dimethylurea bridge. The linear or folded conformations of these molecules are supported by single-crystal X-ray structures of 2, 3, and other related compounds. These compounds display two consecutive anodic redox waves (N(.) (+/0) or Ru(III/II) processes) with a potential separation of 110-170?mV. This suggests that an efficient electronic coupling is present between two redox termini through the cross-conjugated urea bridge. The degree of electronic coupling has been investigated by using spectroelectrochemical measurements. Distinct intervalence charge-transfer (IVCT) transitions have been observed for mixed-valent (MV) compounds with a linear conformation. The IVCT transitions can also be identified for the folded MV compounds, albeit with a much weaker intensity. DFT results support that the electronic communication occurs by a through-bond and through-space pathway for the linear and folded compounds, respectively. The IVCT transitions of the MV compounds have been reproduced by TDDFT calculations. For the purpose of comparison, a bistriarylamine and a diruthenium complex with an imidazolidin-2-one bridge and a urea-containing mono-triarylamine and monoruthenium complex have been synthesized and studied. PMID:25421648

Gong, Zhong-Liang; Zhong, Yu-Wu; Yao, Jiannian

2014-11-24

66

Draft Genome Sequence of Tolypothrix boutellei Strain VB521301  

PubMed Central

We report here the draft genome sequence of the filamentous nitrogen-fixing cyanobacterium Tolypothrix boutellei strain VB521301. The organism is lipid rich and hydrophobic and produces polyunsaturated fatty acids which can be harnessed for industrial purpose. The draft genome sequence assembled into 11,572,263 bp with 70 scaffolds and 7,777 protein coding genes.

Chandrababunaidu, Mathu Malar; Singh, Deeksha; Sen, Diya; Bhan, Sushma; Das, Subhadeep; Gupta, Akash

2015-01-01

67

Chem 350 Jasperse Ch. 1 Normal Bonding; Drawing Lewis Structures 1 Normal Bonds (Sections 1.2-1.5)  

E-print Network

Chem 350 Jasperse Ch. 1 Normal Bonding; Drawing Lewis Structures 1 Normal Bonds (Sections 1.2-1.5) Summary of Normal, Ideal Bonding (No Formal Charge) Valence Electrons Valence Bonds Lone Pairs C 4 4 0 N 5: (Sections 1.4-5) 1. Try to provide normal bonding for C, N, O atoms if possible. (Works > 95% of time) 2

Jasperse, Craig P.

68

Research on communication between computer and PLC based on VB  

Microsoft Academic Search

This paper mainly introduces the communication between computer and S7–200PLC of Siemens, in which host computer (PC) adopts MSComm control in VB6.0, a visual programming language, to implement the data communication between console computer (S7–200 PLC) and computer, based on free port communication protocol. Communication protocol format is user-defined in this paper, so huge data communication in real time can

Hui Fang; Wei Tang

2012-01-01

69

Valence, Covalence, Hypervalence, Oxidation State, and Coordination Number  

ERIC Educational Resources Information Center

Valence as a numerical measure of an atom's combining power, expressed by the number of bonds it forms in a molecular formulation of the compound in question, was unable to cope with coordination compounds. The covalence of an atom is the nearest model equivalent, but is subject to ambiguity since it often depends on which bonding model is being…

Smith, Derek W.

2005-01-01

70

Multi-gate vibrating-body field effect transistor (VB-FETs)  

Microsoft Academic Search

This paper reports on the design, fabrication and detailed characteristics of multi-gate vibrating-body field effect transistors (VB-FETs). Double-gate and four-gate VB-FETs with resonance frequencies of 2 MHz and 71 MHz, respectively, are successfully demonstrated. The VB-FETs exhibit built-in amplification (more than +30 dB improvement of signal detection compared with capacitive detection), low motional resistances (in the orders kOhms down to

Daniel Grogg; Marco Mazza; Dimitrios Tsamados; Adrian Mihai Ionescu

2008-01-01

71

THE PROPOSED GIANT PLANET ORBITING VB 10 DOES NOT EXIST  

SciTech Connect

We present high-precision relative radial velocities of the very low mass star VB 10 that were obtained over a time span of 0.61 years as part of an ongoing search for planets around stars at the end of the main sequence. The radial velocities were measured from high-resolution near-infrared spectra obtained using the CRIRES instrument on the Very Large Telescope with an ammonia gas cell. The typical internal precision of the measurements is 10 m s{sup -1}. These data do not exhibit significant variability and are essentially constant at a level consistent with the measurement uncertainties. Therefore, we do not detect the radial velocity variations of VB 10 expected due to the presence of an orbiting giant planet similar to that recently proposed by Pravdo and Shaklan based on apparent astrometric perturbations. In addition, we do not confirm the {approx}1 km s{sup -1} radial velocity variability of the star tentatively detected by Zapatero Osorio and colleagues with lower precision measurements. Our measurements rule out planets with M {sub p} > 3 M {sub Jup} and the orbital period and inclination suggested by Pravdo and Shaklan at better than 5{sigma} confidence. We conclude that the planet detection claimed by Pravdo and Shaklan is spurious on the basis of this result. Although the outcome of this work is a non-detection, it illustrates the potential of using ammonia cell radial velocities to detect planets around very low mass stars.

Bean, Jacob L.; Seifahrt, Andreas; Reiners, Ansgar; Dreizler, Stefan [Institut fuer Astrophysik, Georg-August-Universitaet, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Hartman, Henrik; Nilsson, Hampus [Lund Observatory, Lund University, P.O. Box 43, 22100 Lund (Sweden); Henry, Todd J. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302 (United States); Wiedemann, Guenter [Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg (Germany)], E-mail: bean@astro.physik.uni-goettingen.de

2010-03-01

72

Direct determination of the band offset in atomic layer deposited ZnO/hydrogenated amorphous silicon heterojunctions from X-ray photoelectron spectroscopy valence band spectra  

SciTech Connect

The chemical composition and band alignment at the heterointerface between atomic layer deposition-grown zinc oxide (ZnO) and hydrogenated amorphous silicon (a-Si:H) is investigated using monochromatized X-ray photoelectron spectroscopy. A new approach for obtaining the valence band offset ?E{sub V} is developed, which consists in fitting the valence band (VB) spectrum obtained for a-Si:H with a thin ZnO overlayer as the sum of experimentally obtained VB spectra of a bulk a-Si:H film and a thick ZnO film. This approach allows obtaining ?E{sub V}?=?2.71?±?0.15?eV with a minimum of assumptions, and also yields information on the change in band bending of both substrate and ZnO film. The band offset results are compared to values obtained using the usual approach of comparing valence band edge-to-core level energy differences, ?E{sub B,CL} ???E{sub B,VB}. Furthermore, a theoretical value for the VB offset is calculated from the concept of charge neutrality level line-up, using literature data for the charge neutrality levels and the experimentally determined ZnO/a-Si:H interface dipole. The thus obtained value of ?E{sub V}{sup CNL}?=?2.65?±?0.3?eV agrees well with the experimental ?E{sub V}.

Korte, L., E-mail: korte@helmholtz-berlin.de; Rößler, R.; Pettenkofer, C. [Helmholtz-Zentrum Berlin, Institute for Silicon Photovoltaics, Kekuléstrasse 5, 12489 Berlin (Germany)

2014-05-28

73

En jämförande studie av Visual C++, C# och VB.NET; A Comparative Study of Visual C++, C# and VB.NET.  

E-print Network

?? Programmeringsspråken Visual C++, C# och VB.NET (Visual Basic.NET) jämförs, med tyngdpunkt på en praktisk jämförelse av fyra exempelapplikationer. Exempelapplikationen WordCount visar att Visual C++… (more)

Krisell, Magnus

2005-01-01

74

Micro-valences: perceiving affective valence in everyday objects.  

PubMed

Perceiving the affective valence of objects influences how we think about and react to the world around us. Conversely, the speed and quality with which we visually recognize objects in a visual scene can vary dramatically depending on that scene's affective content. Although typical visual scenes contain mostly "everyday" objects, the affect perception in visual objects has been studied using somewhat atypical stimuli with strong affective valences (e.g., guns or roses). Here we explore whether affective valence must be strong or overt to exert an effect on our visual perception. We conclude that everyday objects carry subtle affective valences - "micro-valences" - which are intrinsic to their perceptual representation. PMID:22529828

Lebrecht, Sophie; Bar, Moshe; Barrett, Lisa Feldman; Tarr, Michael J

2012-01-01

75

Valence photoelectron spectroscopy of Gd silicides  

SciTech Connect

Gd{sub 3}Si{sub 5}, GdSi, and Gd{sub 5}Si{sub 3} were investigated with photoemission spectroscopy in the photon-energy range 40.8--149 eV by exploiting the energy dependence of the photoemission cross sections and the valence resonance at the crossing of the Gd 4{ital d}-4{ital f} threshold. The modification of the spectra versus photon energy, along with their stoichiometry dependence, show the relevance of covalent mixed Gd 5{ital d}--Si 3{ital sp} states in the formation of the chemical bond. In the region close to the Fermi level an increase of the {ital d} contribution is observed. These points are discussed in connection with the existing models of the silicide bond.

Braicovich, L. (Istituto di Fisica, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano, Italy (IT)); Puppin, E.; Lindau, I. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94305 (USA)); Iandelli, A.; Olcese, G.L.; Palenzona, A. (Istituto di Chimica Fisica, Universita di Genova, Corso Europa, Palazzo delle Scienze, 16132 Genova, (Italy))

1990-02-15

76

Real-Time Evolution of the Valence Electronic Structure in a Dissociating Molecule  

SciTech Connect

Time-resolved valence band photoelectron spectroscopy with a temporal resolution of 135 fs is used to map the entire occupied valence electronic structure of photoexcited gas-phase Br{sub 2} molecules during dissociation. The observed shifting and mixing of valence energy levels defines a transition period where the system appears to be intermediate between atoms and molecules. The surprisingly short bond breaking or dissociation time is determined by monitoring in real time how the photoelectron multiplet structure of the free atom arises from the valence states of the photoexcited molecule.

Wernet, Ph.; Godehusen, K.; Gaudin, J.; Schwarzkopf, O.; Eberhardt, W. [Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany); Odelius, M. [FYSIKUM, Stockholm University, AlbaNova, S-106 91 Stockholm (Sweden)

2009-07-03

77

Bonding with parallel spins: high-spin clusters of monovalent metal atoms.  

PubMed

Bonding is a glue of chemical matter and is also a useful concept for designing new molecules. Despite the fact that electron pairing remains the bonding mechanism in the great majority of molecules, in the past few decades scientists have had a growing interest in discovering novel bonding motifs. As this Account shows, monovalent metallic atoms having exclusively parallel spins, such as (11)Li10, (11)Au10, and (11)Cu10, can nevertheless form strongly bound clusters, without having even one traditional bond due to electron pairing. These clusters, which also can be made chiral, have high magnetic moments. We refer to this type as no-pair ferromagnetic (NPFM) bonding, which characterizes the (n+1)Mn clusters, which were all predicted by theoretical computations. The small NPFM alkali clusters that have been "synthesized" to date, using cold-atom techniques, support the computational predictions. In this Account, we describe the origins of NPFM bonding using a valence bond (VB) analysis, which shows that this bonding motif arises from bound triplet electron pairs that spread over all the close neighbors of a given atom in the cluster. The bound triplet pair owes its stabilization to the resonance energy provided by the mixing of the local ionic configurations, [(3)M(??)(-)]M(+) and M(+)[(3)M(??)(-)], and the various excited covalent configurations (involving pz and dz(2) atomic orbitals) into the repulsive covalent structure (3)(M??M) with the s(1)s(1) electronic configuration. The NPFM bond of the bound triplet is described by a resonating wave function with "in-out" and "out-in" pointing hybrids. The VB model accounts for the tendency of NPFM clusters to assume polyhedral shapes with rather high symmetry. In addition, this model explains the very steep rise of the bonding energy per atom (De/n), which starts out small in the (3)M2 dimer (<1 kcal/mol) and reaches 12-19 kcal/mol for clusters with 10 atoms. The model further predicts that usage of heteroatomic clusters should increase the bonding energy of an NPFM cluster. These NPFM clusters are excited state species. We suggest here stabilizing these states and making them accessible, for example, by using magnetic fields, or a combination of magnetic and electric fields. The advent of NPFM clusters offers new horizons in chemistry and enriches the scope of chemical bonding. These prospects form a strong incentive to investigate the origins of the bound triplet pairs and further chart the territory of NPFM clusters, for example, in clusters of Be, Mg, or Zn, possibly in clusters of their monosubstituted species, and the group III metalloids, such as B, Al, as well as in transition metals such as Sc. PMID:23941238

Danovich, David; Shaik, Sason

2014-02-18

78

Reactive Force Fields via Explicit Valency  

NASA Astrophysics Data System (ADS)

Computational simulations are invaluable in elucidating the dynamics of biological macromolecules. Unfortunately, reactions present a fundamental challenge. Calculations based on quantum mechanics can predict bond formation and rupture; however they suffer from severe length- and time-limitations. At the other extreme, classical approaches provide orders of magnitude faster simulations; however they regard chemical bonds as immutable entities. A few exceptions exist, but these are not always trivial to adopt for routine use. We bridge this gap by providing a novel, pseudo-classical approach, based on explicit valency. We unpack molecules into valence electron pairs and atomic cores. Particles bear ionic charges and interact via pairwise-only potentials. The potentials are informed of quantum effects in the short-range and obey dissociation limits in the long-range. They are trained against a small set of isolated species, including geometries and thermodynamics of small hydrides and of dimers formed by them. The resulting force field captures the essentials of reactivity, polarizability and flexibility in a simple, seamless setting. We call this model LEWIS, after the chemical theory that inspired the use of valence pairs. Following the introduction in Chapter 1, we initially focus on the properties of water. Chapter 2 considers gas phase clusters. To transition to the liquid phase, Chapter 3 describes a novel pairwise long-range compensation that performs comparably to infinite lattice summations. The approach is suited to ionic solutions in general. In Chapters 4 and 5, LEWIS is shown to correctly predict the dipolar and quadrupolar response in bulk liquid, and can accommodate proton transfers in both acid and base. Efficiency permits the study of proton defects at dilutions not accessible to experiment or quantum mechanics. Chapter 6 discusses explicit valency approaches in other hydrides, forming the basis of a reactive organic force field. Examples of simple proton transfer and more complex reactions are discussed. Chapter 7 provides a framework for variable electron spread. This addition resolves some of the inherent limitations of the former model which implicitly assumed that electron spread was not affected by the environment. A brief summary is provided in Chapter 8.

Kale, Seyit

79

Protonated alcohols are examples of complete charge-shift bonds.  

PubMed

Accurate gas-phase and solution-phase valence bond calculations reveal that protonation of the hydroxyl group of aliphatic alcohols transforms the C-O bond from a principally covalent bond to a complete charge-shift bond with principally "no-bond" character. All bonding in this charge-shift bond is due to resonance between covalent and ionic structures, which is a different bonding mechanism from that of traditional covalent bonds. Until now, charge-shift bonds have been previously identified in inorganic compounds or in exotic organic compounds. This work showcases that charge-shift bonds can occur in common organic species. PMID:25317657

Anderson, Peter; Petit, Alban; Ho, Junming; Mitoraj, Mariusz Pawel; Coote, Michelle L; Danovich, David; Shaik, Sason; Braïda, Benoît; Ess, Daniel H

2014-11-01

80

A Multidimensional Measure of Work Valences  

ERIC Educational Resources Information Center

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…

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

2012-01-01

81

Magnetic And Transport Properties Of Fe2VB Heusler Alloy: A New Report  

Microsoft Academic Search

The transport and magnetic properties of the Fe2VB Heusler alloy have been studied for the first time. The temperature dependence of electrical resistivity (upto 100 K) follows conventional ferromagnetic metallic nature. The M-H curves at 5 and 300 K exhibit ferromagnetism. However, the curie-temperature is not yet known.

M. Vasundhara; V. Srinivas; V. V. Rao; T. V. Chandrashekhar Rao

2008-01-01

82

Microhardness of Czochralski-grown single crystals of VB{sub 2}  

SciTech Connect

Single crystals of congruent melting hexagonal VB{sub 2} were grown used a triarc furnace applying the Czochralski technique. Orientation dependent microhardness measurements on a single crystal reveal quasi similar hardness in the crystallographic directions <00.1> and <10.0>, whereas the <10.1> shows slightly lower values.

Bulfon, C.; Sassik, H. [Institut fuer Experimentalphysik, Wien (Austria)] [Institut fuer Experimentalphysik, Wien (Austria); Leithe-Jasper, A.; Rogl, P. [Universitaet Wien (Austria)] [Universitaet Wien (Austria)

1997-10-01

83

JOB DESCRIPTION C#/VB Developer -ASP.NET -SQL 05,08 -HTML -AJAX  

E-print Network

JOB DESCRIPTION · C#/VB Developer - ASP.NET - SQL 05,08 - HTML - AJAX · Santa Rosa, CA Do you have#, C++, ASP.NET, HTML, CSS, AJAX, XML, Visual Studio, SQL 2005, SQL 2008 ESSENTIAL SKILLS experience using .NET 2.0 technologies such as HTML, CSS, AJAX, ASP.NET, XML · Must be looking for a senior

Ravikumar, B.

84

Valence band states and polarized optical emission from nonpolar and semipolar III–nitride quantum well optoelectronic devices  

NASA Astrophysics Data System (ADS)

Nonpolar and semipolar III–nitride quantum wells (QWs) and devices have been extensively studied due to their unique valence band (VB) structure and polarized optical emission. Unlike conventional c-plane oriented III–nitride QWs, the low crystal symmetry and unbalanced biaxial stress in nonpolar and semipolar QWs separates the topmost VBs and gives rise to polarized optical emission. Since the first experimental reports on nonpolar devices, research on this topic has progressed very rapidly and has covered nonpolar m-plane and a-plane QWs and devices as well as semipolar (11\\bar{2}2), (20\\bar{2}1), and (20\\bar{2}\\bar{1}) QWs and devices. Issues such as strain, plane inclination angle (with respect to the c-plane), indium composition, temperature, and their impact on QW VB structure and device performance have been extensively studied. In this paper we review the physical background and theoretical analysis of the VB states and polarized optical emission of nonpolar and semipolar structures and discuss their potential impacts on optoelectronic devices. Experimental results for nonpolar and semipolar light-emitting diodes and laser diodes will be covered along with additional discussions on the potential applications and challenges related to their unique physical properties.

Zhao, Yuji; Farrell, Robert M.; Wu, Yuh-Renn; Speck, James S.

2014-10-01

85

Modeling planar 3-valence meshes  

E-print Network

MODELING PLANAR 3-VALENCE MESHES A Thesis by OZGUR GONEN Submitted to the O ce of Graduate Studies of Texas A&M University in partial ful llment of the requirements for the degree of MASTER OF SCIENCE December 2007 Major Subject: Visualization... Sciences MODELING PLANAR 3-VALENCE MESHES A Thesis by OZGUR GONEN Submitted to the O ce of Graduate Studies of Texas A&M University in partial ful llment of the requirements for the degree of MASTER OF SCIENCE Approved by: Co-Chairs of Committee, Ergun...

Gonen, Ozgur

2008-10-10

86

Modeling planar 3-valence meshes  

E-print Network

MODELING PLANAR 3-VALENCE MESHES A Thesis by OZGUR GONEN Submitted to the O ce of Graduate Studies of Texas A&M University in partial ful llment of the requirements for the degree of MASTER OF SCIENCE December 2007 Major Subject: Visualization... Sciences MODELING PLANAR 3-VALENCE MESHES A Thesis by OZGUR GONEN Submitted to the O ce of Graduate Studies of Texas A&M University in partial ful llment of the requirements for the degree of MASTER OF SCIENCE Approved by: Co-Chairs of Committee, Ergun...

Gonen, Ozgur

2009-05-15

87

Symmetry and broken-symmetry in molecular orbital descriptions of unstable molecules. 3. The nature of chemical bonds of spin frustrated systems.  

PubMed

Symmetry and broken symmetry in the molecular orbital description of spin frustration systems have been investigated in relation to the resonating valence bond (RVB) theory of the spin liquid state and non-BCS superconductivity. Broken symmetry (BS) and resonating BS (RBS) molecular orbital (MO) methods have been employed to obtain resonating valence bond (RVB)-type explanations of spin frustrated systems. RBS MO solutions are expanded using the localized molecular orbitals (LMO) to elucidate a universal MO-VB description. The BS and RBS MO descriptions of triangular spin frustrated systems corresponding to transition structures for exchange-forbidden radical insertions were investigated in comparison with the RVB-type explanations of such systems. The BS and RBS calculations by the use of three different axial (SDW) solutions or three noncollinear GSO (helical SDW) solutions of a triangular hydrogen cluster were performed to obtain potential curves with and without resonance (quantum) effects. The resonating GSO (noncollinear) state responsible for short-range correlation was found to be the most stable for the system. The reliability of the approximate spin projection (AP) procedure to eliminate the high-spin component was also elucidated, comparing with the AP BS and RBS potential curves. The BS GSO (GHF) computations of several triangular systems, N(CH(2))(3), (CH(2))(3), and Mn(II)(3)O(4), were performed to obtain total energies and total spin angular momentums and effective exchange integrals (J) between local spins, which are crucial for construction of effective spin Hamiltonian models. The exact diagonalization of the Heisenberg models was also performed to depict the energy levels and magnetic susceptibility curves for triangular and kagome lattices to elucidate spin frustration effects and related quantum spin behaviors. Implications of the computational results have been discussed in relation to magnetic properties of several triangular and kagome systems synthesized recently and the superconductivity of triangular systems discovered recently. PMID:19908878

Kawakami, T; Takeda, R; Nishihara, S; Saito, T; Shoji, M; Yamada, S; Yamanaka, S; Kitagawa, Y; Okumura, M; Yamaguchi, K

2009-12-31

88

Bonding study of TiC and TiN. I. High-precision x-ray-diffraction determination of the valence-electron density distribution, Debye-Waller temperature factors, and atomic static displacements in TiC0.94 and TiN0.99  

NASA Astrophysics Data System (ADS)

Single-crystal, high-precision, high-resolution x-ray-diffraction measurements of the substoichiometric refractory compounds TiC and TiN have been performed with AgK? radiation. Severe anisotropic general extinction affects the intense low-order reflections. Inhomogeneity in the mosaic spread and domain size produces small but significant differences between reflection and antireflection for the same plane of diffraction. These effects have been modeled and refined together with a scale factor, isotropic thermal parameters, a population parameter of the nonmetal site, the amplitude of metal-atom static displacements around nonmetal vacancies, and an atomic model which includes occupancy factors of the separate orbital contributions of the valence electrons combined with ? expansion-contraction parameters. At convergence, the ``agreement indices'' (or ``reliability factors'') were R=0.0025 for TiC0.94 and R=0.0023 for TiN0.99. The refined population parameters indicate a chemical composition of TiC0.939(9) and TiN0.99(2). The mean-square amplitudes of thermal vibrations, Ti=0.002 38(2) AṦ, C=0.003 35(8) AṦ, Ti=0.002 94(1) AṦ, and N=0.003 08(12) AṦ are consistent with the respective atomic masses. 36% of the metal atoms in TiC0.94 are involved in a relaxation around the nonmetal vacancies, being displaced from their sublattice sites by 0.097(2) Å along [100]. No evidence for static displacements was found in TiN0.99. The valence-electron density distribution can be described satisfactorily in terms of deformed atoms. No buildup of charge density occurs between atomic sites. Our analysis, similar to a Mulliken partitioning, shows first that ionicity is important, with a charge transfer from the metal to the nonmetal of [2.1(4)]e in the carbide and [1.9(4)]e in the nitride, and secondly that the charge asphericity around the metal atoms is larger in the former than in the latter, while no departure from spherical symmetry is observed around the nonmetal atoms. The titanium 3d electrons can be split into a spherical shell that contains [1.27(6)]e plus an excess of [0.24(5)]e shared by two orbitals of eg symmetry in the carbide and conversely into a spherical shell that contains [0.88(11)]e plus an excess of [0.12(9)]e shared by three orbitals of t2g symmetry in the nitride. This suggests that the metal-to-metal bonding is similar in TiC and in TiN while the metal-to-nonmetal bonding is greater in TiC than in TiN.

Dunand, A.; Flack, H. D.; Yvon, K.

1985-02-01

89

Evolution of substellar 'brown' dwarfs and the evolutionary status of VB8B  

NASA Technical Reports Server (NTRS)

Detailed evolutionary calculations for stars near and below the minimum main sequence (MS) mass are presented, and the results are compared to VB8B. The standard set of stellar equations are solved, and the influence of both high and low grain opacities is assessed. All masses less than 0.08 solar are found to evolve to 0.0001 solar luminosities in a billion years or less. Both 0.08 solar mass and 0.075 solar mass stars become MS stars after five billion years, but with luminosities substantially below 0.0001 solar. The best fit to VB8B is 0.06 + or - 0.02 solar mass, but less than 0.8 solar mass. Depending upon its very precise mass, VB8B can be either a substellar brown dwarf with an age of 0.3-3 billion years, or an MS star with an age anywhere from two billion years to a Hubble time.

Stringfellow, Guy S.

1986-01-01

90

Superconductivity in the liquid-dimer valence-bond state  

SciTech Connect

Introducing an unambiguous prescription which converts singlet dimers into quasidipoles, we describe the low-energy excitations in the liquid-dimer state as fluctuations of the average dipole moment. The exchange of these fluctuations leads to a long-range interaction between holes in this state. This interaction favors the two-particle Bose condensate and destroys the order parameter of the one-particle Bose condensate even at zero temperature.

Ioffe, L.B.; Larkin, A.I. (Lev Davidovich Landau Institute for Theoretical Physics, ul. Kosygina 2, GSP-1, 117 940 Moscow, U.S.S.R. (SU))

1989-10-01

91

Three-dimensional valency mapping in ceria nanocrystals.  

PubMed

Using electron tomography combined with electron energy loss spectroscopy (EELS), we are able to map the valency of the Ce ions in CeO2-x nanocrystals in three dimensions. Our results show a clear facet-dependent reduction shell at the surface of ceria nanoparticles; {111} surface facets show a low surface reduction, whereas at {001} surface facets, the cerium ions are more likely to be reduced over a larger surface shell. Our generic tomographic technique allows a full 3D data cube to be reconstructed, containing an EELS spectrum in each voxel. This possibility enables a three-dimensional investigation of a plethora of material-specific physical properties such as valency, chemical composition, oxygen coordination, or bond lengths, triggering the synthesis of nanomaterials with improved properties. PMID:25286190

Goris, Bart; Turner, Stuart; Bals, Sara; Van Tendeloo, Gustaaf

2014-10-28

92

Pauling bond strength, bond length and electron density distribution  

SciTech Connect

A power law regression equation, = 1.46(/r)-0.19, connecting the average experimental bond lengths, , with the average accumulation of the electron density at the bond critical point, , between bonded metal M and oxygen atoms, determined at ambient conditions for oxide crystals, where r is the row number of the M atom, is similar to the regression equation R(M-O) = 1.39(?(rc)/r)-0.21 determined for three perovskite crystals for pressures as high as 80 GPa. The two equations are also comparable with those, = 1.43(/r)-0.21, determined for a large number of oxide crystals at ambient conditions and = 1.39(/r)-0.22, determined for geometry optimized hydroxyacid molecules, that connect the bond lengths to the average Pauling electrostatic bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the two sets of equations connecting ?(rc) and the Pauling bond strength s with bond length, it appears that Pauling’s simple definition of bond strength closely mimics the accumulation of the electron density between bonded pairs of atoms. The similarity of the expressions for the crystals and molecules is compelling evidence that the M-O bonded interactions for the crystals and molecules 2 containing the same bonded interactions are comparable. Similar expressions, connecting bond lengths and bond strength, have also been found to hold for fluoride, nitride and sulfide molecules and crystals. The Brown-Shannon bond valence, ?, power law expression ? = [R1/(R(M-O)]N that has found wide use in crystal chemistry, is shown to be connected to a more universal expression determined for oxides and the perovskites, = r[(1.41)/]4.76, demonstrating that the bond valence for a bonded interaction is likewise closely connected to the accumulation of the electron density between the bonded atoms. Unlike the Brown-Shannon expression, it is universal in that it holds for the M-O bonded interactions for a relatively wide range of M atoms of the periodic table. The power law equation determined for the oxide crystals at ambient conditions is similar to the power law expression = r[1.46/]5.26 determined for the perovskites at pressures as high as 80 GPa, indicating that the intrinsic connection between R(M-O) and ?(rc) that holds at ambient conditions also holds, to a first approximation, at high pressures.

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

2014-01-18

93

The influence of spectral nudging in simulating individual Vb-events with COSMO-CLM  

NASA Astrophysics Data System (ADS)

In previous studies certain European cyclones have been investigated in terms of related extreme precipitation events in Austria. Those systems passing the Mediterranean are of special interest as the atmospheric moisture content is increased. It has been shown in recent investigations that state-of-the-art RCMs can approximately reproduce observed heavy precipitation characteristics. This provides a basic confidence in the models ability to capture future changes of such events under increased greenhouse gas conditions as well. In this contribution we focus on high spatial and temporal scales and assess the currently achievable accuracy in the simulation of Vb-events. The state-of-the-art regional climate model CCLM is applied in a hindcast-mode to the case of individual Vb-events in August 2002 and Mai/June 2013. Besides the conventional forcing of the regional climate model at its lateral boundaries a spectral nudging technique is applied. This means that inside the model area the regional model is forced to accept the analysis for large scales whereas it has no effect on the small scales. The simulations for the Vb-events mentioned above covering the European domain have been varied systematically by changing nudging factor, number of nudged waves, nudged variables, and other parameters. The resulting precipitation amounts have been compared to E-OBS gridded European precipitation data set and a recent high spatially resolved precipitation data set for Austria (GPARD-6). Varying the spectral nudging setup in the short-term Vb-cases helps us on one hand learn something about 3D-processes during Vb-events e.g. vorticity and formation but on the other hand identify the model deficiencies. The results show, that increasing the number of nudged waves from 1 to 7 as well as the choice of the variables used in the nudging process have a large influence on the development of the low pressure system and the related precipitation patterns. On the contrary, the nudging factor or the definition of the uppermost pressure level for the nudging are of low impact on the results.

Paumann, Manuela; Anders, Ivonne; Hofstätter, Michael; Chimani, Barbara

2014-05-01

94

Bonding and phase transitions in transition metal dichalcogenide layer compounds  

Microsoft Academic Search

The electronic structure of the transition metal dichalcogenide layer compounds is studied using hybridised orbitals appropriate to the transition metal atom coordination. Non-bonding orbitals on the transition metal atoms give the conduction electron bands which are responsible for the charge-density-wave phase transitions in the VB compounds, and the band structure of 1T- and 2H-TaS2 is found using tight binding. The

J. E. Inglesfield

1980-01-01

95

X-ray imaging of chemically active valence electrons during a pericyclic reaction  

NASA Astrophysics Data System (ADS)

Time-resolved imaging of chemically active valence electron densities is a long-sought goal, as these electrons dictate the course of chemical reactions. However, X-ray scattering is always dominated by the core and inert valence electrons, making time-resolved X-ray imaging of chemically active valence electron densities extremely challenging. Here we demonstrate an effective and robust method, which emphasizes the information encoded in weakly scattered photons, to image chemically active valence electron densities. The degenerate Cope rearrangement of semibullvalene, a pericyclic reaction, is used as an example to visually illustrate our approach. Our work also provides experimental access to the long-standing problem of synchronous versus asynchronous bond formation and breaking during pericyclic reactions.

Bredtmann, Timm; Ivanov, Misha; Dixit, Gopal

2014-11-01

96

X-ray imaging of chemically active valence electrons during a pericyclic reaction.  

PubMed

Time-resolved imaging of chemically active valence electron densities is a long-sought goal, as these electrons dictate the course of chemical reactions. However, X-ray scattering is always dominated by the core and inert valence electrons, making time-resolved X-ray imaging of chemically active valence electron densities extremely challenging. Here we demonstrate an effective and robust method, which emphasizes the information encoded in weakly scattered photons, to image chemically active valence electron densities. The degenerate Cope rearrangement of semibullvalene, a pericyclic reaction, is used as an example to visually illustrate our approach. Our work also provides experimental access to the long-standing problem of synchronous versus asynchronous bond formation and breaking during pericyclic reactions. PMID:25424639

Bredtmann, Timm; Ivanov, Misha; Dixit, Gopal

2014-01-01

97

Cluster molecular orbital description of the electronic structures of mixed-valence iron oxides and silicates  

USGS Publications Warehouse

A molecular orbital description, based on spin-unrestricted X??-scattered wave calculations, is given for the electronic structures of mixed valence iron oxides and silicates. The cluster calculations show that electron hopping and optical intervalence charge-transger result from weak FeFe bonding across shared edges of FeO6 coordination polyhedra. In agreement with Zener's double exchange model, FeFe bonding is found to stabilize ferromagnetic coupling between Fe2+ and Fe3+ cations. ?? 1986.

Sherman, D.M.

1986-01-01

98

Solving the Puzzle of Tetratomic, 23-VALENCE-ELECTRON Molecules  

NASA Astrophysics Data System (ADS)

Because of extensive electron correlation, the ground-state structures, infrared spectra, and chemical bonding properties of a number of tetratomic molecules which possess 23 valence electrons are anomalous. Approaches which have recently been helpful in understanding this phenomenon include ab initio calculations and spectroscopic observations of these species trapped in solid neon at temperatures near 4 K. Molecules for which infrared spectra have been obtained and which will be discussed include NO_3, NNO2 anion, BF3 cation, and O4 cation.

Jacox, Marilyn E.

2010-06-01

99

Bent Bonds and Multiple Bonds.  

ERIC Educational Resources Information Center

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

Robinson, Edward A.; Gillespie, Ronald J.

1980-01-01

100

Asymptotic analysis of steady solutions of the KdVB equation with application to resonant sloshing  

NASA Astrophysics Data System (ADS)

The forced Korteweg-de Vries equation with Burgers’ damping (fKdVB) on a periodic domain, which arises as a model for water waves in a shallow tank with forcing near resonance, is considered. A method for construction of asymptotic solutions is presented, valid in cases where dispersion and damping are small. Through variation of a detuning parameter, families of resonant solutions are obtained providing detailed insight into the resonant response character of the system and allowing for direct comparison with the experimental results of Chester and Bones (1968).

Amundsen, D. E.; Cox, E. A.; Mortell, M. P.

2007-11-01

101

Sodium-sulfur battery development. Phase VB final report, October 1, 1981--February 28, 1985  

SciTech Connect

This report describes the technical progress made under Contract No. DE-AM04-79CH10012 between the U.S. Department of Energy, Ford Aerospace & Communications Corporations and Ford Motor Company, for the period 1 October 1981 through 28 February 1985, which is designated as Phase VB of the Sodium-Sulfur Battery Development Program. During this period, Ford Aerospace held prime technical responsibility and Ford Motor Company carried out supporting research. Ceramatec, Inc., was a major subcontractor to Ford Aerospace for electrolyte development and production.

NONE

1985-04-01

102

Investigation on the valence-band structure of ferromagnetic-semiconductor GaMnAs using spin-dependent resonant tunneling spectroscopy  

NASA Astrophysics Data System (ADS)

We investigate the valence-band (VB) structure of ferromagnetic-semiconductor GaMnAs by analyzing the resonant tunneling levels of a GaMnAs quantum well (QW) in double-barrier heterostructures. The resonant level from the heavy-hole first state (HH1) is clearly observed in the metallic GaMnAs QW with the Curie temperature of 60 K, which indicates that no holes reside in the VB of GaMnAs in the equilibrium condition. Clear enhancement of tunnel magnetoresistance induced by resonant tunneling is demonstrated. We find that the resonant levels formed in the GaMnAs QW are well explained by using the transfer matrix method with the 6x6 Luttinger-Kohn kp Hamiltonian, p-d exchange Hamiltonian, and Bir-Pikus strain Hamiltonian. The VB structure of GaMnAs is well reproduced by that of GaAs with a small exchange splitting energy of 3-5 meV and with the Fermi level lying at ˜30 meV higher than HH1 in the bandgap. This work was partly supported by Grant-in-Aids for Scientific Research, the Special Coordination Programs for Promoting Science and Technology, R&D for Next-generation Information Technology by MEXT, and PRESTO of JST.

Ohya, Shinobu; Muneta, Iriya; Hai, Pham Nam; Tanaka, Masaaki

2010-03-01

103

Myosin Vb Mediated Plasma Membrane Homeostasis Regulates Peridermal Cell Size and Maintains Tissue Homeostasis in the Zebrafish Epidermis  

PubMed Central

The epidermis is a stratified epithelium, which forms a barrier to maintain the internal milieu in metazoans. Being the outermost tissue, growth of the epidermis has to be strictly coordinated with the growth of the embryo. The key parameters that determine tissue growth are cell number and cell size. So far, it has remained unclear how the size of epidermal cells is maintained and whether it contributes towards epidermal homeostasis. We have used genetic analysis in combination with cellular imaging to show that zebrafish goosepimples/myosin Vb regulates plasma membrane homeostasis and is involved in maintenance of cell size in the periderm, the outermost epidermal layer. The decrease in peridermal cell size in Myosin Vb deficient embryos is compensated by an increase in cell number whereas decrease in cell number results in the expansion of peridermal cells, which requires myosin Vb (myoVb) function. Inhibition of cell proliferation as well as cell size expansion results in increased lethality in larval stages suggesting that this two-way compensatory mechanism is essential for growing larvae. Our analyses unravel the importance of Myosin Vb dependent cell size regulation in epidermal homeostasis and demonstrate that the epidermis has the ability to maintain a dynamic balance between cell size and cell number. PMID:25233349

Phatak, Mandar; Banerjee, Shamik; Mulay, Aditya; Deshpande, Ojas; Bhide, Sourabh; Jacob, Tressa; Gehring, Ines; Nuesslein-Volhard, Christiane; Sonawane, Mahendra

2014-01-01

104

On Lexicalized Valency and the Valency of (New) Complex Verbal Formations in Slovenian  

E-print Network

The paper considers the matter of so-called lexicalized valency within the framework of new complex verbal formations in Slovenian, and in consequence, the increasingly dominant accusative valency in the language, which can also indicate...

Žele, Andreja

2013-01-01

105

Valence atom with bohmian quantum potential: the golden ratio approach  

PubMed Central

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). PMID:23146157

2012-01-01

106

UV photoelectron spectroscopy at near ambient pressures: mapping valence band electronic structure changes from Cu to CuO.  

PubMed

Valence band (VB) changes and hence electronic structure evolution was directly observed with low kinetic energy (KE) electrons at near ambient pressure (NAP) conditions with He I photon source in a custom built laboratory ambient pressure photoelectron spectrometer (Lab-APPES). Polycrystalline Cu surfaces were gradually oxidized in O2 to Cu2O, to a mixture of Cu2O + CuO, and finally to CuO between 300 and 625 K and at NAP. Typical VB features for Cu, Cu2O, and CuO were observed, and the results corroborate well with core level and Auger spectral changes. High mean free path associated with low KE electrons, very low or no inelastic scattering, and effective pumping and the design of electrostatic lens regime help to minimize the electron attenuation at NAP conditions. The present results extend the capabilities of the APPES tool to explore the in situ evolution of electronic structure of materials at NAP and high temperatures. PMID:24601627

Roy, Kanak; Gopinath, Chinnakonda S

2014-04-15

107

30 CFR 57.22231 - Actions at 0.25 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Actions at 0.25 percent methane (I-B, II-B, V-B, and VI mines...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22231 Actions at 0.25 percent methane (I-B, II-B, V-B, and VI...

2010-07-01

108

30 CFR 57.22231 - Actions at 0.25 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Actions at 0.25 percent methane (I-B, II-B, V-B, and VI mines...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22231 Actions at 0.25 percent methane (I-B, II-B, V-B, and VI...

2011-07-01

109

30 CFR 57.22238 - Actions at 2.0 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Actions at 2.0 percent methane (I-B, II-B, V-B, and VI mines...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22238 Actions at 2.0 percent methane (I-B, II-B, V-B, and VI...

2011-07-01

110

30 CFR 57.22238 - Actions at 2.0 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Actions at 2.0 percent methane (I-B, II-B, V-B, and VI mines...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22238 Actions at 2.0 percent methane (I-B, II-B, V-B, and VI...

2010-07-01

111

Crossover from impurity to valence band in diluted magnetic semiconductors: Role of Coulomb attraction by acceptors  

SciTech Connect

The crossover between an impurity band (IB) and a valence band (VB) regime as a function of the magnetic impurity concentration in a model for diluted magnetic semiconductors (DMSs) is studied systematically by taking into consideration the Coulomb attraction between the carriers and the magnetic impurities. The density of states and the ferromagnetic transition temperature of a spin-fermion model applied to DMSs are evaluated using dynamical mean-field theory and Monte Carlo (MC) calculations. It is shown that the addition of a square-well-like attractive potential can generate an IB at small enough Mn doping x for values of the p-d exchange J that are not strong enough to generate one by themselves. We observe that the IB merges with the VB when x>=xc where xc is a function of J and the Coulomb strength V. Using MC simulations, we demonstrate that the range of the Coulomb attraction plays an important role. While the on-site attraction, which has been used in previous numerical simulations, effectively renormalizes J for all values of x, an unphysical result, a nearest-neighbor range attraction renormalizes J only at very low dopings, i.e., until the bound holes wave functions start to overlap. Thus, our results indicate that the Coulomb attraction can be neglected to study Mn-doped GaSb, GaAs, and GaP in the relevant doping regimes, but it should be included in the case of Mn-doped GaN, which is expected to be in the IB regime.

Popescu, Florentin [Florida State University; Sen, Cengiz [Florida State University; Dagotto, Elbio R [ORNL; Moreo, Adriana [ORNL

2007-01-01

112

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

PubMed

Electron-deficient covalent bonds are a type of covalent bonds without electron accumulation at their bonding regions. Compared with normal covalent bonds, they are quite sensitive to chemical environments. Electron-deficient and normal covalent bonds are not isolated from each other. An electron-deficient bond may change to a normal one upon the change of substituting groups. Neither bond elongation nor atom electronegativity is directly related to the electron deficiency in an electron-deficient bond. Atoms in molecules (AIM) analyses suggest that electron-deficient bonds are characterized by positive Laplacians and small ?(BCP) values. The positive Laplacian is caused by insignificant electron accumulation perpendicular to the bond path. On the basis of electron localization function (ELF) descriptors, electron-deficient bonds have small basin populations, low ? values and high relative fluctuations. There may be one or two bond basins for an electron-deficient bond. In addition, such a bond may correlate with two more valence basins close to the two participating atoms. Electron-deficient bonds are usually weak and long. This is consistent with the low s characters in their natural bond orbitals (NBOs). PMID:23009383

Yang, Yang

2012-10-18

113

Oxidation electronics: bond–band–barrier correlation and its applications  

Microsoft Academic Search

This report features the recent progress in understanding the behaviour of atoms and valence electrons involved in the process of oxidation, and some technological development driven by the new knowledge. It is initiated and verified that a chemical bond contracts spontaneously at a surface associated with magnitude rise of the bond energy due to the coordination imperfection and that an

Chang Q. Sun

2003-01-01

114

SEPARATION OF VARIABLES AND THE XXZ GAUDIN MAGNET E.G. KALNINS, V.B. KUZNETSOV and WILLARD MILLER, Jr.  

E-print Network

SEPARATION OF VARIABLES AND THE XXZ GAUDIN MAGNET E.G. KALNINS, V.B. KUZNETSOV and WILLARD MILLER, Minnesota 55455, USA. Abstract. In this work we generalise previous results connecting (rational) Gaudin the relationship between the separable systems and the Gaudin magnet [4,9] integrable systems models has been

115

SEPARATION OF VARIABLES AND THE XXZ GAUDIN MAGNET E.G. KALNINS, V.B. KUZNETSOV and WILLARD MILLER, Jr.  

E-print Network

SEPARATION OF VARIABLES AND THE XXZ GAUDIN MAGNET E.G. KALNINS, V.B. KUZNETSOV and WILLARD MILLER, Minnesota 55455, USA. Abstract. In this work we generalise previous results connecting (rational) Gaudin between the separable systems and the Gaudin magnet [4,9] integrable systems models has been established

116

Valence-band structure of the ferromagnetic semiconductor GaMnAs investigated by resonant tunneling spectroscopy  

NASA Astrophysics Data System (ADS)

The origin of ferromagnetism in the prototype ferromagnetic semiconductor GaMnAs is still controversial due to the insufficient understanding of its band structure and Fermi level position. Here, we investigate the valence-band (VB) structure of GaMnAs by analyzing the resonant tunneling levels of the GaMnAs quantum well (QW) in double-barrier heterostructures. The resonant levels including the heavy-hole first state (HH1) are clearly observed in the metallic GaMnAs QW with the Curie temperature (T/C) of 60 K, which indicates that no holes reside in the VB of GaMnAs in the equilibrium condition. Clear enhancement of tunnel magnetoresistance induced by resonant tunneling is demonstrated. We find that the resonant levels formed in the GaMnAs QW are well explained by using the transfer matrix method with the 6x6 {kp} Hamiltonian and small p-d exchange Hamiltonian. The VB structure of GaMnAs is well reproduced by that of GaAs with a small exchange splitting energy of 3-5 meV and with the Fermi level lying at ˜ 30 meV higher than HH1 in the bandgap. Furthermore, we show our more recent results of resonant tunneling spectroscopy on various surface GaMnAs films (Mn concentration: 6-15/, T/C: 71-154 K) grown on an AlAs layer, where the resonant levels are formed by confinement of the VB holes by the surface Schottky barrier and the AlAs barrier. We systematically investigate the thickness dependence of the resonant levels in GaMnAs by precisely etching the surface of GaMnAs. We find that the p-d exchange interaction is negligibly small (3-5 meV) and that the Fermi level exists in the bandgap. This work was performed in collaboration with I. Muneta, P. N. Hai, K. Takata, and M. Tanaka, and partly supported by Grant-in-Aids for Scientific Research, the Special Coordination Programs for Promoting Science and Technology, and FIRST Program by JSPS.[4pt] [1] S. Ohya et al., Phys. Rev. Lett. 104, 167204 (2010).[0pt] [2] S. Ohya et al., arXiv:1009.2235.

Ohya, Shinobu

2011-03-01

117

Action versus valence in decision making  

PubMed Central

The selection of actions, and the vigor with which they are executed, are influenced by the affective valence of predicted outcomes. This interaction between action and valence significantly influences appropriate and inappropriate choices and is implicated in the expression of psychiatric and neurological abnormalities, including impulsivity and addiction. We review a series of recent human behavioral, neuroimaging, and pharmacological studies whose key design feature is an orthogonal manipulation of action and valence. These studies find that the interaction between the two is subject to the critical influence of dopamine. They also challenge existing views that neural representations in the striatum focus on valence, showing instead a dominance of the anticipation of action. PMID:24581556

Guitart-Masip, Marc; Duzel, Emrah; Dolan, Ray; Dayan, Peter

2014-01-01

118

Nature of the Frequency Shift of Hydrogen Valence Vibrations  

E-print Network

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.

Zhyganiuk, I V

2015-01-01

119

Cu 2p Photoelectron and 2p 3/2-Valence-Valence Auger Electron Spectra of Cuprate Superconductors  

NASA Astrophysics Data System (ADS)

We have observed many-body effects in both the Cu 2p photoelectron and 2p3/2- valence-valence (L3VV) Auger electron spectra for thin films of Bi2Sr2Ca xCu1+ xO6+2 x (x=0, 1, 2), La2- xSr xCuO4 (x=0, 0.13), and ErBa2Cu3O7- x, y (x to |cd9> lines in the 2p spectra corresponded with an increase of the mixing of |d8L> and |d7> states in the L3VV spectra. Enlargement of the parameters of many-body effects resulted from an increase in covalency of the Cu O bond. An enlargement of the transfer integral is required for realization of high-T c superconductivity of Bi Sr Ca Cu O and La Sr Cu O systems. The 90 K superconductivity in Er Ba Cu O and Y Ba Cu O systems was realized by increasing the charge transfer energy.

Kohiki, Shigemi; Mizuno, Koichi; Enokihara, Akira; Hayashi, Shigenori; Sakai, Masahiro; Setsune, Kentaro; Fukushima, Sei; Gohshi, Yohichi

1994-12-01

120

Volume 34 | Issues 910 | 2013 Included in this print edition  

E-print Network

on the cover). The AMOEBA Polarizable Force Field The image shows a snapshot taken from an AMOEBA molecular on valence bond (VB) theory and incorporated into the AMOEBA polarizable force field. Gas phase calculations of ion-aqua complexes show that the proposed AMOEBA-VB model improves the accuracy of MM model energetics

Ponder, Jay

121

Subliminal Affect Valence Words Change Conscious Mood Potency but Not Valence: Is This Evidence for Unconscious Valence Affect?  

PubMed Central

Whether or not affect can be unconscious remains controversial. Research claiming to demonstrate unconscious affect fails to establish clearly unconscious stimulus conditions. The few investigations that have established unconscious conditions fail to rule out conscious affect changes. We report two studies in which unconscious stimulus conditions were met and conscious mood changes measured. The subliminal stimuli were positive and negative affect words presented at the objective detection threshold; conscious mood changes were measured with standard manikin valence, potency, and arousal scales. We found and replicated that unconscious emotional stimuli produced conscious mood changes on the potency scale but not on the valence scale. Were positive and negative affects aroused unconsciously, but reflected consciously in potency changes? Or were the valence words unconscious cognitive causes of conscious mood changes being activated without unconscious affect? A thought experiment is offered as a way to resolve this dilemma. PMID:24961258

Shevrin, Howard; Panksepp, Jaak; Brakel, Linda A. W.; Snodgrass, Michael

2012-01-01

122

Chemical bonding in hypervalent molecules. The dominance of ionic bonding and negative hyperconjugation over d-orbital participation  

Microsoft Academic Search

Does sulfur form six covalent bonds in CHâSOâCl, FâS{triple bond}N or carbon or phosphorus five bonds in FâC=O⁻, FâP=O After a brief history of the viewpoints on hypervalent bonding and a comparison of analysis methods (with CHâSOâCl as example), natural population and natural bond orbital analysis is applied to a series of 32-valence-electron species of XâXY type (CFâ, FâNO, OâClF,

Alan E. Reed; P. von Rague Schleyer

1990-01-01

123

Chemical vapor deposition of group IVb, Vb, and VIb elements with nonmetals. A literature review. Information circular  

SciTech Connect

The Bureau of Mines reviewed the chemical vapor deposition (CVD) literature on the nonmetal binary and ternary compounds of the group IVB, VB, and VIB elements, with emphasis directed to the following nonmetals: B, C, N, O, and Si. This review examines each of these binary and selected ternary compounds of the group IVB, VB, and VIB elements as coatings and gives some of their preparative methods, uses, and properties. A total of 259 references were found for these compounds of the nine elements. This review was utilized in the Bureau's research to provide abrasion-, erosion-, and corrosion-resistant coatings in order to conserve critical metals and protect various metallic surfaces in metallurgical, mining, and energy conversion systems.

McDonald, H.O.; Stephenson, J.B.

1983-05-01

124

Valence band and band gap photoemission study of (1 1 1) In 2O 3 epitaxial films under interactions with oxygen, water and carbon monoxide  

NASA Astrophysics Data System (ADS)

Synchrotron radiation ultraviolet photoemission experiments at photon energies of 150 and 49 eV were performed on an epitaxial layer of (1 1 1) In 2O 3 with good crystallinity as established by a standard scanning probe and diffraction methods. Valence band (VB) and band gap photoemission spectra were monitored under separate oxygen, water and carbon monoxide exposures (100 L) at different activation temperatures within the range utilized for chemiresistive gas sensors (160-450 °C). Large changes in photoemission response within the whole VB were observed for all gases. Regular shifts of the valence band edge relative to the Fermi energy were found under gas exposures on two kinds of surface (partially reduced or partially oxidized), and are interpreted as changes of surface potential. Treatments in oxygen resulted in upward band bending (˜0.5 eV at T = 320 °C). Regardless of activation temperature, treatments in water resulted in downward band bending, but with small changes (<0.1 eV). Reduction properties of carbon monoxide were observed only at high temperatures of T ? 370 °C. At temperatures of 160 and 250 °C unusual "oxidizing" behavior of CO was observed with upward band bending of ˜0.7 eV (160 °C). Oxidizing and reducing effects of the gas interactions with the (1 1 1) In 2O 3 surface in all cases were accompanied by a corresponding behavior, i.e., a decrease or increase in photoemission response from so-called defect states in the band gap near the top of the valence band. The increases of photoemission within a band gap with maxima at binding energies (BE) of 0.4 (O 2-induced peak) and 1.0 eV (CO-induced peak) were, respectively, found for interactions with O 2 and CO for low temperatures ( T = 160 and 250 °C). These responses were ascribed to acceptor-like electronic levels of O 2 and CO chemisorption states, respectively. A definite split of the top VB peak (BE ˜ 4.0 eV) was found under CO dosing at 160 °C. Established knowledge of the CO interaction with the (1 1 1) In 2O 3 surface explains earlier revealed acceptor-like behavior of In 2O 3 film conductivity during CO detection at operational temperatures lower than 250 °C through the formation of acceptor-like electronic levels of adsorbed CO molecules.

Brinzari, V.; Korotcenkov, G.; Ivanov, M.; Nehasil, V.; Matolin, V.; Mašek, K.; Kamei, M.

2007-12-01

125

Valence shell direct double photodetachment in polyanions  

NASA Astrophysics Data System (ADS)

A valence shell study of electrosprayed insulin protein polyanion photodetachment was carried out on a vacuum ultra-violet synchrotron radiation beamline coupled to a radiofrequency ion trap, for both close- and open-shell species. A two-electron photodetachment is observed, which arises from two different mechanisms that are disentangled: a sequential multi-photon absorption and a direct one-photon two-electron process. The threshold for the direct double-electron ejection is measured at 11.4 eV and corresponds to electronic excitation in the valence shell, which makes it the first observation of direct double photodetachment in the valence shell. The results are discussed in the light of previous knowledge from multiple photoionization and ab initio calculations on model polyanions. Double photodetachment appears to be a relaxation mechanism that leads to oxidized anions of striking stability, a feature of high relevance in radiobiology.

Brunet, Claire; Antoine, Rodolphe; Dugourd, Philippe; Duflot, Denis; Canon, Francis; Giuliani, Alexandre; Nahon, Laurent

2013-06-01

126

Removal of Vanadium from Molten Aluminum—Part II. Kinetic Analysis and Mechanism of VB2 Formation  

NASA Astrophysics Data System (ADS)

Transition metal impurities such as vanadium (V), titanium (Ti), zirconium (Zr), and chromium (Cr) reduce the electrical conductivity of smelter grade aluminum. These impurities are removed by the addition of boron-bearing substances (AlB12/AlB2) and the process is called boron treatment. The quality of the alloy and the economy of boron treatment can be improved by understanding the kinetics and mechanism of VB2 formation in molten aluminum. Currently, there is limited published information on the heterogeneous kinetics of the boron treatment. In this study, an investigation of the kinetics of V removal from molten Al-1 wt pct V alloys during boron treatment at 1023 K (750 °C) was carried out. The effects of stirring (natural, mechanical, and gas), reaction temperature, and the levels of boron addition were analyzed. The kinetics of the process could be described in two stages. The rate was faster in the early stage of reaction and was halted after 10 minutes. It was concluded that the early stage of reaction was controlled by the mass transfer of V in molten aluminum. In the second stage of reaction, it was concluded that the kinetics was controlled by the diffusion of B through a VB2 layer formed in the early stage of reaction. It was observed from microscopy analysis that the ring of VB2 disintegrated during gas stirring of bulk melt and consequently the kinetics of reaction was enhanced.

Khaliq, Abdul; Rhamdhani, Muhammad Akbar; Brooks, Geoffrey A.; Grandfield, John F.

2014-04-01

127

In vitro thrombolytic activity of purified streptokinase extracted from Streptococcus equinus VIT_VB2 isolated from bovine milk.  

PubMed

Streptokinase (SK) is an extracellular enzyme secreted by various strains of ?-hemolytic Streptococci. The main focus of the current study is to evaluate the in vitro thrombolytic activity of purified SK extracted from Streptococcus equinus VIT_VB2 (Accession no. JX406835) isolated from milk sample. The growth rate of S. equinus VIT_VB2 strain was studied with pH and biomass content which has positive significant effect on enzyme yield. A temperature of 10 °C and pH of 6 was found to be optimum for maximum SK activity. The specific activity of the purified SK produced by VIT_VB2 strain was found to be 6,585 IU mg(-1). The molecular mass of the enzyme was determined as 47 kDa by SDS-PAGE. In vitro thrombolytic activity of purified SK was determined using synthetic chromogenic substrate S-2251, the activity of the purified enzyme was found to be 6,330 ± 2.2 IU. The purity of SK was compared with standard SK by HPLC. This is the first report which reveals the SK activity of S. equinus isolated from milk sample. PMID:24897956

Babu, Vaishnavi; Subathra Devi, C

2014-06-01

128

Nature of valence transition and spin moment in Ag(n)V(+) clusters.  

PubMed

Evolution in the atomic structure, bonding characteristics, stability, and the spin magnetic moment of neutral and cationic AgnV clusters has been investigated using first-principles density functional approach with gradient corrected functional. It is shown that at small sizes, the V 4s states hybridize with Ag states to form 1S and 1P like superatomic orbitals, whereas the 3d states are localized on V giving the V atom an effective valence of 1 or 2. Starting from Ag8V(+), the V 3d states begin to participate in the bonding by hybridizing with the nearly free electron gas to form 1D superatomic orbitals increasing the V atom effective valence toward 5. For the cationic clusters, this changing valence results in three shell closures that lead to stable species. These occur for cationic clusters containing 5, 7, and 14 Ag atoms. The first two stable species correspond to filled 1S and 1P shells in two and three dimensions with a valence of 2 for V, whereas the closure at 14 Ag atoms correspond to filled 1S, 1P, and 1D shells with V site exhibiting a valence of 5. The transition from filled 1S and 1P shells to filled 1S, 1P, and 1D shells is confirmed by a quenching of the spin magnetic moment. The theoretical findings are consistent with the observed drops in intensity in the mass spectrum of AgnV(+) clusters after 5, 7, and 14 Ag atoms. PMID:24824084

Medel, Victor M; Reber, Arthur C; Chauhan, Vikas; Sen, Prasenjit; Köster, Andreas M; Calaminici, Patrizia; Khanna, Shiv N

2014-06-11

129

Fluctuating valence in a correlated solid and the anomalous properties of delta-plutonium.  

PubMed

Although the nuclear properties of the late actinides (plutonium, americium and curium) are fully understood and widely applied to energy generation, their solid-state properties do not fit within standard models and are the subject of active research. Plutonium displays phases with enormous volume differences, and both its Pauli-like magnetic susceptibility and resistivity are an order of magnitude larger than those of simple metals. Curium is also highly resistive, but its susceptibility is Curie-like at high temperatures and orders antiferromagnetically at low temperatures. The anomalous properties of the late actinides stem from the competition between itinerancy and localization of their f-shell electrons, which makes these elements strongly correlated materials. A central problem in this field is to understand the mechanism by which these conflicting tendencies are resolved in such materials. Here we identify the electronic mechanisms responsible for the anomalous behaviour of late actinides, revisiting the concept of valence using a theoretical approach that treats magnetism, Kondo screening, atomic multiplet effects and crystal field splitting on the same footing. We find that the ground state in plutonium is a quantum superposition of two distinct atomic valences, whereas curium settles into a magnetically ordered single valence state at low temperatures. The f(7) configuration of curium is contrasted with the multiple valences of the plutonium ground state, which we characterize by a valence histogram. The balance between the Kondo screening and magnetism is controlled by the competition between spin-orbit coupling, the strength of atomic multiplets and the degree of itinerancy. Our approach highlights the electronic origin of the bonding anomalies in plutonium, and can be applied to predict generalized valences and the presence or absence of magnetism in other compounds starting from first principles. PMID:17392780

Shim, J H; Haule, K; Kotliar, G

2007-03-29

130

Mixed Valence and Spin Fluctuations in Cerium  

NASA Astrophysics Data System (ADS)

The pseudobinary alloys Ce(Ni(,x)Co(,1-x))(,2), (Ce(,x)La(,1-x))Ni(,2) and (Ce(,x)Y(,1-x))Ni(,2), where 0 < x < 1, have been studied. The room temperature lattice constant, the magnetic susceptibility in the 6 to 300 K temperature range, the low temperature specific heat in the 0.4 to 25 K range and the electrical resistivity in the 0.4 to 300 K range were measured. Additionally, X -ray absorption around L(,3) edge has been studied using the synchroton radiation. Both, thermodynamic and L(,3) probes yield similar results for the changes of valence of Ce across these systems. We have established that Ce is in the saturated valence state in the Ce(Ni(,x)Co(,1 -x))(,2) for x < 0.25. The valence decreases with x in the 0.25 to 1 concentration range. Similarly, the valence of Ce decreases in the (Ce, Y)Ni(,2) systems upon substitution of Y for Ce. The results obtained for the (Ce(,x)La(,1 -x))Ni(,2) system are interpreted in terms of changes of the Ce('3+) impurity levels. Spin fluctuations due to the 3d electrons play an important role in these systems.

Andraka, Bohdan

131

Prospective memory, emotional valence, and multiple sclerosis  

Microsoft Academic Search

Cognitive impairments in multiple sclerosis (MS) extend to tasks demanding prospective memory (PM): remembering to perform an intended act during ongoing activity. This study investigated whether emotional content influenced the effects of MS on PM, following evidence that emotional valence can influence other aspects of memory. Thirty participants with MS were compared to 30 controls on a PM task, Virtual

Peter G. Rendell; Julie D. Henry; Louise H. Phillips; Xochitl de la Piedad Garcia; Patricia Booth; Patricia Phillips; Matthias Kliegel

2012-01-01

132

Improved Error Estimate for the Valence Approximation  

E-print Network

We construct a systematic mean-field-improved coupling constant and quark loop expansion for corrections to the valence (quenched) approximation to vacuum expectation values in the lattice formulation of QCD. Terms in the expansion are evaluated by a combination of weak coupling perturbation theory and a Monte Carlo algorithm.

W. Lee; D. Weingarten

1998-04-10

133

Myosin Vb uncoupling from RAB8A and RAB11A elicits microvillus inclusion disease.  

PubMed

Microvillus inclusion disease (MVID) is a severe form of congenital diarrhea that arises from inactivating mutations in the gene encoding myosin Vb (MYO5B). We have examined the association of mutations in MYO5B and disruption of microvillar assembly and polarity in enterocytes. Stable MYO5B knockdown (MYO5B-KD) in CaCo2-BBE cells elicited loss of microvilli, alterations in junctional claudins, and disruption of apical and basolateral trafficking; however, no microvillus inclusions were observed in MYO5B-KD cells. Expression of WT MYO5B in MYO5B-KD cells restored microvilli; however, expression of MYO5B-P660L, a MVID-associated mutation found within Navajo populations, did not rescue the MYO5B-KD phenotype but induced formation of microvillus inclusions. Microvilli establishment required interaction between RAB8A and MYO5B, while loss of the interaction between RAB11A and MYO5B induced microvillus inclusions. Using surface biotinylation and dual immunofluorescence staining in MYO5B-KD cells expressing mutant forms of MYO5B, we observed that early microvillus inclusions were positive for the sorting marker SNX18 and derived from apical membrane internalization. In patients with MVID, MYO5B-P660L results in global changes in polarity at the villus tips that could account for deficits in apical absorption, loss of microvilli, aberrant junctions, and losses in transcellular ion transport pathways, likely leading to the MVID clinical phenotype of neonatal secretory diarrhea. PMID:24892806

Knowles, Byron C; Roland, Joseph T; Krishnan, Moorthy; Tyska, Matthew J; Lapierre, Lynne A; Dickman, Paul S; Goldenring, James R; Shub, Mitchell D

2014-07-01

134

Effective valence shell interactions in carbon, nitrogen, and oxygen atoms  

Microsoft Academic Search

We present the first numerical results of the canonical transformation formalism for generating the valence shell effective interactions. Considering the valence space to be formed as the antisymmetrized direct product of 2s and 2p type orbitals we have computed all the matrix elements of the two-body valence shell interactions for isolated carbon, nitrogen, and oxygen atoms. Explicit forms for the

Paul Westhaus; E. G. Bradford

1975-01-01

135

A comparative study of dissociation of thymidine molecules following valence or core photoionization  

NASA Astrophysics Data System (ADS)

We have studied the fragmentation of gas phase thymidine following valence and core ionization using synchrotron radiation, combined with electron energy and ion mass resolved detection in coincidence. To identify certain fragment masses 13C labelled thymidine was also used. We find that in large part, the photofragmentation of thymidine can be described as separated thymine and 2-deoxy-d-ribose cations. However, also the intact thymidine radical cation, formation of intact base and sugar cations from glycosidic bond cleavage and several new thymidine-specific fragments are observed after valence ionization. Conversely, at the photoionization of C 1s electrons neither parent thymidine cations nor any fragments above 55 amu were detected, and only ion pairs with small masses survive core ionization, Auger decay and the subsequent Coulomb separation of the DNA sub-unit. This demonstrates the genotoxic nature of soft x-rays which in cells induce complex clustered damage similar to those yielded by heavy particles.

Itälä, E.; Huels, M. A.; Rachlew, E.; Kooser, K.; Hägerth, T.; Kukk, E.

2013-11-01

136

Formation of an unconventional Ag valence state in Ag2NiO2  

NASA Astrophysics Data System (ADS)

The Ag ion in the recently synthesized novel material Ag2NiO2 adopts an extremely unusual valency of (1)/(2) , leaving the Ni ion as 3+ , rather than the expected 2+ . Using first-principles calculations, we show that this mysterious subvalent state emerges due to a strong bonding-antibonding interaction between the two Ag layers that drives the lower band beneath the O p complex, eliminating the possibility of a conventional Ag 1+ valence state. The strong renormalization of the specific heat coefficient ? is likely due to strong spin fluctuations that stem from nearly complete compensation of the ferromagnetic (metallic double exchange and 90° superexchange) and antiferromagnetic (conventional superexchange via Ni-O-Ag-O-Ni path) interactions.

Johannes, M. D.; Streltsov, S.; Mazin, I. I.; Khomskii, D. I.

2007-05-01

137

Barrier-free proton transfer in the valence anion of 2'-deoxyadenosine-5'-monophosphate. II. A computational study  

NASA Astrophysics Data System (ADS)

The propensity of four representative conformations of 2'-deoxyadenosine-5'-monophosphate (5'-dAMPH) to bind an excess electron has been studied at the B3LYP /6-31++G(d,p) level. While isolated canonical adenine does not support stable valence anions in the gas phase, all considered neutral conformations of 5'-dAMPH form adiabatically stable anions. The type of an anionic 5'-dAMPH state, i.e., the valence, dipole bound, or mixed (valence/dipole bound), depends on the internal hydrogen bond(s) pattern exhibited by a particular tautomer. The most stable anion results from an electron attachment to the neutral syn-south conformer. The formation of this anion is associated with a barrier-free proton transfer triggered by electron attachment and the internal rotation around the C4'-C5' bond. The adiabatic electron affinity of the a&barbelow;south-syn anion is 1.19eV, while its vertical detachment energy is 1.89eV. Our results are compared with the photoelectron spectrum (PES) of 5'-dAMPH- measured recently by Stokes et al., [J. Chem. Phys. 128, 044314 (2008)]. The computational VDE obtained for the most stable anionic structure matches well with the experimental electron binding energy region of maximum intensity. A further understanding of DNA damage might require experimental and computational studies on the systems in which purine nucleotides are engaged in hydrogen bonding.

Koby?ecka, Monika; Gu, Jiande; Rak, Janusz; Leszczynski, Jerzy

2008-01-01

138

Valence skipping driven superconductivity and charge Kondo effect  

NASA Astrophysics Data System (ADS)

Valence skipping in metallic compounds can give rise to an unconventional superconductivity. Several elements in the periodic table show valence skipping (or valence missing), for example, Bi forms the compounds in valence states +3 and +5. The doping of valence skipping elements will induce superconductivity and this will lead to a possibility of high temperature superconductivity. We consider the Wolf model with negative-U impurities, and show a phase diagram including superconducting phase. The superconducting state is changed into a metallic state with a local singlet as the attractive interaction |U| increases. There is a high temperature region near the boundary.

Yanagisawa, Takashi; Hase, Izumi

2013-11-01

139

Comparative study on residual strain and thermal stress in 4-in GaAs crystals grown by LEC and VB techniques  

NASA Astrophysics Data System (ADS)

Residual strains of 4-in diameter GaAs crystals grown by liquid encapsulated Czochralski (LEC) and vertical Bridgman (VB) techniques have been measured by scanning infrared polariscope (SIRP). It was found that the residual strain of the substrate cut at the shoulder portion of a LEC-grown crystal was remarkably larger than that cut at the middle portion of the crystal. It was also found that the residual strains of the substrates cut at the shoulder and middle portions of a VB-grown crystal were both smaller than those of the LEC-grown crystal, and showed the similar values and profiles with each other. Von Mises stress and excess shear stress according to the Jordan's criterion were calculated to understand these experimental results. It was found that large thermal stress was caused during the LEC growth especially in the early stage, while thermal stresses caused during the VB growth were considerably smaller than those caused during the LEC growth from the shoulder to the middle. These experimental and analytical results suggest that the difference in the residual strain along the growth axis between LEC and VB crystals is due to the difference of the thermal stress caused during the crystal growth between LEC and VB techniques.

Kawase, Tomohiro; Tatsumi, Masami; Yamada, Masayoshi

2005-02-01

140

Syllabus CHEM 8833 1. Structure and Models of Bonding  

E-print Network

Syllabus CHEM 8833 1. Structure and Models of Bonding · Atomic structure · Quantum numbers and atomic orbitals · Lewis structures · Valence-shell electron pair repulsion rules · Hybridization structure theory · Larger molecules: Qualitative molecular orbital theory (QMOT) First Exam 2. Strain

Sherrill, David

141

Influence of valence, electronegativity, atomic radii, and crest-trough interaction with phonons on the high-temperature copper oxide superconductors  

SciTech Connect

Several structural features, including electron transfer between atoms of different electronegativity, oxygen deficiency, and unsynchronized resonance of valence bonds, as well as tight binding of atoms and the presence of both hypoelectronic and hyperelectronic elements, cooperatre to confer metallic properties and high-temperature superconductivity on compounds such as (Sr,Ba,Y,La)/sub 2/CuO/sub 4-//sub y/. .AE

Pauling, L.

1987-07-13

142

Goldstone Boson's Valence-Quark Distribution  

E-print Network

Dynamical chiral symmetry breaking (DCSB) is one of the keystones of low-energy hadronic phenomena. Dyson-Schwinger equations provide a model-independent quark-level understanding and correlate that with the behaviour of the pion's Bethe-Salpeter amplitude. This amplitude is a core element in the calculation of pion observables and combined with the dressed-quark Schwinger function required by DCSB it yields a valence-quark distribution function for the pion that behaves as (1-x)^2 for x~1, in accordance with perturbative analyses. This behaviour can be verified at contemporary experimental facilities.

C. D. Roberts

2001-11-12

143

Anomalous Eu valence state and superconductivity in undoped Eu3Bi2S4F4.  

PubMed

We have synthesized a novel europium bismuth sulfofluoride, Eu3Bi2S4F4, by solid-state reactions in sealed evacuated quartz ampules. The compound crystallizes in a tetragonal lattice (space group I4/mmm, a = 4.0771(1) Å, c = 32.4330(6) Å, and Z = 2), in which CaF2-type Eu3F4 layers and NaCl-like BiS2 bilayers stack alternately along the crystallographic c axis. There are two crystallographically distinct Eu sites, Eu(1) and Eu(2) at the Wyckoff positions 4e and 2a, respectively. Our bond valence sum calculation, based on the refined structural data, indicates that Eu(1) is essentially divalent, while Eu(2) has an average valence of ??+2.64(5). This anomalous Eu valence state is further confirmed and supported, respectively, by Mössbauer and magnetization measurements. The Eu(3+) components donate electrons into the conduction bands that are mainly composed of Bi 6px and 6py states. Consequently, the material itself shows metallic conduction and superconducts at 1.5 K without extrinsic chemical doping. PMID:25314008

Zhai, Hui-Fei; Zhang, Pan; Wu, Si-Qi; He, Chao-Yang; Tang, Zhang-Tu; Jiang, Hao; Sun, Yun-Lei; Bao, Jin-Ke; Nowik, Israel; Felner, Israel; Zeng, Yue-Wu; Li, Yu-Ke; Xu, Xiao-Feng; Tao, Qian; Xu, Zhu-An; Cao, Guang-Han

2014-10-29

144

Valence modulations in CeRuSn  

NASA Astrophysics Data System (ADS)

CeRuSn exhibits an extraordinary room temperature structure at 300 K with the coexistence of two types of Ce ions, namely trivalent Ce 3+ and intermediate-valent Ce(4-? )+, in a metallic environment. The ordered arrangement of these two Ce types on specific crystallographic sites results in a doubling of the unit cell along the c axis with respect to the basic monoclinic CeCoAl-type structure. Below room temperature, structural modulation transitions with very broad hysteresis have been reported from measurements of various bulk properties. X-ray diffraction revealed that at low temperatures the doubling of the CeCoAl-type structure is replaced by a different modulated ground state, approximating a near tripling of the basic CeCoAl cell. The transition is accompanied by a significant contraction of the c axis. We present new x-ray absorption near-edge spectroscopy data at the Ce L3 absorption edge, measured on a freshly cleaved surface of a CeRuSn single crystal. In contrast to our previous report, the new data exhibit small but significant variations as a function of temperature that are consistent with a transition of a fraction of Ce3+ ions to the intermediate valence state, analogous to the ? ?? transition in elemental cerium, when cooling through the structural transitions of CeRuSn. Such results in a valence-modulated state.

Feyerherm, R.; Dudzik, E.; Prokeš, K.; Mydosh, J. A.; Huang, Y.-K.; Pöttgen, R.

2014-07-01

145

Final report from VFL Technologies for the pilot-scale thermal treatment of Lower East Fork Poplar Creek floodplain soils. LEFPC Appendices, Volume 3, Appendix V-B  

SciTech Connect

This report consists of appendix V-B which contains the final verification run data package. Validation of analytical data is presented for Ecotek LSI. Analytical results are included of both soil and creek bed samples for the following contaminants: metals; metals (TCLP); uranium; gross alpha/beta; and polychlorinated biphenyls.

NONE

1994-09-01

146

VB-201, an oxidized phospholipid small molecule, inhibits CD14- and Toll-like receptor-2-dependent innate cell activation and constrains atherosclerosis  

PubMed Central

Atherosclerosis is an inflammatory disease of the vascular wall. Activated monocytes and dendritic cells (DC) in the intima layer of the vasculature promote atherogenesis. Toll-like receptor (TLR)-2 and TLR-4, which are predominantly expressed on these cells and mediate their activation, are essential for atherosclerosis development. In this study we demonstrate that VB-201, an oxidized phospholipid (Ox-PL) small molecule, inhibits TLR signalling restricted to TLR-2 and TLR-4 in human and mouse monocytes and DC. Mechanistically, we show that VB-201 binds directly to TLR-2 and CD14, the TLR-4 co-receptor, to impair downstream cues and cytokine production. In a rabbit model, oral administration of VB-201 constrained atherosclerosis progression. This effect was not due to reduced cholesterol abundance, as hyperlipidaemia was sustained. We suggest that VB-201 may counter inflammation where TLR-2 and/or CD14 complicity is essential, and is therefore beneficial for the treatment of atherosclerosis. PMID:24116867

Mendel, I; Feige, E; Yacov, N; Salem, Y; Levi, I; Propheta-Meiran, O; Shoham, A; Ishai, E; George, J; Harats, D; Breitbart, E

2014-01-01

147

30 CFR 57.22231 - Actions at 0.25 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2014 CFR

...percent methane (I-B, II-B, V-B, and VI mines). 57.22231 Section 57.22231 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2014-07-01

148

30 CFR 57.22232 - Actions at 0.5 percent methane (I-B, II-A, II-B, IV, V-B, and VI mines).  

Code of Federal Regulations, 2012 CFR

...I-B, II-A, II-B, IV, V-B, and VI mines). 57.22232 Section 57.22232 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

149

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2012 CFR

...methane (I-A, I-B, III, V-A, and V-B mines). 57.22234 Section 57.22234 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

150

30 CFR 57.22232 - Actions at 0.5 percent methane (I-B, II-A, II-B, IV, V-B, and VI mines).  

Code of Federal Regulations, 2014 CFR

...I-B, II-A, II-B, IV, V-B, and VI mines). 57.22232 Section 57.22232 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2014-07-01

151

30 CFR 57.22231 - Actions at 0.25 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2012 CFR

...percent methane (I-B, II-B, V-B, and VI mines). 57.22231 Section 57.22231 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

152

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2013 CFR

...methane (I-A, I-B, III, V-A, and V-B mines). 57.22234 Section 57.22234 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

153

30 CFR 57.22238 - Actions at 2.0 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2014 CFR

...percent methane (I-B, II-B, V-B, and VI mines). 57.22238 Section 57.22238 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2014-07-01

154

30 CFR 57.22238 - Actions at 2.0 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2013 CFR

...percent methane (I-B, II-B, V-B, and VI mines). 57.22238 Section 57.22238 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

155

30 CFR 57.22238 - Actions at 2.0 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2012 CFR

...percent methane (I-B, II-B, V-B, and VI mines). 57.22238 Section 57.22238 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

156

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2014 CFR

...methane (I-A, I-B, III, V-A, and V-B mines). 57.22234 Section 57.22234 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2014-07-01

157

30 CFR 57.22231 - Actions at 0.25 percent methane (I-B, II-B, V-B, and VI mines).  

Code of Federal Regulations, 2013 CFR

...percent methane (I-B, II-B, V-B, and VI mines). 57.22231 Section 57.22231 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

158

30 CFR 57.22232 - Actions at 0.5 percent methane (I-B, II-A, II-B, IV, V-B, and VI mines).  

Code of Federal Regulations, 2013 CFR

...I-B, II-A, II-B, IV, V-B, and VI mines). 57.22232 Section 57.22232 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

159

Teaching Valence Shell Electron Pair Repulsion (VSEPR) Theory  

ERIC Educational Resources Information Center

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),…

Talbot, Christopher; Neo, Choo Tong

2013-01-01

160

Core Polarization with Variable Oscillator Length Parameters for Valence Particles  

E-print Network

We study quadrupole and monopole core polarization using harmonic oscillator wave functions but with different length parameters for the valence particle as compared to the core. We use perturbation theory with a delta interaction. The results also hold for a density dependent delta interaction [1]. We study how the amount of core polarization varies with the distance of the valence particle from the core

Larry Zamick

2010-06-03

161

Core Polarization with Variable Length Parameters for Valence Particles  

E-print Network

We study quadrupole and monopole core polarization using harmonic oscillator wave funtions but with different length parameters for the valence particle as compared to the core. We use perturbation theory with a delta interaction. The results also hold for a density dependent delta interaction [1]. We study how the amount of core polarization varies with the distance of the valence particle from the core.

Larry Zamick

2010-05-27

162

Bonded Lubricants  

NASA Technical Reports Server (NTRS)

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

1977-01-01

163

Valence-electron spectral change and charge transfer mechanism of CaSi 2 during CaSi 2?H 2O reaction  

NASA Astrophysics Data System (ADS)

The changes in the valence electron states of CaSi 2 during the chemical reaction with H 2O have been investigated by Auger valence electron spectroscopy (AVES). The drastic changes in the valence electron spectra of 3s and 3p states, which are caused by the oxidization of the Si atoms in CaSi 2, were observed in Si[2s, 2p, V] spectra for CaSi 2 after the reaction. In particular, the Si[2s, 2p, V] spectra of CaSi 2 samples reacted with H 2O at 60 or 80°C for 3 h were almost similar to that of SiO 2. The peak shift of Ca[2p, 3p, 3p] Auger transition toward the lower energy side has been observed, suggesting the formation of bonds between Ca 3p and O orbitals. New peaks due to Ca?O or Ca?OH bonds also appeared in the valence electron region of Ca[2p, 3p, V] Auger transition. The charge transfer and the chemical-bond formation can be well demonstrated by AVES during the CaSi 2?H 2O reaction.

Abe, S.; Nakayama, H.; Nishino, T.; Iida, S.

1997-04-01

164

Charge Fluctuations and the Valence Transition in Yb under Pressure  

SciTech Connect

We present a dynamical mean field theory study of the valence transition (f{sup 14} {yields} f{sup 13}) in elemental, metallic Yb under pressure. Our calculations reproduce the observed valence transition as reflected in the volume dependence of the 4f occupation. The transition is accelerated by heating, and suggests quasiparticle or Kondo-like structure in the spectra of the trivalent end state, consistent with the early lanthanides. Results for the local charge fluctuations and susceptibility, however, show novel signatures uniquely associated with the valence transition itself, indicating that Yb is a fluctuating valence material in contrast to the intermediate valence behavior seen in the early trivalent lanthanides Ce, Pr, and Nd.

Ylvisaker, E R; Kunes, J; McMahan, A K; Pickett, W E

2009-04-21

165

Study of iron dimers reveals angular dependence of valence-to-core X-ray emission spectra.  

PubMed

Transition-metal K? X-ray emission spectroscopy (XES) is a developing technique that probes the occupied molecular orbitals of a metal complex. As an element-specific probe of metal centers, K? XES is finding increasing applications in catalytic and, in particular, bioinorganic systems. For the continued development of XES as a probe of these complex systems, however, the full range of factors which contribute to XES spectral modulations must be explored. In this report, an investigation of a series of oxo-bridged iron dimers reveals that the intensity of valence-to-core features is sensitive to the Fe-O-Fe bond angle. The intensity of these features has a well-known dependence on metal-ligand bond distance, but a dependence upon bond angle has not previously been documented. Herein, we explore the angular dependence of valence-to-core XES features both experimentally and computationally. Taken together, these results show that, as the Fe-O-Fe angle decreases, the intensity of the K?? feature increases and that this effect is modulated by increasing amounts of Fe np mixing into the O 2s orbital at smaller bond angles. The relevance of these findings to the identification of oxygenated intermediates in bioinorganic systems is highlighted, with special emphasis given to the case of soluble methane monooxygenase. PMID:25211540

Pollock, Christopher J; Lancaster, Kyle M; Finkelstein, Kenneth D; DeBeer, Serena

2014-10-01

166

Inelastic neutron scattering in valence fluctuation compounds  

SciTech Connect

The valence fluctuation compounds are rare earth intermetallics where hybridization of the nearly-localized 4f electrons with the conduction electrons leads to incorporation of the 4f's into the itinerant states. This hybridization slows down the conduction electrons and hence gives them a heavy effective mass, justifying application of the term 'heavy Fermion' (HF) to these materials. During the project period, we grew large single crystals of several such compounds and measured their properties using both standard thermodynamic probes and state-of-the-art inelastic neutron scattering. We obtained three main results. For the intermediate valence compounds CePd{sub 3} and YbAl{sub 3}, we showed that the scattering of neutrons by the fluctuations of the 4f magnetic moment does not have the momentum dependence expected for the itinerant heavy mass state; rather, the scattering is more typical of a localized spin fluctuation. We believe that incoherent scattering localizes the excitation. For the heavy Fermion compound Ce(Ni{sub 0.935}Pd{sub 0.065}){sub 2}Ge{sub 2}, which sits at a T = 0 critical point for transformation into an antiferromagnetic (AF) phase, we showed that the scattering from the AF fluctuations does not exhibit any of the divergences that are expected at a phase transition. We speculate that alloy disorder profoundly suppresses the growth of the fluctuating AF regions, leading to short range clusters rather than regions of infinite size. Finally, we explored the applicability of key concepts used to describe the behavior of rare earth heavy Fermions to uranium based HF compounds where the 5f electrons are itinerant as opposed to localized. We found that scaling laws relating the spin fluctuation energy measured in neutron scattering to the low temperature specific heat and susceptibility are valid for the uranium compounds, once corrections are made for AF fluctuations; however, the degeneracy of the high temperature moment is smaller than expected for rare-earth-like Hund's rule behavior, essentially because the orbital moment is suppressed for itinerant 5f electrons. We also found that the standard local-moment-based theory of the temperature dependence of the specific heat, susceptibility and neutron scattering fails badly for URu{sub 2}Zn{sub 20} and UCo{sub 2}Zn{sub 20}, even though the theory is phenomenally successful for the closely related rare earth compound YbFe{sub 2}Zn{sub 20}. Both these results highlight the distinction between the itineracy of the 5f's and the localization of the 4f's. It is our hope that these results are sufficiently significant as to stimulate deeper investigation of these compounds.

Jon M Lawrence

2011-02-15

167

NMR parameters and geometries of OHN and ODN hydrogen bonds of pyridine-acid complexes.  

PubMed

In this paper, equations are proposed which relate various NMR parameters of OHN hydrogen-bonded pyridine-acid complexes to their bond valences which are in turn correlated with their hydrogen-bond geometries. As the valence bond model is strictly valid only for weak hydrogen bonds appropriate empirical correction factors are proposed which take into account anharmonic zero-point energy vibrations. The correction factors are different for OHN and ODN hydrogen bonds and depend on whether a double or a single well potential is realized in the strong hydrogen-bond regime. One correction factor was determined from the known experimental structure of a very strong OHN hydrogen bond between pentachlorophenol and 4-methylpyridine, determined by the neutron diffraction method. The remaining correction factors which allow one also to describe H/D isotope effects on the NMR parameters and geometries of OHN hydrogen bond were determined by analysing the NMR parameters of the series of protonated and deuterated pyridine- and collidine-acid complexes. The method may be used in the future to establish hydrogen-bond geometries in biologically relevant functional OHN hydrogen bonds. PMID:15372662

Limbach, Hans-Heinrich; Pietrzak, Mariusz; Sharif, Shasad; Tolstoy, Peter M; Shenderovich, Ilya G; Smirnov, Sergei N; Golubev, Nikolai S; Denisov, Gleb S

2004-10-11

168

Chemical bonding in hypervalent molecules. The dominance of ionic bonding and negative hyperconjugation over d-orbital participation  

SciTech Connect

Does sulfur form six covalent bonds in CH{sub 3}SO{sub 2}Cl, F{sub 3}S{triple bond}N or carbon or phosphorus five bonds in F{sub 3}C=O{sup {minus}}, F{sub 3}P=O After a brief history of the viewpoints on hypervalent bonding and a comparison of analysis methods (with CH{sub 3}SO{sub 2}Cl as example), natural population and natural bond orbital analysis is applied to a series of 32-valence-electron species of X{sub 3}XY type (CF{sub 4}, F{sub 3}NO, O{sub 3}ClF, O{sub 3}PS{sup 3{minus}}, F{sub 3}SN, etc.). The {sigma}-bonding in these systems is found to be significantly ionic, and the strongly polar {sigma}*{sub AX} orbitals are found to be more effective electron acceptors than the extra-valence d{sub {pi}} (A) orbitals. By generalizing our discussion to n-coordinate 8n-valence-electron species (HF{sub 2}{sup {minus}}, BF{sub 3}, ClO{sub 4}{sup {minus}}, F{sub 4}SO, F{sub 5}TeO{sup {minus}}, IF{sub 6}{sup +}, OXeF{sub 6}, etc.) and their reduced analogues that have one or more lone pairs on the central atom (SF{sub 4}, IF{sub 6}{sup {minus}}, ClF{sub 3}, etc.), we provide a classification of hypervalent (and many nonhypervalent) molecules. The simple, qualitative bonding concepts for hypervalent molecules developed here supercede the inaccurate and misleading dsp{sup 3} and d{sup 2}sp{sup 3} models that are still in widespread use.

Reed, A.E.; von Rague Schleyer, P. (Universitaet Erlangen-Nuernberg (Germany, F.R.))

1990-02-14

169

Emotion and language: valence and arousal affect word recognition.  

PubMed

Emotion influences most aspects of cognition and behavior, but emotional factors are conspicuously absent from current models of word recognition. The influence of emotion on word recognition has mostly been reported in prior studies on the automatic vigilance for negative stimuli, but the precise nature of this relationship is unclear. Various models of automatic vigilance have claimed that the effect of valence on response times is categorical, an inverted U, or interactive with arousal. In the present study, we used a sample of 12,658 words and included many lexical and semantic control factors to determine the precise nature of the effects of arousal and valence on word recognition. Converging empirical patterns observed in word-level and trial-level data from lexical decision and naming indicate that valence and arousal exert independent monotonic effects: Negative words are recognized more slowly than positive words, and arousing words are recognized more slowly than calming words. Valence explained about 2% of the variance in word recognition latencies, whereas the effect of arousal was smaller. Valence and arousal do not interact, but both interact with word frequency, such that valence and arousal exert larger effects among low-frequency words than among high-frequency words. These results necessitate a new model of affective word processing whereby the degree of negativity monotonically and independently predicts the speed of responding. This research also demonstrates that incorporating emotional factors, especially valence, improves the performance of models of word recognition. PMID:24490848

Kuperman, Victor; Estes, Zachary; Brysbaert, Marc; Warriner, Amy Beth

2014-06-01

170

Valence band effective Hamiltonians in nitride semiconductors  

NASA Astrophysics Data System (ADS)

Valence band effective Hamiltonians are useful to determine the electronic states of shallow impurities, quantum wells, quantum wires and quantum dots within the effective mass approximation. Although significant experimental and theoretical work has been performed, basic parameters such as the Rashba Sheka Pikus (RSP) Hamiltonian parameters are still uncertain. In this work, the electronic band structures of AlN, GaN and InN, all in the wurtzite crystal structure, as well as the RSP Hamiltonian parameters are determined by using the QSGW approximation in a FP-LMTO implementation. The corrections offered by this approach beyond the LDA are important to obtain the splittings and effective masses accurately. The present GW implementation, which allows for a real space representation of the self-energy, enables us to interpolate exactly to a fine k-mesh and hence to obtain accurate effective masses. We find the crystal field splitting in GaN (12 meV) in much closer agreement with experiment than previous work and obtain a negative SO coupling for InN. Moreover, we have generalized the method of invariants to crystals with orthorombic symmetry, such as ZnSiN2 ZnGeN2, ZnSnN2 and CdGeN2 and determined the corresponding Hamiltonian parameters.

Punya, Atchara; Schwertfager, Nucharee; Lambrecht, Walter

2012-02-01

171

Valence fluctuation driven quantum phase transition  

NASA Astrophysics Data System (ADS)

In recent years quantum critical phenomenon have acquired a great interest in the condensed matter community. Many rare earth intermetallic compounds, which are also heavy fermions can be tuned easily to quantum critical point by application of external perturbations like magnetic field and pressure. YbRh2Si2 and CeCu2Si2 are a few examples. The periodic Anderson model (PAM) is a paradigm for studying these kind of systems. We investigate the extended periodic anderson model (EPAM), which includes Coulomb interaction of conduction and localised electrons using local moment approach (LMA) within dynamical mean field theory (DMFT) with the objective of developing an understanding of quantum phase transitions due to valence fluctuations. We show that tuning c-f interaction and on-site energy of localised electron (which can be achieved by varying external perturbation like pressure) leads to some exotic phenomena like vanishing of Fermi liquid scale. We study transport properties near quantum critical point and highlight the anomalies due to the proximity of QCP.

Kumar, Pramod; Vidhyadhiraja, N. S.

2012-02-01

172

Valence-orbital-electron momentum distributions for butanone  

NASA Astrophysics Data System (ADS)

We report here the measurements of the complete valence shell binding energy spectra and the valence-orbital momentum profiles of butanone using the binary (e,2e) electron momentum spectroscopy. The impact energy was 1200eV plus the binding energy and the symmetric noncoplanar kinematics was used. The experimental momentum profiles of the valence orbitals are compared with the theoretical momentum distributions calculated using Hartree-Fock and density functional theory methods with various basis sets. The experimental measurements are generally described by theoretical calculations except for summed 4a? , 15a' , 3a? , and 14a' orbital and summed 8a' , 7a' , and 6a' orbitals.

Li, G. Q.; Deng, J. K.; Li, B.; Ren, X. G.; Ning, C. G.

2005-12-01

173

PHYSICAL REVIEW B 88, 104102 (2013) Reinterpretation of the bond-valence model with bond-order formalism: An improved  

E-print Network

. INTRODUCTION The use of ferroelectric perovskite oxides in a variety of technological applications has prompted to a broad range of inorganic materials. DOI: 10.1103/PhysRevB.88.104102 PACS number(s): 07.05.Tp, 61.43.Bn I of the relationships between composition, structure, and properties.3­5 Despite the success of first-principles methods

Rappe, Andrew M.

174

On the bond distance in methane  

NASA Technical Reports Server (NTRS)

The equilibrium bond distance in methane was optimized using coupled-pair functional and contracted CI wave functions, and a Gaussian basis that includes g-type functions on carbon and d-type functions on hydrogen. The resulting bond distance, when corrected for core-valence correlation effects, agrees with the experimental value of 2.052 a(0) to within the experimental uncertainty of 0.002 a(0). The main source of error in the best previous studies, which showed discrepancies with experiment of 0.007 a(0) is shown to be basis set incompleteness. In particular, it is important that the basis set be close to saturation, at least for the lower angular quantum numbers.

Bowen-Jenkins, Philippa; Pettersson, Lars G. M.; Siegbahn, Per; Almloef, Jan; Taylor, Peter R.

1987-01-01

175

30 CFR 57.22227 - Approved testing devices (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2011 CFR

...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation...V-A, and V-B mines). (a) Methane monitoring devices and portable, battery-powered...self-contained devices used for measuring methane, other gases, and contaminants...

2011-07-01

176

30 CFR 57.22227 - Approved testing devices (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2010 CFR

...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation...V-A, and V-B mines). (a) Methane monitoring devices and portable, battery-powered...self-contained devices used for measuring methane, other gases, and contaminants...

2010-07-01

177

Valence state of Ti in conductive nanowires in sapphire  

NASA Astrophysics Data System (ADS)

In order to reveal the valence state of Ti in conductive nanowires in sapphire, near-edge x-ray-absorption fine structures (NEXAFS) were observed. From experimental and theoretical studies on NEXAFS of reference compounds including rutile, anatase, and Ti2O3 , it was found that the valence state of Ti can be identified by regarding the positions of the spectral onset and the shoulder in the main peak of Ti-K NEXAFS. The valence states of Ti doped Al2O3 polycrystalline specimens which were annealed at oxidized and reduced atmospheres were determined to be +4 and +3 , respectively. The solubility limit of Ti in Al2O3 polycrystal was found to be between 1000ppm to 1.0% at the both atmospheres. The spectrum from Ti nanowires in sapphire has a lot of similarities to the reduced specimen, the valence state was therefore concluded to be +3 .

Mizoguchi, Teruyasu; Sakurai, Masaki; Nakamura, Atsutomo; Matsunaga, Katsuyuki; Tanaka, Isao; Yamamoto, Takahisa; Ikuhara, Yuichi

2004-10-01

178

Psychological Bulletin The Relation Between Valence and Arousal in Subjective  

E-print Network

aspect of mind. As early as 1897, Wilhelm Wundt wrote that people are likely "never in a state entirely--are related to one another in subjective experience. Valence and Arousal Wundt (1912/1924) was among the first

Barrett, Lisa Feldman

179

A Valence Isomer Trapping Procedure for Introductory Organic Laboratory.  

ERIC Educational Resources Information Center

Described is an experiment which illustrates valence isomerization, the trapping of a reactive intermediate and retrosynthetic analysis applied to the Diels-Alder reaction. Included is a background discussion, experimental procedures, and a discussion of the analysis. (CW)

Kurtz, David W.; Johnson, Richard P.

1989-01-01

180

Bonding with Your Baby  

MedlinePLUS

... the child's social and cognitive development. Why Is Bonding Important? Bonding is essential for a baby. Studies ... as biological parents and their children. Back Continue Bonding With Daddy Men these days spend more time ...

181

What Determines Bond Costs. Municipal Bonds Series.  

ERIC Educational Resources Information Center

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

Young, Douglas; And Others

182

Valence state of Ti in conductive nanowires in sapphire  

Microsoft Academic Search

In order to reveal the valence state of Ti in conductive nanowires in sapphire, near-edge x-ray-absorption fine structures (NEXAFS) were observed. From experimental and theoretical studies on NEXAFS of reference compounds including rutile, anatase, and Ti2O3 , it was found that the valence state of Ti can be identified by regarding the positions of the spectral onset and the shoulder

Teruyasu Mizoguchi; Masaki Sakurai; Atsutomo Nakamura; Katsuyuki Matsunaga; Isao Tanaka; Takahisa Yamamoto; Yuichi Ikuhara

2004-01-01

183

Jornada d'ensenyament i s del valenci als  

E-print Network

Jornada d'ensenyament i ús del valencià als centres educatius 2014 Intercanvi d'experiències d'educació plurilingüe. ALACANT, 5 de juny de 2014 Lloc de realització: Universitat d'Alacant #12;Jornada d'ensenyament i ús del valencià als centres educatius 2014 Intercanvi d'experiències d'educació plurilingüe En un

Escolano, Francisco

184

Mixed-Valence Porphyrin ?-Cation Radical Derivatives: Electrochemical Investigations  

PubMed Central

The electrochemistry of [Cu(OEP)] and [Ni(OEP)] are compared with the mixed-valence ?-cations [Cu(OEP•/2)]2+and[Ni(OEP•/2)]2+. These electrochemical studies, carried out with cyclic voltametry and hydrodynamic voltametry, show that the mixed valence ?-cations have distinct electrochemical properties, although the differences between the [M(OEP)]+/0 and [M(OEP•/2)]2+/0 processes are subtle. PMID:19421310

Scheidt, W. Robert; Buentello, Kristin E.; Ehlinger, Noelle; Cinquantini, Arnaldo; Fontani, Marco; Laschi, Franco

2008-01-01

185

Bandlike valence states in d-AlNiCo Quasicrystals  

Microsoft Academic Search

A central question for quasicrystals (QCs) is the nature of the valence electronic states: whether or not they consist of Bloch-like states which are extended as in conventional periodic crystals. In this work we report the existence of extended band-like valence states in d-AlNiCo QCs. These states are measured using momentum (k)-resolved photoemission measurements on samples which were prepared by

K. Horn; Eli Rotenberg; W. Theis

2000-01-01

186

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

Code of Federal Regulations, 2013 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

2013-07-01

187

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

Code of Federal Regulations, 2010 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

2010-07-01

188

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

Code of Federal Regulations, 2012 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

2012-07-01

189

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

Code of Federal Regulations, 2011 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

2011-07-01

190

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

Code of Federal Regulations, 2014 CFR

...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules §...

2014-07-01

191

Emotional Valence and the Free-Energy Principle  

PubMed Central

The free-energy principle has recently been proposed as a unified Bayesian account of perception, learning and action. Despite the inextricable link between emotion and cognition, emotion has not yet been formulated under this framework. A core concept that permeates many perspectives on emotion is valence, which broadly refers to the positive and negative character of emotion or some of its aspects. In the present paper, we propose a definition of emotional valence in terms of the negative rate of change of free-energy over time. If the second time-derivative of free-energy is taken into account, the dynamics of basic forms of emotion such as happiness, unhappiness, hope, fear, disappointment and relief can be explained. In this formulation, an important function of emotional valence turns out to regulate the learning rate of the causes of sensory inputs. When sensations increasingly violate the agent's expectations, valence is negative and increases the learning rate. Conversely, when sensations increasingly fulfil the agent's expectations, valence is positive and decreases the learning rate. This dynamic interaction between emotional valence and learning rate highlights the crucial role played by emotions in biological agents' adaptation to unexpected changes in their world. PMID:23785269

Joffily, Mateus; Coricelli, Giorgio

2013-01-01

192

Chemical bonding in copper-based transparent conducting oxides: CuMO2 (M = In, Ga, Sc)  

NASA Astrophysics Data System (ADS)

The geometry and electronic structure of copper-based p-type delafossite transparent conducting oxides, CuMO2 (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 and conduction band edge explains the experimentally reported conductivity trends.

Godinho, K. G.; Morgan, B. J.; Allen, J. P.; Scanlon, D. O.; Watson, G. W.

2011-08-01

193

Chemical bonding in copper-based transparent conducting oxides: CuMO2 (M = In, Ga, Sc).  

PubMed

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 and conduction band edge explains the experimentally reported conductivity trends. PMID:21813950

Godinho, K G; Morgan, B J; Allen, J P; Scanlon, D O; Watson, G W

2011-08-24

194

Sequential and Prosodic Design of English and Greek Non-Valenced News Receipts  

ERIC Educational Resources Information Center

Results arising from a prosodic and interactional study of the organization of everyday talk in English suggest that news receipts can be grouped into two categories: valenced (e.g., "oh good") and non-valenced (e.g., "oh really"). In-depth investigation of both valenced and non-valenced news receipts shows that differences in their prosodic…

Kaimaki, Marianna

2012-01-01

195

Hard-Core Bosons on the Kagome Lattice: Valence-Bond Solids and Their Quantum Melting  

NASA Astrophysics Data System (ADS)

Using large scale quantum Monte Carlo simulations and dual vortex theory, we analyze the ground state phase diagram of hard-core bosons on the kagome lattice with nearest-neighbor repulsion. In contrast with the case of a triangular lattice, no supersolid emerges for strong interactions. While a uniform superfluid prevails at half filling, two novel solid phases emerge at densities ?=1/3 and ?=2/3. These solids exhibit an only partial ordering of the bosonic density, allowing for local resonances on a subset of hexagons of the kagome lattice. We provide evidence for a weakly first-order phase transition at the quantum melting point between these solid phases and the superfluid.

Isakov, S. V.; Wessel, S.; Melko, R. G.; Sengupta, K.; Kim, Yong Baek

2006-10-01

196

Hard-Core Bosons on the Kagome Lattice: Valence-Bond Solids and Their Quantum Melting  

Microsoft Academic Search

Using large scale quantum Monte Carlo simulations and dual vortex theory, we analyze the ground state phase diagram of hard-core bosons on the kagome lattice with nearest-neighbor repulsion. In contrast with the case of a triangular lattice, no supersolid emerges for strong interactions. While a uniform superfluid prevails at half filling, two novel solid phases emerge at densities rho=1\\/3 and

S. V. Isakov; S. Wessel; R. G. Melko; K. Sengupta; Yong Baek Kim

2006-01-01

197

Valence Bond Solids and Their Quantum Melting in Hard-Core Bosons on the Kagome Lattice  

Microsoft Academic Search

Using large scale quantum Monte Carlo simulations and dual vortex theory we\\u000aanalyze the ground state phase diagram of hard-core bosons on the kagome\\u000alattice with nearest neighbor repulsion. In contrast to the case of a\\u000atriangular lattice, no supersolid emerges for strong interactions. While a\\u000auniform superfluid prevails at half-filling, two novel solid phases emerge at\\u000adensities $\\\\rho=1\\/3$ and

S. V. Isakov; S. Wessel; R. G. Melko; K. Sengupta; Yong Baek Kim

2006-01-01

198

Extending first principles modeling with crystal chemistry: a bond-valence based classical  

E-print Network

, usually in the perovskite form, have been found favorable for many applications, such as ultrasound materials foruse in these applications, it is necessary to understand the inter-atomic interactions to be effective in determining the local structural properties of many of these materials. However, like many

Rappe, Andrew M.

199

2D multipartite valence bond states in quantum anti-ferromagnets  

SciTech Connect

A quantum anti-ferromagnetic spin-1 model is characterised on a 2D lattice with the following requirements: (i) The Hamiltonian is made out of nearest neighbour interactions. (ii) It is homogeneous, translational and rotational invariant. (iii) The ground state is a real singlet state of SU(2) (non-chiral). (iv) It has a local spin-1 representation. Along the way to characterise the system, connections with classical statistical mechanics and integrable models are explored. Finally, the relevance of the model in the physics of low dimensional anti-ferromagnetic Mott-Hubbard insulators is discussed.

Rico, E. [Institut fuer Theoretische Physik, Universitat Innsbruck, Technikerstrasse 25, A-6020 Innsbruck (Austria); Institute of Quantum Optics and Quantum Information of the Austrian Academy of Science, A-6020 Innsbruck (Austria); Fakultat fuer Physik, Universitat Wien, Boltzmanngasse 5, A-1090 Wien (Austria)], E-mail: enrique.ortega@univie.ac.at; Briegel, H.J. [Institut fuer Theoretische Physik, Universitat Innsbruck, Technikerstrasse 25, A-6020 Innsbruck (Austria); Institute of Quantum Optics and Quantum Information of the Austrian Academy of Science, A-6020 Innsbruck (Austria)

2008-09-15

200

Valence-Rydberg Bonding in Bimolecular R-Ca+ Anthony E. Ketvirtis and Jack Simons*  

E-print Network

were performed on species associated with the bimolecular reaction of protonated methylamine (CH3NH3 before exothermic dissociation; on inclusion of zero-point vibrational energy, this barrier disappears),4c (NH4)2 + fragmentation is endothermic to all dissociation products.4a,b,9 For this reason

Simons, Jack

201

Unusual structure, bonding and properties in a californium borate.  

PubMed

The participation of the valence orbitals of actinides in bonding has been debated for decades. Recent experimental and computational investigations demonstrated the involvement of 6p, 6d and/or 5f orbitals in bonding. However, structural and spectroscopic data, as well as theory, indicate a decrease in covalency across the actinide series, and the evidence points to highly ionic, lanthanide-like bonding for late actinides. Here we show that chemical differentiation between californium and lanthanides can be achieved by using ligands that are both highly polarizable and substantially rearrange on complexation. A ligand that suits both of these desired properties is polyborate. We demonstrate that the 5f, 6d and 7p orbitals are all involved in bonding in a Cf(III) borate, and that large crystal-field effects are present. Synthetic, structural and spectroscopic data are complemented by quantum mechanical calculations to support these observations. PMID:24755589

Polinski, Matthew J; Garner, Edward B; Maurice, Rémi; Planas, Nora; Stritzinger, Jared T; Parker, T Gannon; Cross, Justin N; Green, Thomas D; Alekseev, Evgeny V; Van Cleve, Shelley M; Depmeier, Wulf; Gagliardi, Laura; Shatruk, Michael; Knappenberger, Kenneth L; Liu, Guokui; Skanthakumar, S; Soderholm, Lynda; Dixon, David A; Albrecht-Schmitt, Thomas E

2014-05-01

202

Unusual structure, bonding and properties in a californium borate  

NASA Astrophysics Data System (ADS)

The participation of the valence orbitals of actinides in bonding has been debated for decades. Recent experimental and computational investigations demonstrated the involvement of 6p, 6d and/or 5f orbitals in bonding. However, structural and spectroscopic data, as well as theory, indicate a decrease in covalency across the actinide series, and the evidence points to highly ionic, lanthanide-like bonding for late actinides. Here we show that chemical differentiation between californium and lanthanides can be achieved by using ligands that are both highly polarizable and substantially rearrange on complexation. A ligand that suits both of these desired properties is polyborate. We demonstrate that the 5f, 6d and 7p orbitals are all involved in bonding in a Cf(III) borate, and that large crystal-field effects are present. Synthetic, structural and spectroscopic data are complemented by quantum mechanical calculations to support these observations.

Polinski, Matthew J.; Garner, Edward B.; Maurice, Rémi; Planas, Nora; Stritzinger, Jared T.; Parker, T. Gannon; Cross, Justin N.; Green, Thomas D.; Alekseev, Evgeny V.; van Cleve, Shelley M.; Depmeier, Wulf; Gagliardi, Laura; Shatruk, Michael; Knappenberger, Kenneth L.; Liu, Guokui; Skanthakumar, S.; Soderholm, Lynda; Dixon, David A.; Albrecht-Schmitt, Thomas E.

2014-05-01

203

Syllabus CHEM 4311/CHEM 8833 1. Structure and Models of Bonding  

E-print Network

Syllabus CHEM 4311/CHEM 8833 1. Structure and Models of Bonding · Atomic structure · Quantum numbers and atomic orbitals · Lewis structures · Valence-shell electron pair repulsion rules in electronic structure theory · Larger molecules: Qualitative molecular orbital theory (QMOT) First Exam 2

Houston, Paul L.

204

Bond University Queensland, Australia  

E-print Network

Bond University Queensland, Australia About: Bond University is a private university located institutions, Bond has a strong component of international students who hail from some 80 countries worldwide. Bond's small size, internationalized-student body, 14-week trimesters, and fabulous Gold Coast location

Duchowski, Andrew T.

205

Savings Bonds Value Calculator  

NSDL National Science Digital Library

From the Federal Reserve Bank of New York, this site computes the redemption value of users's US savings bonds. Easy-to-use pull-down menus allow visitors to enter information such as the date of issue and face value of their Series E bonds, Series EE bonds, and Series S bonds. After entering the information, the Calculator will then show a chart of issue dates and denominations and actual worth of the bonds, if cashed within a set period of time.

206

Cobalt lawsone complexes: searching for new valence tautomers.  

PubMed

Bi-stable molecular systems presenting valence tautomerism are associated with the development of new functional materials, which can be used for applications in organic electric conductors, optoelectronic and molecular magnetic devices. The properties of these materials can be adjusted with slight chemical changes and can be induced by external stimuli. Typical examples of valence tautomer compounds are coordination complexes of Co and o-dioxolene ligands, notably quinone like ones. In the search for a new class of cobalt complexes presenting valence tautomerism we report herein the synthesis and characterization of five new coordination compounds of cobalt and 2-hydroxy-1,4-naphthoquinone (lawsone or shortly Law). Complexes [Co(Law)2(im)2]·C6H5CH3 (1), [Co(Law)2(py)2]·CH3OH (2), [Co(Law)2(phen)]·(C4H8O)2 (3), [Co(Law)2(2,2-bpy)]·C6H5CH3 (4) and [Co(Law)2(2,2-bpy)] (5) were synthesized and fully characterized by X-ray diffraction and EPR techniques in a wide range of temperatures and under illumination. Despite presenting similar molecular and geometry packing of the valence tautomer complexes of cobalt and o-dioxolenes, neither structural nor electronic evidence of valence tautomerism could be found in the Co and lawsone complexes. PMID:23423385

Ribeiro, Marcos A; Lanznaster, Maurício; Silva, Marcos M P; Resende, Jackson A L C; Pinheiro, Maurício V B; Krambrock, Klaus; Stumpf, Humberto O; Pinheiro, Carlos B

2013-04-21

207

Optical study of archetypical valence-fluctuating Eu systems.  

PubMed

We have investigated the optical conductivity of the prominent valence-fluctuating compounds EuIr(2)Si(2) and EuNi(2)P(2) in the infrared energy range to get new insights into the electronic properties of valence-fluctuating systems. For both compounds, we observe upon cooling the formation of a renormalized Drude response, a partial suppression of the optical conductivity below 100 meV, and the appearance of a midinfrared peak at 0.15 eV for EuIr(2)Si(2) and 0.13 eV for EuNi(2)P(2). Most remarkably, our results show a strong similarity with the optical spectra reported for many Ce- or Yb-based heavy-fermion metals and intermediate valence systems, although the phase diagrams and the temperature dependence of the valence differ strongly between Eu systems and Ce- or Yb-based systems. This suggests that the hybridization between 4f and conduction electrons, which is responsible for the properties of Ce and Yb systems, plays an important role in valence-fluctuating Eu systems. PMID:23368375

Guritanu, V; Seiro, S; Sichelschmidt, J; Caroca-Canales, N; Iizuka, T; Kimura, S; Geibel, C; Steglich, F

2012-12-14

208

Investing in Bonds.com  

NSDL National Science Digital Library

Investing in Bonds was created by the Bond Market Association to educate investors about the benefits of bonds investing. The Investor's Guide to Bond Basics educates investors about the types of bonds available, criteria for evaluating a bond, a guide to buying bonds, bond investment strategies and a glossary of bond market terms. The Bond Market section provides an overview of the U.S. bond market while the Investor's Checklist section takes the investor step-by-step through the bond investment decision process. Investors will also find sections with information on municipal bonds, corporate bonds, mortgage securities and U.S. Inflation-Indexed Securities.

209

LET'S BOND! A Chemical Bonding Webquest  

NSDL National Science Digital Library

Today we are going to use the internet to explore chemical bonding! Even though there are just a few questions for each website, you need to read the entire content. Don't worry about understanding all of it, but make sure that you are familiar with it! Stay on task and have fun! Let's start with some basics. Click on the link below and answer the questions on your worksheet under "Bonding Basics". Bonding Basics Good job! Lets move on and talk about ions. Ions are a big part of bonding, so make sure you get this section down pat! Click on the ...

Hicken, Mrs.

2009-04-08

210

Kernel density estimation applied to bond length, bond angle, and torsion angle distributions.  

PubMed

We describe the method of kernel density estimation (KDE) and apply it to molecular structure data. KDE is a quite general nonparametric statistical method suitable even for multimodal data. The method generates smooth probability density function (PDF) representations and finds application in diverse fields such as signal processing and econometrics. KDE appears to have been under-utilized as a method in molecular geometry analysis, chemo-informatics, and molecular structure optimization. The resulting probability densities have advantages over histograms and, importantly, are also suitable for gradient-based optimization. To illustrate KDE, we describe its application to chemical bond length, bond valence angle, and torsion angle distributions and show the ability of the method to model arbitrary torsion angle distributions. PMID:24746022

McCabe, Patrick; Korb, Oliver; Cole, Jason

2014-05-27

211

Unconventional Quantum Criticality Due to Critical Valence Transition  

NASA Astrophysics Data System (ADS)

Quantum criticality due to the valence transition in some Yb-based heavy fermion metals has gradually turned out to play a crucial role to understand the non-Fermi liquid properties that cannot be understood from the conventional quantum criticality theory due to magnetic transitions. Namely, critical exponents giving the temperature (T) dependence of the resistivity ?(T), the Sommerfeld coefficient, C(T)/T, the magnetic susceptibility, ?(T), and the NMR relaxation rates, 1/(T1T), can be understood as the effect of the critical valence fluctuations of f electrons in Yb ion in a unified way. There also exist a series of Ce-based heavy fermion metals that exhibit anomalies in physical quantities, enhancements of the residual resistivity ?0 and the superconducting critical temperature (Tc) around the pressure where the valence of Ce sharply changes. Here we review the present status of these problems both from experimental and theoretical aspects.

Miyake, Kazumasa; Watanabe, Shinji

2014-06-01

212

Hydroxide-catalyzed bonding  

NASA Technical Reports Server (NTRS)

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

Gwo, Dz-Hung (Inventor)

2003-01-01

213

From mixed valence to the Kondo lattice regime  

NASA Astrophysics Data System (ADS)

Many heavy fermion materials are known to cross over from the Kondo lattice regime to the mixed valence regime or vice versa as a function of pressure or doping. We study this crossover theoretically by employing the periodic Anderson model within the framework of the dynamical mean field theory. Changes occurring in the dynamics and transport across this crossover are highlighted. As the valence is decreased (increased) relative to the Kondo lattice regime, the Kondo resonance broadens significantly, while the lower (upper) Hubbard band moves closer to the Fermi level. The resistivity develops a two peak structure in the mixed valence regime: a low temperature coherence peak and a high temperature ‘Hubbard band’ peak. These two peaks merge, yielding a broad shallow maximum upon decreasing the valence further. The optical conductivity likewise exhibits an unusual absorption feature (shoulder) in the deep mid-infrared region, which grows in intensity with decreasing valence. The involvement of the Hubbard bands in dc transport and of the effective f-level in the optical conductivity are shown to be responsible for the anomalous transport properties. A two-band hybridization-gap model, which neglects incoherent effects due to many-body scattering, commonly employed to understand the optical response in these materials is shown to be inadequate, especially in the mixed valence regime. Comparison of theory with experiment carried out for (a) dc resistivities of CeRhIn5, Ce2Ni3Si5, CeFeGe3 and YbIr2Si2, (b) pressure dependent resistivity of YbInAu2 and CeCu6, and (c) optical conductivity measurements in YbIr2Si2 yields excellent agreement.

Kumar, Pramod; Vidhyadhiraja, N. S.

2011-12-01

214

From mixed valence to the Kondo lattice regime.  

PubMed

Many heavy fermion materials are known to cross over from the Kondo lattice regime to the mixed valence regime or vice versa as a function of pressure or doping. We study this crossover theoretically by employing the periodic Anderson model within the framework of the dynamical mean field theory. Changes occurring in the dynamics and transport across this crossover are highlighted. As the valence is decreased (increased) relative to the Kondo lattice regime, the Kondo resonance broadens significantly, while the lower (upper) Hubbard band moves closer to the Fermi level. The resistivity develops a two peak structure in the mixed valence regime: a low temperature coherence peak and a high temperature 'Hubbard band' peak. These two peaks merge, yielding a broad shallow maximum upon decreasing the valence further. The optical conductivity likewise exhibits an unusual absorption feature (shoulder) in the deep mid-infrared region, which grows in intensity with decreasing valence. The involvement of the Hubbard bands in dc transport and of the effective f-level in the optical conductivity are shown to be responsible for the anomalous transport properties. A two-band hybridization-gap model, which neglects incoherent effects due to many-body scattering, commonly employed to understand the optical response in these materials is shown to be inadequate, especially in the mixed valence regime. Comparison of theory with experiment carried out for (a) dc resistivities of CeRhIn(5), Ce(2)Ni(3)Si(5), CeFeGe(3) and YbIr(2)Si(2), (b) pressure dependent resistivity of YbInAu(2) and CeCu(6), and (c) optical conductivity measurements in YbIr(2)Si(2) yields excellent agreement. PMID:22080675

Kumar, Pramod; Vidhyadhiraja, N S

2011-12-01

215

High valence 3p and transition metal based MOFs.  

PubMed

This article focuses on high valence 3p and transition metal based metal organic frameworks. In the first part we will discuss the complex solution chemistry of these metals which makes this sub-class of MOFs more of a challenge than the traditional low valence metal based MOFs. This is followed by a short review of the different classes of solids based on phosphonates, carboxylates and other linkers. Finally, we report some of the most relevant properties of these solids such as their chemical or thermal stability as well as their catalytic, redox- and photo-activities. PMID:24947910

Devic, Thomas; Serre, Christian

2014-08-21

216

Channel Bonding Notes 03/25/2004 Channel Bonding Notes  

E-print Network

Channel Bonding Notes 03/25/2004 Channel Bonding Notes Luke Hindman Department of Computer Science by attempting to use the Linux kernel bonding driver (bonding.o) to implement channel bonding on the master node. However, each time I would bring up the bonded interface (bond0) I would loose communication

Jain, Amit

217

Superatomic orbitals in sixteen-coordinate M@Li16 bonded by metallic bonds  

NASA Astrophysics Data System (ADS)

Based on density-functional calculation and genetic algorithm structure search, we propose a series of 16-coordinate core-shell clusters: M@Li16(M = Ca, Sr, Ba, Ti, Zr, Hf). A tetrahedral (Td) structure with an outer shell of 16 lithium atoms and one enclosed heavy atom is found to be the global minimum in the structural exploration of BaLi16 based on genetic algorithm. This structure also has lower energy compared to the other isomers we employed in all the MLi16 clusters. In this structure, the atoms are bonded together by metallic bonds with alkali (IA) and alkaline-earth (IIA) metal atoms. Their corresponding first electronic shells are closed with significant energy gaps because their total numbers of valence electrons fulfil the 18-electron rule. Such a combination could be extended to 20-electron systems by enclosing IVB elements. With simple valence electrons and highly symmetric structures, superatomic molecular orbitals are identified in all of the Td clusters.

Gu, Xiao; Chen, Guo-Hong; Ji, Min; Yao, Yong-Xin; Gong, Xin-Gao

2012-03-01

218

The Bond Market Association  

NSDL National Science Digital Library

The Bond Market Association "represents securities firms and banks that underwrite, trade and sell debt securities." Their web site is divided into several sections. The Research Desk presents the results of research conducted by the association, including forecasts of economic growth and analysis of bond market trends. The Legislative Issues and Regulatory sections provide a summary of legislative and regulatory developments of interest to the bond market community. Market Practices contains guidelines and procedures to be followed in the bond market. The site also provides information to investors on how to invest in corporate bonds, tax-exempt municipal bonds, and mortgage securities.

219

NMR studies of ordered structures and valence states in the successive valence-transition system EuPtP  

NASA Astrophysics Data System (ADS)

We have studied EuPtP, which undergoes two successive valence transitions at TA˜240 K and TB˜200 K by 31P-nuclear magnetic resonance (NMR) measurements. From the analysis of NMR spectra, we obtained plausible ordered structures and Eu valence states in three phases divided by TA and TB. These ordered structures well explain observed inequivalent P sites and the intensity ratio of the NMR spectra arising from these P sites. The results are also in good accordance with mean Eu valence measured by the x-ray absorption spectroscopy. We also discuss Eu 4 f states and the origin of the transitions from the measurements of nuclear spin lattice relaxation rate and hyperfine coupling constant.

Mito, T.; Nishitani, K.; Koyama, T.; Muta, H.; Maruyama, T.; Pristáš, G.; Ueda, K.; Kohara, T.; Mitsuda, A.; Sugishima, M.; Wada, H.

2014-11-01

220

Essays on corporate bonds  

E-print Network

This thesis consists of three empirical essays on corporate bonds, examining the role of both credit risk and liquidity. In the first chapter, I test the ability of structural models of default to price corporate bonds in ...

Bao, Jack (Jack C.)

2009-01-01

221

Paradigms and Plastic Facts in the History of Valence.  

ERIC Educational Resources Information Center

Traces the development of bonding theory and notes the influence of preconceived theory upon this development. Considers ideas of alchemy, Newton, Dalton, Lewis, and quantum mechanics. Suggests a move away from conservative descriptive approaches of bonding theory. (ML)

Zavaleta, David

1988-01-01

222

Relativistic effects on the electronic structure and chemical bonding of UF6  

NASA Astrophysics Data System (ADS)

We have studied the relativistic effects in the electronic structure and chemical bonding for the ground state of UF6, using the relativistic and nonrelativistic discrete-variational X? molecular orbital calculations. It is found that two relativistic effects appear in the valence levels; the energy level splitting and upward shift of energies of the molecular orbitals. From the Mulliken population analysis of the valence levels, it is shown that the level splitting is due to mixing of the uranium atomic orbitals with a strong spin-orbit interaction, such as U6p, and the upward shift due to the increase in the screening of the nuclear charge and charge redistribution. The strength of U-F bonding remarkably increases for the relativistic case, because the changes in the radial distributions due to the relativistic effects induce both the decrease in the antibonding interactions and the increase in the bonding ones.

Onoe, Jun; Takeuchi, Kazuo; Nakamatsu, Hirohide; Mukoyama, Takeshi; Sekine, Rika; Kim, Bong-Il; Adachi, Hirohiko

1993-11-01

223

Bonding silicones with epoxies  

SciTech Connect

It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

Tira, J.S.

1980-01-01

224

Approximate treatments of intermediate valence and heavy fermion model systems  

Microsoft Academic Search

The development and applications of approximations for the electronic properties of intermediate valence and heavy fermion systems within the last six years is reviewed. The most part of the paper deals with the single impurity and the lattice version of the Anderson model of magnetic moments within a metal. The methods described from a unifying point of view are mean-field

G. Czycholl

1986-01-01

225

Mobile linkers on DNA-coated colloids: valency without patches  

E-print Network

Colloids coated with single-stranded DNA (ssDNA) can bind selectively to other colloids coated with complementary ssDNA. The fact that DNA-coated colloids (DNACCs) can bind to specific partners opens the prospect of making colloidal `molecules'. However, in order to design DNACC-based molecules, we must be able to control the valency of the colloids, i.e. the number of partners to which a given DNACC can bind. One obvious, but not very simple approach is to decorate the colloidal surface with patches of single-stranded DNA that selectively bind those on other colloids. Here we propose a design principle that exploits many-body effects to control the valency of otherwise isotropic colloids. Using a combination of theory and simulation, we show that we can tune the valency of colloids coated with mobile ssDNA, simply by tuning the non-specific repulsion between the particles. Our simulations show that the resulting effective interactions lead to low-valency colloids self-assembling in peculiar open structures, very different from those observed in DNACCs with immobile DNA linkers.

Stefano Angioletti-Uberti; Patrick Varilly; Bortolo M. Mognetti; Daan Frenkel

2014-08-27

226

Real-time observation of valence electron motion.  

SciTech Connect

The superposition of quantum states drives motion on the atomic and subatomic scales, with the energy spacing of the states dictating the speed of the motion. In the case of electrons residing in the outer (valence) shells of atoms and molecules which are separated by electronvolt energies, this means that valence electron motion occurs on a subfemtosecond to few-femtosecond timescale (1 fs = 10{sup -15} s). In the absence of complete measurements, the motion can be characterized in terms of a complex quantity, the density matrix. Here we report an attosecond pump-probe measurement of the density matrix of valence electrons in atomic krypton ions. We generate the ions with a controlled few-cycle laser field and then probe them through the spectrally resolved absorption of an attosecond extreme-ultraviolet pulse, which allows us to observe in real time the subfemtosecond motion of valence electrons over a multifemtosecond time span. We are able to completely characterize the quantum mechanical electron motion and determine its degree of coherence in the specimen of the ensemble. Although the present study uses a simple, prototypical open system, attosecond transient absorption spectroscopy should be applicable to molecules and solid-state materials to reveal the elementary electron motions that control physical, chemical and biological properties and processes.

Goulielmakis, E.; Loh, Z.-H.; Wirth, A.; Santra, R.; Rohringer, N.; Yakovlev, V. S.; Zherebtsov, S.; Pfeifer, T.; Azzeer, A. M.; Kling, M. F.; Leone, S. R.; Krausz, F.; Chemical Sciences and Engineering Division; Max-Planck-Insti. fur Quantenoptik; Univ. of California at Berkeley; LBNL; Univ. of Chicago; LLNL; Ludwig-Maximilians-Univ.; King Saud Univ.

2010-08-05

227

The Magnetic Interaction of a Valence Electron with Inner Shells  

Microsoft Academic Search

The magnetic interaction terms between two electrons are well known. By using antisymmetric wave functions the diagonal terms of the energy matrix for this interaction are calculated for an electronic configuration consisting of a valence electron and a closed shell. From the diagonal elements the doublet separation is easily obtained by applying the energy sum rule. The direct integrals, that

M. H. Johnson; G. Breit

1933-01-01

228

Recognizing the Emotional Valence of Names: An ERP Study  

ERIC Educational Resources Information Center

Unlike common nouns, person names refer to unique entities and generally have a referring function. We used event-related potentials to investigate the time course of identifying the emotional meaning of nouns and names. The emotional valence of names and nouns were manipulated separately. The results show early N1 effects in response to emotional…

Wang, Lin; Zhu, Zude; Bastiaansen, Marcel; Hagoort, Peter; Yang, Yufang

2013-01-01

229

Vection Modulates Emotional Valence of Autobiographical Episodic Memories  

ERIC Educational Resources Information Center

We examined whether illusory self-motion perception ("vection") induced by viewing upward and downward grating motion stimuli can alter the emotional valence of recollected autobiographical episodic memories. We found that participants recollected positive episodes more often while perceiving upward vection. However, when we tested a small moving…

Seno, Takeharu; Kawabe, Takahiro; Ito, Hiroyuki; Sunaga, Shoji

2013-01-01

230

Valence state at the surface of rare-earth metals  

Microsoft Academic Search

The valence state of a rare-earth metal surface is investigated by using general properties of the surface tension of metals. Thereby it is concluded that samarium is likely to have a divalent or partly divalent surface on top of its trivalent bulk phase, which agrees with recent spectroscopic observations. Also californium metal is discussed from this point of view. Finally,

Börje Johansson

1979-01-01

231

Two-electron bond-orbital model, 2  

NASA Technical Reports Server (NTRS)

The two-electron bond-orbital model of tetrahedrally-coordinated solids is generalized and its application extended. All intrabond matrix elements entering the formalism are explicitly retained, including the direct overlap S between the anion and cation sp3 hybrid wavefunctions. Complete analytic results are obtained for the six two-electron eigenvalues and eigenstates of the anion-cation bond in terms of S, one-electron parameters V2 and V3, and two-electron correlation parameters V4, V5 and V6. Refined formulas for the dielectric constant and the nuclear exchange and pseudodipolar coefficients, as well as new expressions for the valence electron density, polarity of the bond and the cohesive energy, are then derived. The theory gives a good account of the experimentally observed trends in all properties considered and approximate quantitative agreement is achieved for the pseudodipolar coefficient.

Huang, C.; Moriarty, J. A.; Sher, A.

1976-01-01

232

Spin-assisted covalent bond mechanism in ``charge-ordering'' perovskite oxides  

NASA Astrophysics Data System (ADS)

First-principles density functional calculations on the metal-insulator transition (MIT) in perovskite CaFeO3 point to local ferromagnetic coupling as the microscopic origin for the electronic “charge order” transition. Our atomic, electronic, and magnetic structure analyses reveal that the MIT results from a spin-assisted covalent bonding mechanism between the O 2p and Fe 3d states with anisotropic Fe-O bonds and negligible intersite Fe-Fe charge transfer. We suggest that control of the lattice distortions, which mediate the covalent bond formation, in oxides containing late transition-metal row cations in high valence states provides a platform to tailor electronic transitions.

Cammarata, Antonio; Rondinelli, James M.

2012-11-01

233

Effects of lattice strain and ion displacement on the bonding mechanism of the ferroelectric perovskite material BaTiO3: first-principles study  

Microsoft Academic Search

The effects of lattice strain and ion displacement on the bonding mechanism of the perovskite material BaTiO3 have been studied by using the density-functional theory within the full-potential linear augmented plane wave (FP-LAPW) method. The valence and the bonding charge density, the density of states (DOS), the local DOS and the partial DOS were calculated to investigate the bonding mechanisms.

H B Shu; G C Zhou; X L Zhong; L Z Sun; J B Wang; X S Chen; Y C Zhou

2007-01-01

234

Rapid adhesive bonding concepts  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

235

Local Currency Bond Markets  

Microsoft Academic Search

This paper analyzes the development of 49 local bond markets. The main finding is that policies and laws matter: countries with stable inflation rates and strong creditor rights have more developed local bond markets and rely less on foreign- currency-denominated bonds. The results suggest that \\

FRANCIS E. WARNOCK

2006-01-01

236

Acrylic mechanical bond tests  

SciTech Connect

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

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

1991-02-01

237

Superatom-atom super-bonding in metallic clusters: a new look to the mystery of an Au20 pyramid.  

PubMed

Using the super valence bond model, a generalized chemical picture for the electronic shells of an Au20 pyramid is given. It is found that Au20 can be viewed to be a superatomic molecule, of which its superatomic 16c-16e core (T) is in D(3)S hybridization bonded with four vertical Au atoms for the molecule-like (TAu4) electronic shell-closure. Based on such a superatom-atom bonding model, TX4 (X = F, Cl, or Br) are predicted to be very stable. Such a superatom-atom T-Au/T-X bonding enriches the scope of chemistry. PMID:25259476

Cheng, Longjiu; Zhang, Xiuzhen; Jin, Baokang; Yang, Jinlong

2014-11-01

238

Prospective bonding applications  

NASA Astrophysics Data System (ADS)

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

Ancenay, H.; Benazet, D.

1981-07-01

239

Bonding thermoplastic polymers  

DOEpatents

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

Wallow, Thomas I. (Fremont, CA); Hunter, Marion C. (Livermore, CA); Krafcik, Karen Lee (Livermore, CA); Morales, Alfredo M. (Livermore, CA); Simmons, Blake A. (San Francisco, CA); Domeier, Linda A. (Danville, CA)

2008-06-24

240

Snake venom disintegrins: novel dimeric disintegrins and structural diversification by disulphide bond engineering.  

PubMed

We report the isolation and amino acid sequences of six novel dimeric disintegrins from the venoms of Vipera lebetina obtusa (VLO), V. berus (VB), V. ammodytes (VA), Echis ocellatus (EO) and Echis multisquamatus (EMS). Disintegrins VLO4, VB7, VA6 and EO4 displayed the RGD motif and inhibited the adhesion of K562 cells, expressing the integrin alpha5beta1 to immobilized fibronectin. A second group of dimeric disintegrins (VLO5 and EO5) had MLD and VGD motifs in their subunits and blocked the adhesion of the alpha4beta1 integrin to vascular cell adhesion molecule 1 with high selectivity. On the other hand, disintegrin EMS11 inhibited both alpha5beta1 and alpha4beta1 integrins with almost the same degree of specificity. Comparison of the amino acid sequences of the dimeric disintegrins with those of other disintegrins by multiple-sequence alignment and phylogenetic analysis, in conjunction with current biochemical and genetic data, supports the view that the different disintegrin subfamilies evolved from a common ADAM (a disintegrin and metalloproteinase-like) scaffold and that structural diversification occurred through disulphide bond engineering. PMID:12667142

Calvete, Juan J; Moreno-Murciano, M Paz; Theakston, R David G; Kisiel, Dariusz G; Marcinkiewicz, Cezary

2003-06-15

241

Work Valence as a Predictor of Academic Achievement in the Family Context  

ERIC Educational Resources Information Center

This study asserts a theoretical model of academic and work socialization within the family setting. The presumed associations between parents' work valences, children's work valences and valence perceptions, and children's academic interest and achievement are tested. The results suggest that children's perceptions of parents…

Porfeli, Erik; Ferrari, Lea; Nota, Laura

2013-01-01

242

Valence admixture in the EuxRh1-x amorphous alloys  

NASA Astrophysics Data System (ADS)

Magnetic, Mössbauer, and LIII-edge measurements are reported on the EuxRh1-x amorphous alloys. The experimental results clearly indicate that an inhomogeneous valence admixture occurs in the disordered phase. The fluctuating valence encountered in the crystalline EuRh2 is destroyed by the structural disorder. The average valence is discussed in terms of local environment.

Malterre, D.; Menny, A.; Delcroix, P.; Durand, J.; Krill, G.; Marchal, G.

1989-05-01

243

Electron delocalization in mixed-valence Keggin polyoxometalates. Ab initio calculation of the local e ective  

E-print Network

Electron delocalization in mixed-valence Keggin polyoxometalates. Ab initio calculation-valence polyoxometalates reduced by two electrons. For that purpose, we extract from valence-spectroscopy ab initio in polyoxometalates. Finally, these parameters are introduced in an extended Hubbard hamiltonian that models the whole

244

Developmental Reversals in False Memory: Effects of Emotional Valence and Arousal  

ERIC Educational Resources Information Center

Do the emotional valence and arousal of events distort children's memories? Do valence and arousal modulate counterintuitive age increases in false memory? We investigated those questions in children, adolescents, and adults using the Cornell/Cortland Emotion Lists, a word list pool that induces false memories and in which valence and arousal can…

Brainerd, C. J.; Holliday, R. E.; Reyna, V. F.; Yang, Y.; Toglia, M. P.

2010-01-01

245

How are hydrogen bonds modified by metal binding?  

PubMed

We have used density functional theory calculations to investigate how the hydrogen-bond strength is modified when a ligand is bound to a metal using over 60 model systems involving six metals and eight ligands frequently encountered in metalloproteins. We study how the hydrogen-bond geometry and energy vary with the nature of metal, the oxidation state, the coordination number, the ligand involved in the hydrogen bond, other first-sphere ligands, and different hydrogen-bond probe molecules. The results show that, in general, the hydrogen-bond strength is increased for neutral ligands and decreased for negatively charged ligands. The size of the effect is mainly determined by the net charge of the metal complex, and all effects are typically decreased when the model is solvated. In water solution, the hydrogen-bond strength can increase by up to 37 kJ/mol for neutral ligands, and that of negatively charged ligands can increase (for complexes with a negative net charge) or decrease (for positively charged complexes). If the net charge of the complex does not change, there is normally little difference between different metals or different types of complexes. The only exception is observed for sulphur-containing ligands (Met and Cys) and if the ligand is redox-active (e.g. high-valence Fe-O complexes). PMID:23543233

Husberg, Charlotte; Ryde, Ulf

2013-06-01

246

Spin effects in activation of hydrocarbons  

Microsoft Academic Search

A simple valence bond (VB) method is used in order to stress the role of triplet excited state of hydrocarbons in spin-uncoupling mechanism of their activation by transition metal center. The nature of activation barriers in bimolecular reactions is determined by exchange repulsion between closed shell molecules; a catalyst can diminish the barrier assisting the change of spin-coupling schemes in

Boris F. Minaev

2001-01-01

247

Prediction of the bond lengths, vibrational frequencies, and bond dissociation energy of octahedral seaborgium hexacarbonyl, Sg(CO){sub 6}  

SciTech Connect

The recent syntheses of several new elements (including the recent reports of elements 116 and 118), coupled with the controversy surrounding the naming of elements 104--109, have stimulated a great interest in the chemistry of the transactinide elements. This contribution addresses hypothetical hexacarbonyl complex of seaborgium (Sg, element 106), which is predicted to be a 6d-block transition element with six valence electrons, analogous to Cr, Mo, and W. The authors have previously predicted that, if it were to exist, Sg(CO){sub 6} would exhibit metal-carbonyl bonding that is very similar to that in Cr(CO){sub 6}, Mo(CO){sub 6}, and W(CO){sub 6}, and quite unlike that of the unknown valence isoelectronic actinide complex U(CO){sub 6}. This finding is in accord with the scant experimental data available for Sg. The relativistic DV-X{alpha} method used in the earlier paper facilitated the analysis of the molecular orbitals of Sg(CO){sub 6}, but did not allow for the calculation of total-energy properties, such as bond lengths and vibrational frequencies. Here the authors will use the superior methodology they have applied to other transactinide molecules to compare the bond lengths, vibrational frequencies, and CO dissociation energy of hypothetical Sg(CO){sub 6} to those of Mo(CO){sub 6} and W(CO){sub 6}.

Nash, C.S.; Bursten, B.E.

1999-11-24

248

Theoretical calculations of valence states in Fe-Mo compounds  

NASA Astrophysics Data System (ADS)

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.

Estrada, F.; Noverola, H.; Suárez, J. R.; Navarro, O.; Avignon, M.

2014-04-01

249

Bonded semiconductor substrate  

DOEpatents

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

Atwater, Jr.; Harry A. (South Pasadena, CA), Zahler; James M. (Pasadena, CA)

2010-07-13

250

Color Magnetic Corrections to Quark Model Valence Distributions  

E-print Network

We calculate order $\\alpha_s$ color magnetic corrections to the valence quark distributions of the proton using the Los Alamos Model Potential wavefunctions. The spin-spin interaction breaks the model SU(4) symmetry, providing a natural mechanism for the difference between the up and down distributions. For a value of $\\alpha_s$ sufficient to produce the $N-\\Delta$ mass splitting, we find up and down quark distributions in reasonable agreement with experiment.

Benesh, C J

1993-01-01

251

Valence holes observed in nanodiamonds dispersed in water.  

PubMed

Colloidal dispersion is essential for most nanodiamond applications, but its influence on nanodiamond electronic properties remains unknown. Here we have probed the electronic structure of oxidized detonation nanodiamonds dispersed in water by using soft X-ray absorption and emission spectroscopies at the carbon and oxygen K edges. Upon dispersion in water, the ?* transitions from sp(2)-hybridized carbon disappear, and holes in the valence band are observed. PMID:25597533

Petit, Tristan; Pflüger, Mika; Tolksdorf, Daniel; Xiao, Jie; Aziz, Emad F

2015-02-01

252

Chemical bonding technology  

NASA Technical Reports Server (NTRS)

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

Plueddemann, E.

1986-01-01

253

Energy pulse bonding  

NASA Technical Reports Server (NTRS)

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

Smith, G. C.

1972-01-01

254

A local view of bonding and diffusion at metal surfaces  

SciTech Connect

First-principles density functional calculations and corresponding experimental results underline the importance of basic chemical concepts, such as coordination, valence saturation and promotion-hybridization energetics, in understanding bonding and diffusion of atoms at and on metal surfaces. Several examples are reviewed, including outer-layer relaxations of clean hcp(0001) surfaces, liquid-metal-embrittlement energetics, separation energies of metal-adatom dimers, concerted substitutional self-diffusion on fcc(001) surfaces, and adsorption and diffusion barrier sites for adatoms near steps.

Feibelman, P.J.

1996-09-01

255

Sketching the pion's valence-quark generalised parton distribution  

E-print Network

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...

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

2014-01-01

256

Core-core and core-valence correlation  

NASA Technical Reports Server (NTRS)

The effect of (1s) core correlation on properties and energy separations was analyzed using full configuration-interaction (FCI) calculations. The Be 1 S - 1 P, the C 3 P - 5 S and CH+ 1 Sigma + or - 1 Pi separations, and CH+ spectroscopic constants, dipole moment and 1 Sigma + - 1 Pi transition dipole moment were studied. The results of the FCI calculations are compared to those obtained using approximate methods. In addition, the generation of atomic natural orbital (ANO) basis sets, as a method for contracting a primitive basis set for both valence and core correlation, is discussed. When both core-core and core-valence correlation are included in the calculation, no suitable truncated CI approach consistently reproduces the FCI, and contraction of the basis set is very difficult. If the (nearly constant) core-core correlation is eliminated, and only the core-valence correlation is included, CASSCF/MRCI approached reproduce the FCI results and basis set contraction is significantly easier.

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

1988-01-01

257

Basic features of the pion valence-quark distribution function  

NASA Astrophysics Data System (ADS)

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?(x); namely, at a characteristic hadronic scale, q?(x)?(1 for x?0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum.

Chang, Lei; Mezrag, Cédric; Moutarde, Hervé; Roberts, Craig D.; Rodríguez-Quintero, Jose; Tandy, Peter C.

2014-10-01

258

Valency configuration of transition metal impurities in ZnO  

SciTech Connect

We use the self-interaction corrected local spin-density approximation to investigate the ground state valency configuration of transition metal (TM=Mn, Co) impurities in n- and p-type ZnO. We find that in pure Zn{sub 1-x}TM{sub x}O, the localized TM{sup 2+} configuration is energetically favored over the itinerant d-electron configuration of the local spin density (LSD) picture. Our calculations indicate furthermore that the (+/0) donor level is situated in the ZnO gap. Consequently, for n-type conditions, with the Fermi energy {epsilon}F close to the conduction band minimum, TM remains in the 2+ charge state, while for p-type conditions, with {epsilon}F close to the valence band maximum, the 3+ charge state is energetically preferred. In the latter scenario, modeled here by co-doping with N, the additional delocalized d-electron charge transfers into the entire states at the top of the valence band, and hole carriers will only exist, if the N concentration exceeds the TM impurity concentration.

Petit, Leon [ORNL; Schulthess, Thomas C [ORNL; Svane, Axel [University of Aarhus, Denmark; Temmerman, Walter M [Daresbury Laboratory, UK; Szotek, Zdzislawa [Daresbury Laboratory, UK; Janotti, Anderson [University of California, Santa Barbara

2006-01-01

259

Interchannel coupling effects in the valence photoionization of SF6.  

PubMed

The complex Kohn and polyatomic Schwinger variational techniques have been employed to illustrate the interchannel coupling correlation effects in the valence photoionization dynamics of SF6. Partial photoionization cross sections and asymmetry parameters of six valence subshells (1t1g, 5t1u, 1t2u, 3eg, 1t2g, 4t1u) are discussed in the framework of several theoretical and experimental studies. The complex Kohn results are in rather good agreement with experimental results, indicative of the fact that the interchannel coupling effects alter the photoionization dynamics significantly. We find that the dominant effect of interchannel coupling is to reduce the magnitude of shape resonant cross sections near the threshold and to induce resonant features in other channels to which resonances are coupled. The long-standing issue concerning ordering of the valence orbitals is addressed and confirmed 4t1u (6)1t2g (6)3eg (4)(5t1u (6)+1t2u (6)) 1t1g (6) as the most likely ordering. PMID:24880278

Jose, J; Lucchese, R R; Rescigno, T N

2014-05-28

260

Teachers' Domain: Covalent Bonding  

NSDL National Science Digital Library

This Flash interactive tutorial explores covalent bonding, a type of chemical bond that involves sharing of electrons. Learners investigate the attractive and repulsive forces that act on atomic particles and how the sharing of electrons can keep atoms together. See how two hydrogen atoms interact with each other to create a covalent bond. Learn about patterns in the periodic table and how electrostatic potential energy determines the bond length. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-16

261

Hydrogen bonding and anaesthesia  

NASA Astrophysics Data System (ADS)

General anaesthetics act by perturbing intermolecular associations without breaking or forming covalent bonds. These associations might be due to a variety of van der Waals interactions or hydrogen bonding. Neurotransmitters all contain OH or NH groups, which are prone to form hydrogen bonds with those of the neurotransmitter receptors. These could be perturbed by anaesthetics. Aromatic rings in amino acids can act as weak hydrogen bond acceptors. On the other hand the acidic hydrogen in halothane type anaesthetics are weak proton donors. These two facts together lead to a probable mechanism of action for all general anaesthetics.

Sándorfy, C.

2004-12-01

262

Valenced Cues and Contexts Have Different Effects on Event-Based Prospective Memory  

PubMed Central

This study examined the separate influence and joint influences on event-based prospective memory task performance due to the valence of cues and the valence of contexts. We manipulated the valence of cues and contexts with pictures from the International Affective Picture System. The participants, undergraduate students, showed higher performance when neutral compared to valenced pictures were used for cueing prospective memory. In addition, neutral pictures were more effective as cues when they occurred in a valenced context than in the context of neutral pictures, but the effectiveness of valenced cues did not vary across contexts that differed in valence. The finding of an interaction between cue and context valence indicates that their respective influence on event-based prospective memory task performance cannot be understood in isolation from each other. Our findings are not consistent with by the prevailing view which holds that the scope of attention is broadened and narrowed, respectively, by positively and negatively valenced stimuli. Instead, our findings are more supportive of the recent proposal that the scope of attention is determined by the motivational intensity associated with valenced stimuli. Consistent with this proposal, we speculate that the motivational intensity associated with different retrieval cues determines the scope of attention, that contexts with different valence values determine participants’ task engagement, and that prospective memory task performance is determined jointly by attention scope and task engagement. PMID:25647484

Graf, Peter; Yu, Martin

2015-01-01

263

Role of valence fluctuations in the superconductivity of Ce122 compounds.  

PubMed

Pressure dependence of the Ce valence in CeCu(2)Ge(2) has been measured up to 24 GPa at 300 K and to 17 GPa at 18-20 K using x-ray absorption spectroscopy in the partial fluorescence yield. A smooth increase of the Ce valence with pressure is observed across the two superconducting (SC) regions without any noticeable irregularity. The chemical pressure dependence of the Ce valence was also measured in Ce(Cu(1-x)Ni(x))(2)Si(2) at 20 K. A very weak, monotonic increase of the valence with x was observed, without any significant change in the two SC regions. Within experimental uncertainties, our results show no evidence for the valence transition with an abrupt change in the valence state near the SC II region, challenging the valence-fluctuation mediated superconductivity model in these compounds at high pressure and low temperature. PMID:25192112

Yamaoka, H; Ikeda, Y; Jarrige, I; Tsujii, N; Zekko, Y; Yamamoto, Y; Mizuki, J; Lin, J-F; Hiraoka, N; Ishii, H; Tsuei, K-D; Kobayashi, T C; Honda, F; Onuki, Y

2014-08-22

264

Role of Valence Fluctuations in the Superconductivity of Ce122 Compounds  

NASA Astrophysics Data System (ADS)

Pressure dependence of the Ce valence in CeCu2Ge2 has been measured up to 24 GPa at 300 K and to 17 GPa at 18-20 K using x-ray absorption spectroscopy in the partial fluorescence yield. A smooth increase of the Ce valence with pressure is observed across the two superconducting (SC) regions without any noticeable irregularity. The chemical pressure dependence of the Ce valence was also measured in Ce(Cu1-xNix)2Si2 at 20 K. A very weak, monotonic increase of the valence with x was observed, without any significant change in the two SC regions. Within experimental uncertainties, our results show no evidence for the valence transition with an abrupt change in the valence state near the SC II region, challenging the valence-fluctuation mediated superconductivity model in these compounds at high pressure and low temperature.

Yamaoka, H.; Ikeda, Y.; Jarrige, I.; Tsujii, N.; Zekko, Y.; Yamamoto, Y.; Mizuki, J.; Lin, J.-F.; Hiraoka, N.; Ishii, H.; Tsuei, K.-D.; Kobayashi, T. C.; Honda, F.; ?nuki, Y.

2014-08-01

265

30 CFR 57.22227 - Approved testing devices (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2014 CFR

...II-A, II-B, III, IV, V-A, and V-B mines). 57.22227 Section 57.22227 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2014-07-01

266

30 CFR 57.22227 - Approved testing devices (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2012 CFR

...II-A, II-B, III, IV, V-A, and V-B mines). 57.22227 Section 57.22227 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

267

30 CFR 57.22201 - Mechanical ventilation (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2012 CFR

...II-A, II-B, III, IV, V-A, and V-B mines). 57.22201 Section 57.22201 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

268

30 CFR 57.22201 - Mechanical ventilation (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2013 CFR

...II-A, II-B, III, IV, V-A, and V-B mines). 57.22201 Section 57.22201 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

269

30 CFR 57.22201 - Mechanical ventilation (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2014 CFR

...II-A, II-B, III, IV, V-A, and V-B mines). 57.22201 Section 57.22201 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2014-07-01

270

30 CFR 57.22227 - Approved testing devices (I-A, I-B, I-C, II-A, II-B, III, IV, V-A, and V-B mines).  

Code of Federal Regulations, 2013 CFR

...II-A, II-B, III, IV, V-A, and V-B mines). 57.22227 Section 57.22227 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

271

Interfacial bonding stability  

NASA Technical Reports Server (NTRS)

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

Boerio, J.

1984-01-01

272

The dissociative bond.  

PubMed

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

Gordon, Nirit

2013-01-01

273

Visionlearning: Chemical Bonding  

NSDL National Science Digital Library

This digital learning module provides an easily-understood overview of chemical bonding for users with little formal background in chemistry or physics. It explores ionic bonding through the example of sodium (an alkali metal) reacting with chlorine gas to produce common table salt. A concept simulation further illustrates the process.

Carpi, Anthony

2011-07-12

274

The Sibling Bond.  

ERIC Educational Resources Information Center

The relationships among brothers and sisters are infinitely varied, but whatever their characteristics, these bonds last throughout life. This book examines the sibling relationship as a distinctive emotional, passionate, painful, and solacing power. Chapter 1, "Unraveling the Sibling Bond," addresses research on siblings and development of the…

Bank, Stephen P.; Kahn, Michael D.

275

Interactive Pi Bonding Effects  

NSDL National Science Digital Library

This application demonstrates the effect of pi bonding on the one-electron ligand field splitting in an octahedral. By clicking on the appropriate buttons students can see how D changes when you move from ligands with no pi bonding capability to pi donor and pi acceptor ligands.

276

Wood Bond Testing  

NASA Technical Reports Server (NTRS)

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

1989-01-01

277

Shape Bonding method  

NASA Technical Reports Server (NTRS)

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

Pontius, James T. (Inventor)

2010-01-01

278

The bonding of simple carboxylic acids on Cu(110)  

NASA Astrophysics Data System (ADS)

We present a study of the bonding of formate (HCOO) and acetate (CH3COO) chemisorbed on Cu(110) using core level spectroscopies in combination with theoretical calculations. For the first time, we apply x-ray emission spectroscopy (XES) to these systems. When XES is used in conjunction with x-ray absorption spectroscopy (XAS) and ab initio calculations, new information about the electronic interaction in the adsorbate-substrate system is provided. In particular, we have used the azimuthal orientation of the COO-surface bond on the (110) surface, to make a complete partition into x, y, and z orbital contributions. The surface bond is found to be predominantly ionic. For the case of adsorbed formate, the covalent bonding is dominated by 6a1/7a1, (?)-type, frontier orbitals, interacting with the Cu valence band. The resulting hybrid orbitals form a distribution of states that cross the Fermi level. The contribution from adsorbate ?-type orbitals is small. The chemical bond formation of adsorbed acetate is very similar to that of formate. In addition, states with metal character have been identified for the outermost CH3-group of acetate. These are delocalized states of mainly local ?-character. The spectral features due to states of local ?-character in the adsorbed acetate are well described within the framework of hyperconjugation.

Karis, O.; Hasselström, J.; Wassdahl, N.; Weinelt, M.; Nilsson, A.; Nyberg, M.; Pettersson, L. G. M.; Stöhr, J.; Samant, M. G.

2000-05-01

279

Mixed-valence state of symmetric diruthenium complexes: synthesis, characterization, and electron transfer investigation.  

PubMed

Complexes of the type {[(pyS)Ru(NH(3))(4)](2)-?-L}(n), where pyS = 4-mercaptopyridine, L = 4,4'-dithiodipyridine (pySSpy), pyrazine (pz) and 1,4-dicyanobenzene (DCB), and n = +4 and +5 for fully reduced and mixed-valence complexes, respectively, were synthesized and characterized. Electrochemical data showed that there is electron communication between the metal centers with comproportionation constants of 33.2, 1.30 × 10(8) and 5.56 × 10(5) for L = pySSpy, pz and DCB, respectively. It was also observed that the electronic coupling between the metal centers is affected by the ?-back-bonding interaction toward the pyS ligand. Raman spectroscopy showed a dependence of the intensity of the vibrational modes on the exciting radiations giving support to the assignments of the electronic transitions. The degree of electron communication between the metal centers through the bridging ligands suggests that these systems can be molecular wire materials. PMID:23086129

Pinheiro, Solange de Oliveira; Paulo, Tércio de F; de Abreu, Dieric dos S; Longhinotti, Elisane; Silva, Claudio H B; Andrade, Gustavo F S; Temperini, Márcia L A; Diógenes, Izaura Cirino Nogueira

2012-12-28

280

Crystal structure of a mixed-valence ?-oxide Sn12 cluster.  

PubMed

The mixed-valence ?-oxide Sn12 cluster, deca-carbonyl-tetra-?4-oxido-hexa-?3-oxido-tetra-kis-[?-2,2'-(pyridine-2,6-di-yl)bis(1,1-di-phenyl-ethano-lato)]deca-tin(II)ditin(IV)dimolyb-denum(O)(2 Mo-Sn) toluene hepta-solvate, [Mo2Sn12(C33H27NO2)4O10(CO)10]·7C7H8, has a crystallographically imposed inversion centre. The asymmetric unit also contains three and a half toluene solvent mol-ecules, one of which is disordered about a centre of symmetry. The complex mol-ecule comprises six distinct Sn atom species with four different coordination numbers, namely 3, 4, 5, and 6. The Sn(II) atoms forming the central Sn10O10 core adopt distorted trigonal-pyramidal, square-pyramidal and octa-hedral coordination geometries provided by the ?-oxide atoms and by the O- and N-donor atoms of two pyridinedi-ethano-late ligands. The terminal Sn(IV) atoms have distorted trigonal-bipyramidal coordination geometries, with a ?4-oxide atom and the N atom of a pyridinedi-ethano-late ligand occupying the axial positions, and the Mo atom of a Mo(CO)5 group and the alk-oxy O atoms of a ligand forming the equatorial plane. In the crystal, weak intra- and inter-molecular C-H?O hydrogen bonds are observed. PMID:25484784

Kireenko, Marina M; Zaitsev, Kirill V; Karlov, Sergey S; Egorov, Mikhail P; Churakov, Andrei V

2014-11-01

281

Beryllium dimer: a bond based on non-dynamical correlation.  

PubMed

The bond nature in beryllium dimer has been theoretically investigated using high-level ab initio methods. A series of ANO basis sets of increasing quality, going from sp to spdf ghi contractions, has been employed, combined with HF, CAS-SCF, CISD, and MRCI calculations with several different active spaces. The quality of these calculations has been checked by comparing the results with valence Full-CI calculations, performed with the same basis sets. It is shown that two quasi-degenerated partly occupied orbitals play a crucial role to give a qualitatively correct description of the bond. Their nature is similar to that of the edge orbitals that give rise to the quasi-degenerated singlet-triplet states in longer beryllium chains. PMID:24866399

El Khatib, Muammar; Bendazzoli, Gian Luigi; Evangelisti, Stefano; Helal, Wissam; Leininger, Thierry; Tenti, Lorenzo; Angeli, Celestino

2014-08-21

282

The law of constant rejection. [chemical bonding in crystals  

NASA Technical Reports Server (NTRS)

Improvements in analytical technique, study of multielement partitioning in natural systems, and improvements in ionic radius values have permitted construction of Onuma diagrams, in which the logarithm of partition coefficient is plotted versus ionic radius. The optimum radii, corresponding to crystallographic sites, do change in response to changes in major element composition for any particular mineral-type. In natural systems elements compete for sites rather than substituting for another element. It is proposed on empirical grounds, for equilibrium ionic bonding, that Onuma diagram curves for a particular lattice site are parabolic near optimum radius, linear elsewhere, parallel for different valences, and mirror images on opposite sides of optimum. Deviations may be due to overlapping peaks, liquid structure, polyvalence, bonding differences, contamination, kinetics, alteration, etc. However, dominant crystal-chemical control is indicated.

Philpotts, J. A.

1978-01-01

283

Nucleon and pion distribution functions in the valence region  

NASA Astrophysics Data System (ADS)

An experimental and theoretical perspective is provided on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain, namely, Bjorken x?0.4 . This domain is a key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. The focus is on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the standard model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, an explanation that an upgraded Jefferson Laboratory facility is well suited to provide new data on the nucleon is provided, while a future electron-ion collider could provide essential new data for the mesons. There is also great potential in using Drell-Yan interactions, at FNAL, CERN, J-PARC, and GSI, to push into the large- x domain for both mesons and nucleons. Furthermore, it is argued that explanation, in contrast to modeling and parametrization, requires a widespread acceptance of the need to adapt theory: to the lessons learnt already from the methods of nonperturbative quantum-field theory and a fuller exploitation of those methods.

Holt, Roy J.; Roberts, Craig D.

2010-10-01

284

Kissing bonds A kissing bond is adhesively bonded but holds little of the strength usually  

E-print Network

Kissing bonds · A kissing bond is adhesively bonded but holds little of the strength usually weight saving and excellent stress transfer. · The ability to reliably assess defects in adhesive bonds · To develop a non destructive method to assess the integrity of adhesive bonds using pulsed phase thermography

Sóbester, András

285

Control of bond-strain-induced electronic phase transitions in iron perovskites.  

PubMed

Unusual electronic phase transitions in the A-site ordered perovskites LnCu3Fe4O12 (Ln: trivalent lanthanide ion) are investigated. All LnCu3Fe4O12 compounds are in identical valence states of Ln(3+)Cu(2+)3Fe(3.75+)4O12 at high temperature. LnCu3Fe4O12 with larger Ln ions (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb) show an intersite charge transfer transition (3Cu(2+) + 4Fe(3.75+) ? 3Cu(3+) + 4Fe(3+)) in which the transition temperature decreases from 360 to 240 K with decreasing Ln ion size. In contrast, LnCu3Fe4O12 with smaller Ln ions (Ln = Dy, Ho, Er, Tm Yb, Lu) transform into a charge-disproportionated (8Fe(3.75+) ? 5Fe(3+) + 3Fe(5+)) and charge-ordered phase below ?250-260 K. The former series exhibits metal-to-insulator, antiferromagnetic, and isostructural volume expansion transitions simultaneously with intersite charge transfer. The latter shows metal-to-semiconductor, ferrimagnetic, and structural phase transitions simultaneously with charge disproportionation. Bond valence calculation reveals that the metal-oxygen bond strains in these compounds are classified into two types: overbonding or compression stress (underbonding or tensile stress) in the Ln-O (Fe-O) bond is dominant in the former series, while the opposite stresses or bond strains are found in the latter. Intersite charge transfer transition temperatures are strongly dependent upon the global instability indices that represent the structural instability calculated from the bond valence sum, whereas the charge disproportionation occurs at almost identical temperatures, regardless of the magnitude of structural instability. These findings provide a new aspect of the structure-property relationship in transition metal oxides and enable precise control of electronic states by bond strains. PMID:24224928

Yamada, Ikuya; Etani, Hidenobu; Tsuchida, Kazuki; Marukawa, Shohei; Hayashi, Naoaki; Kawakami, Takateru; Mizumaki, Masaichiro; Ohgushi, Kenya; Kusano, Yoshihiro; Kim, Jungeun; Tsuji, Naruki; Takahashi, Ryoji; Nishiyama, Norimasa; Inoue, Toru; Irifune, Tetsuo; Takano, Mikio

2013-12-01

286

Pion and kaon valence-quark parton distribution functions.  

SciTech Connect

A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.

Nguyen, T.; Bashir, A.; Roberts, C. D.; Tandy, P. C. (Physics); (Kent State Univ.); (Univ. Michoacana de San Nicolas de Hidalgo); (Kavli Inst. for Theoretical Physics China); (Peking Univ.)

2011-06-16

287

Pion and kaon valence-quark parton distribution functions  

SciTech Connect

A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.

Nguyen, Trang [Center for Nuclear Research, Department of Physics, Kent State University, Kent, Ohio 44242 (United States); Bashir, Adnan [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Michoacan 58040 (Mexico); Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); Roberts, Craig D. [Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Physics, Center for High Energy Physics and the State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Tandy, Peter C. [Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China)

2011-06-15

288

Wafer-Level Thermocompression Bonds  

E-print Network

Thermocompression bonding of gold is a promising technique for achieving low temperature, wafer-level bonding without the application of an electric field or complicated pre-bond cleaning procedure. The presence of a ductile ...

Tsau, Christine H.

289

Intermolecular hydrogen bond energies in crystals evaluated using electron density properties: DFT computations with periodic boundary conditions.  

PubMed

The hydrogen bond (H-bond) energies are evaluated for 18 molecular crystals with 28 moderate and strong O-H···O bonds using the approaches based on the electron density properties, which are derived from the B3LYP/6-311G** calculations with periodic boundary conditions. The approaches considered explore linear relationships between the local electronic kinetic G(b) and potential V(b) densities at the H···O bond critical point and the H-bond energy E(HB). Comparison of the computed E(HB) values with the experimental data and enthalpies evaluated using the empirical correlation of spectral and thermodynamic parameters (Iogansen, Spectrochim. Acta Part A 1999, 55, 1585) enables to estimate the accuracy and applicability limits of the approaches used. The V(b)-E(HB) approach overestimates the energy of moderate H-bonds (E(HB) < 60 kJ/mol) by ~20% and gives unreliably high energies for crystals with strong H-bonds. On the other hand, the G(b)-E(HB) approach affords reliable results for the crystals under consideration. The linear relationship between G(b) and E(HB) is basis set superposition error (BSSE) free and allows to estimate the H-bond energy without computing it by means of the supramolecular approach. Therefore, for the evaluation of H-bond energies in molecular crystals, the G(b) value can be recommended to be obtained from both density functional theory (DFT) computations with periodic boundary conditions and precise X-ray diffraction experiments. PMID:22786749

Vener, M V; Egorova, A N; Churakov, A V; Tsirelson, V G

2012-11-01

290

Junk-Bond Colleges.  

ERIC Educational Resources Information Center

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

Van Der Werf, Martin

2003-01-01

291

Gold Thermocompression Wafer Bonding  

E-print Network

Thermocompression bonding of gold is a promising technique for the fabrication and packaging microelectronic and MEMS devices. The use of a gold interlayer and moderate temperatures and pressures results in a hermetic, ...

Spearing, S. Mark

292

+2 Valence Metal Concentrations in Lion Creek, Oakland, California  

NASA Astrophysics Data System (ADS)

Seven major creeks exist within the City of Oakland, California. These creeks all flow in the southwest direction from forested hills down through densely populated streets where they become susceptible to urban runoff. Lion Creek has been diverted to engineered channels and underground culverts and runs directly under our school (Roots International) before flowing into the San Leandro Bay. One branch of the creek begins near an abandoned sulfur mine. Previous studies have shown that extremely high levels of lead, arsenic and iron exist in this portion of the creek due to acid mine drainage. In this study +2 valence heavy metals concentration data was obtained from samples collected from a segment of the creek located approximately 2.8 miles downstream from the mine. Concentrations in samples collected at three different sites along this segment ranged between 50 ppb and 100 ppb. We hypothesize that these levels are related to the high concentration of +2 valence heavy metals at the mining site. To test this hypothesis, we have obtained samples from various locations along the roughly 3.75 miles of Lion Creek that are used to assess changes in heavy metals concentration levels from the mining site to the San Leandro Bay.

Vazquez, P.; Zedd, T.; Chagolla, R.; Dutton-Starbuck, M.; Negrete, A.; Jinham, M.; Lapota, M.

2012-12-01

293

Ligand-hole localization in oxides with unusual valence Fe  

PubMed Central

Unusual high-valence states of iron are stabilized in a few oxides. A-site-ordered perovskite-structure oxides contain such iron cations and exhibit distinct electronic behaviors at low temperatures, e.g. charge disproportionation (4Fe4+ ? 2Fe3+ + 2Fe5+) in CaCu3Fe4O12 and intersite charge transfer (3Cu2+ + 4Fe3.75+ ? 3Cu3+ + 4Fe3+) in LaCu3Fe4O12. Here we report the synthesis of solid solutions of CaCu3Fe4O12 and LaCu3Fe4O12 and explain how the instabilities of their unusual valence states of iron are relieved. Although these behaviors look completely different from each other in simple ionic models, they can both be explained by the localization of ligand holes, which are produced by the strong hybridization of iron d and oxygen p orbitals in oxides. The localization behavior in the charge disproportionation of CaCu3Fe4O12 is regarded as charge ordering of the ligand holes, and that in the intersite charge transfer of LaCu3Fe4O12 is regarded as a Mott transition of the ligand holes. PMID:22690318

Chen, Wei-Tin; Saito, Takashi; Hayashi, Naoaki; Takano, Mikio; Shimakawa, Yuichi

2012-01-01

294

Intracranial markers of emotional valence processing and judgments in music.  

PubMed

The involvement of the amygdala and orbitofrontal cortex in the processing of valenced stimuli is well established. However, less is known about the extent to which activity in these regions reflects a stimulus' physical properties, the individual subjective experience it evokes, or both. We recorded cortical electrical activity from five epileptic patients implanted with depth electrodes for presurgical evaluation while they rated "consonant" and "dissonant" musical chords using a "pleasantness" scale. We compared the pattern of responses in the amygdala and orbitofrontal cortex when trials were sorted by pleasantness judgments relative to when they were sorted by the acoustic properties known to influence emotional reactions to musical chords. This revealed earlier differential activity in the amygdala in the physical properties-based, relative to in the judgment-based, analyses. Thus, our results demonstrate that the amygdala has, first and foremost, a high initial sensitivity to the physical properties of valenced stimuli. The finding that differentiations in the amygdala based on pleasantness ratings had a longer latency suggests that in this structure, mediation of emotional judgment follows accumulation of sensory information. This is in contrast to the orbitofrontal cortex where sensitivity to sensory information did not precede differentiation based on affective judgments. PMID:25496511

Omigie, Diana; Dellacherie, Delphine; Hasboun, Dominique; Clément, Sylvain; Baulac, Michel; Adam, Claude; Samson, Séverine

2015-03-01

295

Energetics and thermodynamic stability of the mixed valence ytterbium germanides.  

PubMed

The results of an experimental study concerning the thermodynamic stability of the Yb germanides, described as intermediate valence compounds, complemented by a computational investigation for the Yb3Ge5 compound are reported. These compounds belong to the rare earth (RE) tetrelides (tetrel = Si, Ge, i.e., group 14 elements), a class of intermetallic materials showing unusual and promising physical properties (giant magnetocaloric effect, magnetostriction, and magnetoresistence). The high-temperature decomposition reactions of the Yb-Ge intermediate phases were studied experimentally by means of the KEMS (Knudsen effusion mass spectrometry) and KEWL (Knudsen effusion weight loss) techniques. From the reaction enthalpies derived by measuring the Yb(g) decomposition pressures as a function of temperature, the heats of formation of five out of six of the intermediate phases in the Yb-Ge system were calculated. From the computational side, the stability of the Yb3Ge5(s) compound has been investigated by DFT-LCAO-B3LYP (density functional theory-linear combination of atomic orbitals-hybrid b3lyp exchange-correlation functional) first principles calculations deriving its equilibrium geometry and the enthalpy of formation at 0 K in relation to the intermediate valence state of Yb in the lattice. PMID:17444673

Balducci, G; Brutti, S; Ciccioli, A; Gigli, G; Palenzona, A; Pani, M

2007-05-17

296

An ecological valence theory of human color preference  

PubMed Central

Color preference is an important aspect of visual experience, but little is known about why people in general like some colors more than others. Previous research suggested explanations based on biological adaptations [Hurlbert AC, Ling YL (2007) Curr Biol 17:623–625] and color-emotions [Ou L-C, Luo MR, Woodcock A, Wright A (2004) Color Res Appl 29:381–389]. In this article we articulate an ecological valence theory in which color preferences arise from people’s average affective responses to color-associated objects. An empirical test provides strong support for this theory: People like colors strongly associated with objects they like (e.g., blues with clear skies and clean water) and dislike colors strongly associated with objects they dislike (e.g., browns with feces and rotten food). Relative to alternative theories, the ecological valence theory both fits the data better (even with fewer free parameters) and provides a more plausible, comprehensive causal explanation of color preferences. PMID:20421475

Palmer, Stephen E.; Schloss, Karen B.

2010-01-01

297

Water's Hydrogen Bond Strength  

E-print Network

Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperatures. The overall conclusion of this investigation is that water's hydrogen bond strength is poised centrally within a narrow window of its suitability for life.

Martin Chaplin

2007-06-10

298

Structural evolution and valence electron-state change during ultra thin silicon-oxide growth  

NASA Astrophysics Data System (ADS)

We have studied valence electron-state changes of Si during initial oxidation of Si(111) clean surface, HF-treated Si(001) and Si(111) surfaces by Auger valence electron spectroscopy (AVES). The results showed that the valence electron-state changes during initial oxidation were sensitively reflected in Si[2s,2p,V] (V=3s,3p) AVES spectra and that they depended on both initial surface treatment and surface orientation. The local valence electron-states, local density of states in other words, showed the characteristic-structure evolution depending on the initial surface treatment and surface orientation.

Shimizu, A.; Abe, S.; Nakayama, H.; Nishino, T.; Iida, S.

2000-06-01

299

Fair Scheduling on Parallel Bonded Channels with Intersecting Bonding Groups  

E-print Network

Fair Scheduling on Parallel Bonded Channels with Intersecting Bonding Groups Gongbing Hong, James for providing weighted sharing of aggregate capacity in networks having parallel bonded channels in which a single channel may simultaneously be a member of multiple bonding groups. Our work is motivated

Martin, Jim

300

30 CFR 581.33 - Bonds and bonding requirements.  

Code of Federal Regulations, 2013 CFR

...Resources 2 2013-07-01 2013-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 581.33 Bonds and bonding requirements. (a) When the leasing notice...

2013-07-01

301

Leave with Pay Bond/Waiver of Bond Form  

E-print Network

Leave with Pay Bond/Waiver of Bond Form Submit to: The Office of Faculty Affairs and Professional Development, ADM 451 I. As you were granted a leave with pay, you must either post a bond in the amount of the salary to be paid during the leave or be granted a waiver of the bond. Most faculty members request

302

30 CFR 281.33 - Bonds and bonding requirements.  

Code of Federal Regulations, 2011 CFR

...Resources 2 2011-07-01 2011-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 281.33 Bonds and bonding requirements. (a) When the leasing notice...

2011-07-01

303

30 CFR 581.33 - Bonds and bonding requirements.  

Code of Federal Regulations, 2014 CFR

...Resources 2 2014-07-01 2014-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 581.33 Bonds and bonding requirements. (a) When the leasing notice...

2014-07-01

304

30 CFR 581.33 - Bonds and bonding requirements.  

Code of Federal Regulations, 2012 CFR

...Resources 2 2012-07-01 2012-07-01 false Bonds and bonding requirements. 581.33 Section 581.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 581.33 Bonds and bonding requirements. (a) When the leasing notice...

2012-07-01

305

30 CFR 281.33 - Bonds and bonding requirements.  

Code of Federal Regulations, 2010 CFR

...Resources 2 2010-07-01 2010-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations § 281.33 Bonds and bonding requirements. (a) When the leasing notice...

2010-07-01

306

Thio- and selenoglycosides as ligands for biomedically relevant lectins: Valency-activity correlations for benzene-based dithiogalactoside clusters and first assessment for (di)selenodigalactosides.  

PubMed

Substitution of the oxygen atom in the glycosidic linkage by a disulfide bond or by selenium makes the resulting glycoside resistant to hydrolysis. To clarify the consequences for affinity to lectins we prepared benzene-based mono- to trivalent dithiogalactosides. Inhibitory capacity increased with valency for a plant toxin, the synthetic compounds potently blocking its binding to a lactose-presenting matrix and to cells. Human galectins were much less sensitive to the disulfides than the toxin. This differential response constitutes a beneficial effect to avoid cross-reactivity in vivo. Symmetrical selenodigalactoside and diselenodigalactoside were prepared and similarly tested. Both compounds proved rather equally bioactive for the toxin, graded activity was measured for human galectins. This result directs attention to further studies to relate Se-dependent alterations in bond angle and length as well as van der Waals radius to binding properties of selenoglycosides to biomedically relevant lectins. PMID:25599835

André, Sabine; Kövér, Katalin E; Gabius, Hans-Joachim; Szilágyi, László

2015-02-15

307

Formation of unprecedented actinidecarbon triple bonds in uranium methylidyne molecules  

PubMed Central

Chemistry of the actinide elements represents a challenging yet vital scientific frontier. Development of actinide chemistry requires fundamental understanding of the relative roles of actinide valence-region orbitals and the nature of their chemical bonding. We report here an experimental and theoretical investigation of the uranium methylidyne molecules X3UCH (X = F, Cl, Br), F2ClUCH, and F3UCF formed through reactions of laser-ablated uranium atoms and trihalomethanes or carbon tetrafluoride in excess argon. By using matrix infrared spectroscopy and relativistic quantum chemistry calculations, we have shown that these actinide complexes possess relatively strong UC triple bonds between the U 6d-5f hybrid orbitals and carbon 2s-2p orbitals. Electron-withdrawing ligands are critical in stabilizing the U(VI) oxidation state and sustaining the formation of uranium multiple bonds. These unique UC-bearing molecules are examples of the long-sought actinide-alkylidynes. This discovery opens the door to the rational synthesis of triple-bonded actinidecarbon compounds. PMID:18024591

Lyon, Jonathan T.; Hu, Han-Shi; Andrews, Lester; Li, Jun

2007-01-01

308

Bond Markets with Stochastic Volatility  

E-print Network

Bond Markets with Stochastic Volatility Rafael DeSantiago Jean-Pierre Fouque Knut Sølna September 27, 2007 Abstract We analyze stochastic volatility effects in the context of the bond market- nection to defaultable bonds. Contents 1 Introduction 2 2 Pricing Bonds 3 2.1 The Term Structure Equation

Solna, Knut

309

Mössbauer spectroscopic study on valence-detrapping and trapping of mixed-valence trinuclear iron(III, III, II) fluorine-substituted benzoate complexes  

NASA Astrophysics Data System (ADS)

Four mixed-valence trinuclear iron(III, III, II) fluorine-substituted benzoate complexes were synthesized; Fe3O(C6F5COO)6(C5H5N)3·CH2Cl2 ( 1), Fe3O(C6F5COO)6(C5H5N)3 ( 2), Fe3O(2H-C6F4COO)6(C5H5N)3 ( 3), and Fe3O(4H-C6F4COO)6(C5H5N)3 ( 4), in which valence-detrapping and trapping phenomena have been investigated by 57Fe- Mössbauer spectroscopy. The valence state of the three iron ions is trapped at lower temperatures while it is fully detrapped at higher temperatures for 1. Valence detrapping is not observed for 2, 3, and 4 even at room temperature, although Mössbauer spectra for 3 and 4 show complicated temperature dependence.

Sakai, Yoichi; Onaka, Satoru; Takahashi, Masashi; Ogiso, Ryo; Takayama, Tsutomu; Nakamoto, Tadahiro

2012-03-01

310

Surface analysis in composite bonding  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

311

Shear bond strength of four orthodontic bonding systems.  

PubMed

Recently new orthodontic bonding systems have been developed for attachment of brackets to the etched facial surfaces of teeth. Two of these new systems use bonding agents that contain solvents. It is claimed that this improves the polymerization of the unfilled resin primer and may increase bond strength. A new light-cured restorative enamel/dentin-bonding agent has also recently been introduced. Its value in orthodontic bonding has not been determined. The aim of this investigation was to evaluate the shear bond strengths of the three new bonding systems and to compare these with a conventional orthodontic bonding system. Forty-eight enamel specimens were prepared with 600-grit silicone carbide paper, acid etched with 37% phosphoric acid, and assigned to four enamel-bonding treatment groups: (A) Saga sealant; (B) Maximum Cure; (C) Scotchbond-2; and (D) Concise enamel bond. After enamel priming, the specimens were bonded to Concise orthodontic bonding resin. The bonded specimens were thermocycled (15 degrees C to 45 degrees C) and then stored in distilled water at 37 degrees C for 7 days. Shear bond strength was tested with an Instron testing machine at a strain rate of 0.02 in/min. The mean shear bond strengths and standard deviations reported in MN/m2 were (A) 20.34 (5.37); (B) 25.33 (5.96); (C) 14.59 (5.25); and (D) 20.13 (4.98). The mean shear bond strengths for groups A, B, and D were significantly greater (p less than 0.05) than that for group C. The addition of solvents to the new orthodontic bonding systems does not appear to have a clinically significant effect. The new restorative bonding resin does not provide comparable enamel bond strengths. PMID:2405634

Coreil, M N; McInnes-Ledoux, P; Ledoux, W R; Weinberg, R

1990-02-01

312

Prediction of initial emission rates of 2-butoxyethanol from consumer products using equilibrium headspace concentrations: an application of the vapor pressure and boundary layer (VB) model.  

PubMed

The initial emission rate of volatile organic compounds (VOCs) from consumer products is important for assessing potential human exposure to VOCs in products. The vapor pressure and boundary layer (VB) model developed in the past was used to predict the emission rates of VOCs in the fast decaying phase from petroleum-based wet materials. This study has extended the model to largely water-based products. Study results have shown a good agreement (ratio = 1.01, r2 = 0.89) between model-predicted initial emission rates (ER0) of 2-butoxyethanol (2-BE) based on its equilibrium headspace concentration and experimentally measured ER0 in a small dynamic environmental chamber for 20 consumer products. These water-based products included wood surface treating stains, general cleaning agents, and degreasers with 2-BE concentrations over a wide range. The results also demonstrated a dependency between the headspace concentrations of the target analytes and the water content in the liquid. But dependency on water content had no effect on the use of headspace concentration to predict the ER0. The ER0 of 2-BE in the products ranged from 100 to 3000 mg m(-2) h(-1). In the majority of cases, the 2-BE concentration range in individual products indicated in the Material Safety Data Sheet agreed with the measured data. PMID:16294857

Zhu, Jiping; Li, Henrik; Korchinski, Mark; Fellin, Phil

2005-11-01

313

Comparison of brain capillary endothelial cell-based and epithelial (MDCK-MDR1, Caco-2, and VB-Caco-2) cell-based surrogate blood-brain barrier penetration models.  

PubMed

An accurate means of predicting blood-brain barrier (BBB) penetration and blood-brain partitioning of NCEs (new chemical entities) would fulfill a major need in pharmaceutical research. Currently, an industry-standard BBB drug penetration model is not available. Primary brain capillary endothelial cells, optionally co-cultured with astrocytes and/or pericytes, are the most valued models of BBB. For routine use, establishing and maintaining a co-culture system is too costly and labor intensive. Alternatively, non-cerebral cell lines such as MDCK-MDR1 are used, and most recently, the suitability of native and modified Caco-2 for predicting brain penetration has also come under investigation. This study provides comparative data on the morphology and functionality of the high integrity brain capillary endothelial BBB model (EPA: triple culture of brain capillary endothelial cells with pericytes and astrocytes) and the epithelial cell-based (native Caco-2, high P-glycoprotein expressing vinblastine-treated VB-Caco-2 and MDCK-MDR1) surrogate BBB models. Using a panel of 10 compounds VB-Caco-2 and MDCK-MDR1 cell lines show restrictive paracellular pathway and BBB-like selective passive permeability that makes them comparable to the rat brain BBB model, which gave correlation with the highest r(2) value with in vivo permeability data. In bidirectional assay, the VB-Caco-2 and the MDCK-MDR1 models identified more P-glycoprotein drug substrates than the rat brain BBB model. While the complexity and predictive value of the BBB model is the highest, for the screening of NCEs to determine whether they are efflux substrates or not, the VB-Caco-2 and the MDCK-MDR1 models may provide a simple and inexpensive tool. PMID:22906709

Hellinger, Eva; Veszelka, Szilvia; Tóth, Andrea E; Walter, Fruzsina; Kittel, Agnes; Bakk, Mónika Laura; Tihanyi, Károly; Háda, Viktor; Nakagawa, Shinsuke; Duy, Thuy Dinh Ha; Niwa, Masami; Deli, Mária A; Vastag, Monika

2012-10-01

314

The computation of C-C and N-N bond dissociation energies for singly, doubly, and triply bonded systems  

NASA Technical Reports Server (NTRS)

The bond dissociation energies (De) of C2H2, C2H4, C2H6, N2, N2H2, and N2H4 are studied at various levels of correlation treatment. The convergence of De with respect to the one-particle basis is studied at the single-reference modified coupled-pair-functional (MCPF)level. At all levels of correlation treatment, the errors in the bond dissociation energies increase with the degree of multiple bond character. The multireference configuration-interaction (MRCI) De values, corrected for an estimate of higher excitations, are in excellent agreement with those determined using the size-extensive averaged-coupled-pair-functional (ACPF) method. The full-valence complete-active-space self-consistent-field (CASSCF)/MRCI calculations are reproduced very well by MRCI calculations based on a CASSCF calculation that includes in the active space only those electrons involved in the C-C or N-N bonds.

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

1991-01-01

315

Molecular orbital (SCF-X??-SW) theory of metal-metal charge transfer processes in minerals - I. application to Fe2+???Fe3+ charge transfer and "electron delocalization" in mixed-valence iron oxides and silicates  

USGS Publications Warehouse

A number of mixed valence iron oxides and silicates (e.g., magnetite, ilvaite) exhibit thermally induced electron delocalization between adjacent Fe2+ and Fe3+ ions and optically induced electronic transitions which are assigned to Fe2+???Fe3+ intervalence charge transfer. In this paper, the mechanism of electron delocalization (i.e., polarons versus itinerant electrons) and the nature of optically induced intervalence charge-transfer in minerals are investigated using molecular orbital theory. SCF-X??-SW molecular orbital calculations were done for several mixed-valence (Fe2O10)15- clusters corresponding to edgesharing Fe2+ and Fe3+ coordination polyhedra. A spinunrestricted formalism was used so that the effect of ferromagnetic versus antiferromagnetic coupling of adjacent Fe2+ and Fe3+ cations could be determined. The molecular orbital results can be related to the polaron theory of solid state physics and the perturbation theory formalism used by Robin and Day (1967) and others to describe electron transfer in mixed valence compounds. Intervalence charge-transfer results from the overlap of Fe(3d) orbitals across the shared edges of adjacent FeO6 polyhedra to give weak Fe-Fe bonds. Electron delocalization, however, requires that adjacent Fe cations be ferromagnetically coupled. Antiferromagnetic coupling results in distinguishable Fe2+ and Fe3+ cations. Electronic transitions between the Fe-Fe bonding and Fe-Fe antibonding orbitals results in the optically-induced intervalence charge transfer bands observed in the electronic spectra of mixed valence minerals. Such transitions are predicted to be polarized along the metal-metal bond direction, in agreement with experimental observations. ?? 1987 Springer-Verlag.

Sherman, D.M.

1987-01-01

316

Intermediate valence of plutonium chalcogenides as determined by photoemission  

NASA Astrophysics Data System (ADS)

There has been considerable experimental evidence, like magnetism, electrical conductivity, specific heat, lattice constant, elasticity and compressibility, showing that the plutonium monochalcogenides are intermediate valent and thus were the first actinide compounds where this aspect could be experimentally verified. Also, theoretical calculations confirm the experimental findings. Recently, photoemission has been performed on PuSe layers and PuTe single crystals and the findings have been interpreted as a 5f localization and not an intermediate valent configuration where 5f and 6d states hybridize. In this paper, it will be shown that also these photoemission data give direct evidence of intermediate valence. However, in addition, a narrow 5f band is observed at the Fermi level, causing the observed strongly enhanced Pauli paramagnetism.

Wachter, P.

2003-09-01

317

Valence-shell photoionization of chlorinelike Ar+ ions  

NASA Astrophysics Data System (ADS)

Absolute cross-section measurements for valence-shell photoionization of Ar+ ions are reported for photon energies ranging from 27.4 to 60.0 eV. The data, taken by merging beams of ions and synchrotron radiation at a photon energy resolution of 10 meV, indicate that the primary ion beam was a statistically weighted mixture of the 2P3/2o ground state and the 2P1/2o metastable state of Ar+. Photoionization of this Cl-like ion is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. Observed resonance line shapes indicate interference between indirect and direct photoionization channels. Resonance features are spectroscopically assigned and their energies and quantum defects are tabulated. The measurements are satisfactorily reproduced by theoretical calculations based on an intermediate coupling semirelativistic Breit-Pauli approximation.

Covington, A. M.; Aguilar, A.; Covington, I. R.; Hinojosa, G.; Shirley, C. A.; Phaneuf, R. A.; Álvarez, I.; Cisneros, C.; Dominguez-Lopez, I.; Sant'Anna, M. M.; Schlachter, A. S.; Ballance, C. P.; McLaughlin, B. M.

2011-07-01

318

Kondo destruction and valence fluctuations in an Anderson model.  

PubMed

Unconventional quantum criticality in heavy-fermion systems has been extensively analyzed in terms of a critical destruction of the Kondo effect. Motivated by a recent demonstration of quantum criticality in a mixed-valent heavy-fermion system, ?-YbAlB(4), we study a particle-hole-asymmetric Anderson impurity model with a pseudogapped density of states. We demonstrate Kondo destruction at a mixed-valent quantum critical point, where a collapsing Kondo energy scale is accompanied by a singular charge-fluctuation spectrum. Both spin and charge responses scale with energy over temperature (?/T) and magnetic field over temperature (H/T). Implications for unconventional quantum criticality in mixed-valence heavy fermions are discussed. PMID:23002763

Pixley, J H; Kirchner, Stefan; Ingersent, Kevin; Si, Qimiao

2012-08-24

319

Inter-Valence-Subband/Conduction-Band-Transport IR Detectors  

NASA Technical Reports Server (NTRS)

Infrared (IR) detectors characterized by a combination of (1) high-quantum-efficiency photoexcitation of inter-valence-subband transitions of charge carriers and (2) high-mobility conduction- band transport of the thus-excited charge carriers have been proposed in an effort to develop focal-plane arrays of such devices for infrared imaging. Like many prior quantum-well infrared photodetectors (QWIPs), the proposed devices would be made from semiconductor heterostructures. In order to obtain the combination of characteristics mentioned above, the proposed devices would be designed and fabricated in novel InAs/GaSb superlattice configurations that would exploit a phenomenon known in the semiconductor art as type-II broken-gap band offset.

Ting, David; Gunapala, Sarath; Bandara, Sumith

2004-01-01

320

Valence-shell photoionization of chlorine-like Ar$^{+}$ ions  

E-print Network

Absolute cross-section measurements for valence-shell photoionization of Ar$^{+}$ ions are reported for photon energies ranging from 27.4 eV to 60.0 eV. The data, taken by merging beams of ions and synchrotron radiation at a photon energy resolution of 10 meV, indicate that the primary ion beam was a statistically weighted mixture of the $^2P^o_{3/2}$ ground state and the $^2P^o_{1/2}$ metastable state of Ar$^{+}$. Photoionization of this C$\\ell$-like ion is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. Observed resonance lineshapes indicate interference between indirect and direct photoionization channels. Resonance features are spectroscopically assigned and their energies and quantum defects are tabulated. The measurements are satisfactorily reproduced by theoretical calculations based on an intermediate coupling semi-relativistic Breit-Pauli approximation.

Covington, A M; Covington, I R; Hinojosa, G; Shirley, C A; Álvarez, I; Cisneros, C; Dominguez-Lopez, I; Sant'Anna, M M; Schlachter, A S; Ballance, C P; McLaughlin, B M

2012-01-01

321

Insulation bonding test system  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

322

Excited states theory for optimized orbitals and valence optimized orbitals coupled-cluster doubles models  

E-print Network

Excited states theory for optimized orbitals and valence optimized orbitals coupled-cluster doubles May 2000; accepted 31 July 2000 We introduce an excited state theory for the optimized orbital coupled cluster doubles OO-CCD and valence optimized orbital coupled cluster doubles VOO-CCD models. The equations

Krylov, Anna I.

323

EELS analysis of cation valence states and oxygen vacancies in magnetic oxides  

E-print Network

EELS analysis of cation valence states and oxygen vacancies in magnetic oxides Z.L. Wang*, J.S. Yin with mixed valences of transition elements. Electron energy- loss spectroscopy (EELS) in the transmission of practical importance. This paper reports our current progress in applying EELS for quantitative

Wang, Zhong L.

324

VALENCE STATES OF SULFUR IN POLLUTION SAMPLES BY X-RAY ANALYSIS  

EPA Science Inventory

A flat single crystal spectrometer was configured to measure the valence band x-ray spectra of various forms of sulfur in air pollutants. While most different valence states showed differences in the structure of the K sub beta band, particular emphasis was placed on distinguishi...

325

Effects of hedonic valence and physiological arousal on emotion: A comparison of two theoretical perspectives  

Microsoft Academic Search

Two theoretical perspectives concerned with how one emotional state may influence a subsequent one were examined. Zillmann's (1979) excitation transfer theory suggests that undetected residual arousal from a first state will transfer and intensify a subsequent state—regardless of the first state's hedonic valence. Baron's (1977) incompatible response model, on the other hand, suggests that the hedonic valence of an earlier

Nyla R. Branscombe

1985-01-01

326

I-Space: The Effects of Emotional Valence and Source of Music on Interpersonal Distance  

E-print Network

I-Space: The Effects of Emotional Valence and Source of Music on Interpersonal Distance Ana personal space, that is, the emotionally-tinged zone around the human body that people feel is ``their space''. We evaluated the effects of emotional valence (positive versus negative) and source (external

Sheldon, Nathan D.

327

Group Motivation and Group Task Performance: The Expectancy-Valence Theory Approach.  

ERIC Educational Resources Information Center

Investigated effects of group motivation on group task performance. Created two levels of valence, expectancy and instrumentality. Valence variable reflected on group productivity on unstructured and task persistence measures. Expectancy variable's effect was on task persistence measure. Instrumentality affected group productivity on structured…

Nakanishi, Masayuki

1988-01-01

328

Ultrafast valence intersubband hole relaxation in InGaN multiple-quantum-well laser diodes  

E-print Network

the conduction band and the three valence bands can be derived from the symmetry properties of the zone center, California 93106-9560 Chi-Kuang Sun Department of Electrical Engineering and Graduate Institute of Electro selectively excite and probe different valence-subband-to-conduction-subband transitions in the MQW structure

Bowers, John

329

Valence, coordination number, and PAV cells in metallic rare earth compounds F. L. Carter  

E-print Network

Valence, coordination number, and PAV cells in metallic rare earth compounds F. L. Carter Naval, generalized coordination numbers, and Pauling's metallic valences are given for 24 intermetallic rare earth self-consistently it was necessary to increase the rare earth metal (/-character and hence decrease

Paris-Sud XI, Université de

330

Spin fluctuations effects on the low temperature properties of paramagnetic intermediate valence and Kondo compounds  

E-print Network

in the literature [7, 5] a Kondo lattice model to describe these intermediate valence compounds; the model has, so of the Kondo lattice the conclusions agreed on in the literature for the ground state of a Kondo impurity [8 valence and Kondo compounds M. T. Béal-Monod Laboratoire de Physique des Solides (*), Université Paris

Boyer, Edmond

331

PREPARATION OF STANDARDS FOR VALENCE STATE MEASUREMENT BY X-RAY FLUORESCENCE  

EPA Science Inventory

The preparation and characterization of standard samples representing several valence states for sulfur, vanadium, and chromium are described. The standards will be used by the U.S. Environmental Protection Agency to investigate the potential for determining valence state by high...

332

Cooperativity in beryllium bonds.  

PubMed

A theoretical study of the beryllium bonded clusters of the (iminomethyl)beryllium hydride and (iminomethyl)beryllium fluoride [HC(BeX)=NH, X = H, F] molecules has been carried out at the B3LYP/6-311++G(3df,2p) level of theory. Linear and cyclic clusters have been characterized up to the decamer. The geometric, energetic, electronic and NMR properties of the clusters clearly indicate positive cooperativity. The evolution of the molecular properties, as the size of the cluster increases, is similar to those reported in polymers held together by hydrogen bonds. PMID:24452820

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

2014-03-01

333

Teachers' Domain: Ionic Bonding  

NSDL National Science Digital Library

This Flash interactive tutorial explores ionic bondingâa type of chemical bond formed between two ions with opposite charges. Learners investigate how the transfer of electrons between atoms creates ions and how the mutual attraction of these charged particles forms ionic bonds. It also discusses trends in the periodic table to help learners comprehend how the structure of an ionic compound relates to its formula. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-16

334

Thread bonds in molecules  

E-print Network

Unusual chemical bonds are proposed. Each bond is almost covalent but is characterized by the thread of a small radius $\\sim 0.6\\times 10^{-11}$cm, between two nuclei in a molecule. The main electron density is concentrated outside the thread as in a covalent bond. The thread is formed by the electron wave function which has a tendency to be singular on it. The singularity along the thread is cut off by electron "vibrations" due to the interaction with zero point electromagnetic oscillations. The electron energy has its typical value of (1-10)eV. Due to the small tread radius the uncertainty of the electron momentum inside the thread is large resulting in a large electron kinetic energy $\\sim 1 MeV$. This energy is compensated by formation of a potential well due to the reduction of the energy of electromagnetic zero point oscillations. This is similar to formation of a negative van der Waals potential. Thread bonds are stable and cannot be created or destructed in chemical or optical processes.

Ivlev, B

2015-01-01

335

Bonded Retainers - Clinical Reliability  

Microsoft Academic Search

Bonded retainers have become a very important retention appliance in orthodontic treatment. They are popular because they are considered reliable, independent of patient cooperation, highly efficient, easy to fabricate, and almost invisible. Of these traits, reliability is the subject of this clinical study. A total of 549 patients with retainers were analyzed with regard to wearing time, extension of the

Dietmar Segner; Bettina Heinrici

2000-01-01

336

Dialogic Bonds and Boundaries.  

ERIC Educational Resources Information Center

A study of literature cannot be divorced from cultural contexts, nor can it ignore the humanist vision in interpreting literary texts. To discover dialogic bonds and boundaries between the reader and the text, or the writer and the audience, English classes should have two objectives: (1) to explore the diversity of perspectives, and (2) to relate…

Khawaja, Mabel

337

Photochemical tissue bonding  

DOEpatents

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

Redmond, Robert W. (Brookline, MA); Kochevar, Irene E. (Charlestown, MA)

2012-01-10

338

Flax Fiber - Interfacial Bonding  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

339

Bonding without Tears.  

ERIC Educational Resources Information Center

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

Akeroyd, F. Michael

1982-01-01

340

Influence of 5f electrons on structure and bonding in the actinide-hydrogen intermetallics  

SciTech Connect

Complexa phases form for the Th + H and U + H systems that are found with no other metals. In the Pa + H system, simple bcc C15 Laves and A15 phases can form, dependent on temperature and composition. The phase transformations appear to b magnetically driven, as a resutl of the decoupling of the metallic 5f electron bonding that occurs during hydriding; the C15 phases contain two kinds of Pa atoms-the one sublattice being still fully f-bonded and the other magnetic. This is a unique situation in solid state physics which defies a valence description. A similar situation obtains for A15 ..beta.. - UH/sub 3/ structure. The parent metals themselves exhibit electronegativities not unlike those of the mid-3d transition metals (e.g., Fe) because the valence electrons re tied up in metallic bonding. However, under the driving force for hydriding, the lattices can open up, decoupling the f-bonding and inducing magnetism. The systems then aggressively form very stable hydrides typical of highly-electropositive metals. Beyond uranium the trivalent metallic state is favored and rare-earth-like hydrides are found for Np + H and Pu + H. Nevertheless, the solid-state and transport properties are markedly different than for the rare-earth hydrides, showing that the latent influence of the 5f electrons is still strong.

Ward, J.W.

1984-01-01

341

Core excitation in O3 localized to one of two symmetry-equivalent chemical bonds: molecular alignment through vibronic coupling.  

PubMed

Core excitation from terminal oxygen OT in O3 is shown to be an excitation from a localized core orbital to a localized valence orbital. The valence orbital is localized to one of the two equivalent chemical bonds. We experimentally demonstrate this with the Auger-Doppler effect which is observable when O3 is core excited to the highly dissociative OT1s(-1)7a1 1 state. Auger electrons emitted from the atomic oxygen fragment carry information about the molecular orientation relative to the electromagnetic-field vector at the moment of excitation. The data together with analytical functions for the electron-peak profiles give clear evidence that the preferred molecular orientation for excitation only depends on the orientation of one bond, not on the total molecular orientation. The localization of the valence orbital "7a1" is caused by mixing of the valence orbital "5b2" through vibronic coupling of antisymmetric stretching mode with b2 symmetry. To the best of our knowledge, it is the first discussion of the localization of a core excitation of O3. This result explains the success of the widely used assumption of localized core excitation in adsorbates and large molecules. PMID:15945631

Wiesner, K; Naves de Brito, A; Sorensen, S L; Kosugi, N; Björneholm, O

2005-04-15

342

Empirical valence bond simulations of the hydride transfer step in the monoamine oxidase B catalyzed metabolism of dopamine.  

PubMed

Monoamine oxidases (MAOs) A and B are flavoenzymes responsible for the metabolism of biogenic amines such as dopamine, serotonin and noradrenaline. In this work, we present a comprehensive study of the rate-limiting step of dopamine degradation by MAO B, which consists in the hydride transfer from the methylene group of the substrate to the flavin moiety of the FAD prosthetic group. This article builds on our previous quantum chemical study of the same reaction using a cluster model (Vianello et al., Eur J Org Chem 2012; 7057), but now considering the full dimensionality of the hydrated enzyme with extensive configurational sampling. We show that MAO B is specifically tuned to catalyze the hydride transfer step from the substrate to the flavin moiety of the FAD prosthetic group and that it lowers the activation barrier by 12.3 kcal mol(-1) compared to the same reaction in aqueous solution, a rate enhancement of more than nine orders of magnitude. Taking into account the deprotonation of the substrate prior to the hydride transfer reaction, the activation barrier in the enzyme is calculated to be 16.1 kcal mol(-1), in excellent agreement with the experimental value of 16.5 kcal mol(-1). Additionally, we demonstrate that the protonation state of the active site residue Lys296 does not have an influence on the hydride transfer reaction. PMID:25220264

Repi?, Matej; Vianello, Robert; Purg, Miha; Duarte, Fernanda; Bauer, Paul; Kamerlin, Shina C L; Mavri, Janez

2014-12-01

343

Orthodontic bonding to porcelain: A comparison of bonding systems  

Microsoft Academic Search

Statement of problem. Direct bonding of orthodontic brackets to porcelain surfaces has been plagued by failure. Purpose. The purpose of this study was to compare the bond strengths of several different bonding systems when bonding orthodontic brackets to porcelain-fused-to-metal surfaces. Material and methods. Fifty natural glazed feldspathic porcelain-fused-to-noble metal disks 6 mm in diameter and 3 mm in height (1

Dianne D. Pannes; Daniel K. Bailey; Jeffrey Y. Thompson; Daniel M. Pietz

2003-01-01

344

Interfacial chemical bonding state and band alignment of CaF{sub 2}/hydrogen-terminated diamond heterojunction  

SciTech Connect

CaF{sub 2} films are deposited on hydrogen-terminated diamond (H-diamond) by a radio-frequency sputter-deposition technique at room temperature. Interfacial chemical bonding state and band alignment of CaF{sub 2}/H-diamond heterojunction are investigated by X-ray photoelectron spectroscopy. It is confirmed that there are only C-Ca bonds at the CaF{sub 2}/H-diamond heterointerface. Valence and conductance band offsets of the CaF{sub 2}/H-diamond heterojunciton are determined to be 3.7 {+-} 0.2 and 0.3 {+-} 0.2 eV, respectively. It shows a type I straddling band configuration. The large valence band offset suggests advantage of the CaF{sub 2}/H-diamond heterojunciton for the development of high power and high frequency field effect transistors.

Liu, J. W.; Liao, M. Y.; Cheng, S. H.; Imura, M. [Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Koide, Y. [Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Nanofabrication Platform, NIMS, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Center of Materials Research for Low Carbon Emission (CMRLC), NIMS, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2013-03-28

345

Improving humidity bond reliability of copper bonding wires  

Microsoft Academic Search

There is growing interest in Cu wire bonding for LSI interconnection due to cost savings and better electrical and mechanical properties. Conventional bare Cu bonding wires, in general, are severely limited in their use compared to Au wires. A coated Cu bonding wire (EX1) has been developed for LSI application. EX1 is a Pd-coated Cu wire to enhance the bondability.

Tomohiro Uno; Takashi Yamada

2010-01-01

346

Correlation among electronegativity, cation polarizability, optical basicity and single bond strength of simple oxides  

SciTech Connect

A suitable relationship between free-cation polarizability and electronegativity of elements in different valence states and with the most common coordination numbers has been searched on the basis of the similarity in physical nature of both quantities. In general, the cation polarizability increases with decreasing element electronegativity. A systematic periodic change in the polarizability against the electronegativity has been observed in the isoelectronic series. It has been found that generally the optical basicity increases and the single bond strength of simple oxides decreases with decreasing the electronegativity. The observed trends have been discussed on the basis of electron donation ability of the oxide ions and type of chemical bonding in simple oxides. - Graphical abstract: This figure shows the single bond strength of simple oxides as a function of element electronegativity. A remarkable correlation exists between these independently obtained quantities. High values of electronegativity correspond to high values of single bond strength and vice versa. It is obvious that the observed trend in this figure is closely related to the type of chemical bonding in corresponding oxide. Highlights: Black-Right-Pointing-Pointer A suitable relationship between free-cation polarizability and electronegativity of elements was searched. Black-Right-Pointing-Pointer The cation polarizability increases with decreasing element electronegativity. Black-Right-Pointing-Pointer The single bond strength of simple oxides decreases with decreasing the electronegativity. Black-Right-Pointing-Pointer The observed trends were discussed on the basis of type of chemical bonding in simple oxides.

Dimitrov, Vesselin, E-mail: vesselin@uctm.edu [Department of Silicate Technology, University of Chemical Technology and Metallurgy, 8, Kl. Ohridski Blvd., Sofia 1756 (Bulgaria)] [Department of Silicate Technology, University of Chemical Technology and Metallurgy, 8, Kl. Ohridski Blvd., Sofia 1756 (Bulgaria); Komatsu, Takayuki, E-mail: komatsu@mst.nagaokaut.ac.jp [Department of Materials Science and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan)] [Department of Materials Science and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan)

2012-12-15

347

Identification of Ectonucleotide Pyrophosphatase/Phosphodiesterase 3 (ENPP3) as a Regulator of N-Acetylglucosaminyltransferase GnT-IX (GnT-Vb)*  

PubMed Central

Our previous studies on a ?1,6-N-acetylglucosaminyltransferase, GnT-IX (GnT-Vb), a homolog of GnT-V, indicated that the enzyme has a broad GlcNAc transfer activity toward N-linked and O-mannosyl glycan core structures and that its brain-specific gene expression is regulated by epigenetic histone modifications. In this study, we demonstrate the existence of an endogenous inhibitory factor for GnT-IX that functions as a key regulator for GnT-IX enzymatic activity in Neuro2a (N2a) cells. We purified this factor from N2a cells and found that it is identical to ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3), as evidenced by mass spectrometry and by the knockdown and overexpression of ENPP3 in cultured cells. Kinetic analyses revealed that the mechanism responsible for the inhibition of GnT-IX caused by ENPP3 is the ENPP3-mediated hydrolysis of the nucleotide sugar donor substrate, UDP-GlcNAc, with the resulting generation of UMP, a potent and competitive inhibitor of GnT-IX. Indeed, ENPP3 knockdown cells had significantly increased levels of intracellular nucleotide sugars and displayed changes in the total cellular glycosylation profile. In addition to chaperones or other known regulators of glycosyltransferases, the ENPP3-mediated hydrolysis of nucleotide sugars would have widespread and significant impacts on glycosyltransferase activities and would be responsible for altering the total cellular glycosylation profile and modulating cellular functions. PMID:23960081

Korekane, Hiroaki; Park, Jong Yi; Matsumoto, Akio; Nakajima, Kazuki; Takamatsu, Shinji; Ohtsubo, Kazuaki; Miyamoto, Yasuhide; Hanashima, Shinya; Kanekiyo, Kenji; Kitazume, Shinobu; Yamaguchi, Yoshiki; Matsuo, Ichiro; Taniguchi, Naoyuki

2013-01-01

348

hp calculators HP 50g Bond Yield  

E-print Network

rate the bond pays is fixed when the bond is first sold or issued, but changes in the market interesthp calculators HP 50g Bond Yield The FINANCE menu Bond Yield Practice solving for the yield of a bond #12;hp calculators HP 50g Bond Yield hp calculators - 2 - HP 50g Bond Yield The FINANCE menu

Vetter, Frederick J.

349

Developmental reversals in false memory: Effects of emotional valence and arousal.  

PubMed

Do the emotional valence and arousal of events distort children's memories? Do valence and arousal modulate counterintuitive age increases in false memory? We investigated those questions in children, adolescents, and adults using the Cornell/Cortland Emotion Lists, a word list pool that induces false memories and in which valence and arousal can be manipulated factorially. False memories increased with age for unpresented semantic associates of word lists, and net accuracy (the ratio of true memory to total memory) decreased with age. These surprising developmental trends were more pronounced for negatively valenced materials than for positively valenced materials, they were more pronounced for high-arousal materials than for low-arousal materials, and developmental increases in the effects of arousal were small in comparison with developmental increases in the effects of valence. These findings have ramifications for legal applications of false memory research; materials that share the emotional hallmark of crimes (events that are negatively valenced and arousing) produced the largest age increases in false memory and the largest age declines in net accuracy. PMID:20547393

Brainerd, C J; Holliday, R E; Reyna, V F; Yang, Y; Toglia, M P

2010-10-01

350

High and low roads to odor valence? A choice response-time study  

PubMed Central

Valence and edibility are two important features of olfactory perception, but it remains unclear how they are read out from an olfactory input. For a given odor object (e.g., the smell of rose or garlic), does perceptual identification of that object necessarily precede retrieval of information about its valence and edibility, or alternatively, are these processes independent? In the present study, we studied rapid, binary perceptual decisions regarding odor detection, object identity, valence, and edibility for a set of common odors. We found that decisions regarding odor-object identity were faster than decisions regarding odor valence or edibility, but slower than detection. Mediation analysis revealed that odor valence and edibility decision response times were predicted by a model in which odor-object identity served as a mediator along the perceptual pathway from detection to both valence and edibility. According to this model, odor valence is determined through both a “low road” that bypasses odor objects and a “high road” that utilizes odor-object information. Edibility evaluations are constrained to processing via the high road. The results outline a novel causal framework that explains how major perceptual features might be rapidly extracted from odors through engagement of odor objects early in the processing stream. PMID:23875569

Olofsson, Jonas K.; Bowman, Nicholas E.; Gottfried, Jay A.

2014-01-01

351

ChemTeacher: Metallic Bonds  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Metallic Bonds page includes resources for teaching students about metallic bonding.

2011-01-01

352

ChemTeacher: Ionic Bonds  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Ionic Bonds page includes resources for teaching students about ionic bonding.

2011-01-01

353

The Illiquidity of Corporate Bonds  

E-print Network

This paper examines the illiquidity of corporate bonds and its asset-pricing implications. Using transactions data from 2003 to 2009, we show that the illiquidity in corporate bonds is substantial, significantly greater ...

Bao, Jack

354

Positively Valenced Stimuli Facilitate Creative Novel Metaphoric Processes by Enhancing Medial Prefrontal Cortical Activation  

PubMed Central

A metaphor is a figure of speech in which a subject is symbolic of another unrelated object. In the present study, we examined neural patterns associated with both novel unfamiliar and conventional familiar metaphoric processing, and how these patterns are modulated by affective valence. Prior to fMRI scanning, participants received a list of word pairs (novel unfamiliar metaphors as well as conventional familiar metaphors) and were asked to denote the valence (positive, negative, or neutral) of each word pair. During scanning, participants had to decide whether the word pairs formed meaningful or meaningless expressions. Results indicate that participants were faster and more accurate at deciding that positively valenced metaphors were meaningful compared to neutral metaphors. These behavioral findings were accompanied by increased activation in the medial prefrontal cortex (mPFC), posterior cingulate cortex (PCC), and the right inferior parietal lobe (RIPL). Specifically, positively valenced novel unfamiliar metaphors elicited activation in these brain regions in addition to the left superior temporal gyrus when compared to neutral novel metaphors. We also found that the mPFC and PCC mediated the processing of positively valenced metaphors when compared to negatively valenced metaphors. Positively valenced conventional metaphors, however, elicited different neural signatures when contrasted with either neutral or negatively valenced conventional metaphors. Together, our results indicate that positively valenced stimuli facilitate creative metaphoric processes (specifically novel metaphoric processes) by mediating attention and cognitive control processes required for the access, integration, and selection of semantic associations via modulation of the mPFC. The present study is important for the development of neural accounts of emotion-cognition interactions required for creativity, language, and successful social functioning in general. PMID:23637686

Subramaniam, Karuna; Beeman, Mark; Faust, Miriam; Mashal, Nira

2013-01-01

355

Characterization of CF bonds with multiple-bond character: bond lengths, stretching force constants, and bond dissociation energies.  

PubMed

Isoelectronic C=F(+) and C=O bonds contained in fluoro-substituted carbenium ions, aldehydes, and ketones are investigated with regard to their bond properties by utilizing the vibrational spectra of these molecules. It is demonstrated that bond dissociation energies (BDEs), bond lengths, vibrational stretching frequencies, and bond densities are not reliable descriptors of the bond strength. The latter is related to the intrinsic BDE, which corresponds to nonrelaxed dissociation products retaining the electronic structure and geometry they have in the molecule. It is shown that the harmonic stretching force constants k(a) of the localized internal coordinate vibrations (adiabatic vibrational modes) reflect trends in the intrinsic BDEs. The k(a) values of both CO and CF bonds are related to the bond lengths through a single exponential function. This observation is used to derive a common bond order n for 46 CO- and CF-containing molecules that reliably describes differences in bonding. CF bonds in fluorinated carbenium ions possess bond orders between 1.3 and 1.7 as a result of significant pi back-bonding from F to C, which is sensitive to electronic effects caused by substituents at the carbenium center. Therefore, the strength of the C=F(+) bond can be used as a sensor for (hyper)conjugation and other electronic effects influencing the stability of the carbenium ion. The diatomic C=F(+) ion has a true double bond due to pi donation from the F atom. The characterization of CF bonds with the help of adiabatic stretching modes is also applied to fluoronium ions (n = 0.3-0.6) and transition states involving CF cleavage and HF elimination (n = 0.7-0.8). PMID:19152353

Kraka, Elfi; Cremer, Dieter

2009-03-01

356

The Evolution of Bond Theory  

NSDL National Science Digital Library

In chemistry lectures we have little time to discuss the history of chemistry. This simulation begins with the development of valence concepts in the 19th century. We will step back into the 19th century to see how theories of chemical combination changed during that time.

357

Valency-dependent affinity of bioactive hydroxyapatite-binding dendrons.  

PubMed

Hydroxyapatite (HA)-coated surfaces are used widely as stationary phase for protein and enzyme purification, coatings for dental and orthopedic implants, and composite materials for tissue engineering substrates. More advanced applications are envisioned, but progress has been slowed by the limited ability to controllably functionalize the surface of HA with biomolecules in a translationally relevant manner. Herein we report the synthesis and characterization of a series of multivalent, HA-binding peptide bioconjugates with variable valency and tether length which afford the ability to precisely tune the desired binding behavior. The respective binding affinities of the multivalent constructs to HA surface were characterized by quartz crystal microbalance with dissipation monitoring (QCM-D) techniques, and the relationship between dendron structure and binding affinity was revealed. Tetravalent constructs of HA-binding peptides show a 100-fold enhancement in binding affinity compared to HA-binding peptide sequences reported previously. Both biotin and bone morphogenic protein-2 (BMP-2) derivative peptide were successfully linked to the focal point as initial demonstrations. PMID:23931528

Tang, Wen; Ma, Yanrui; Xie, Sibai; Guo, Kai; Katzenmeyer, Bryan; Wesdemiotis, Chrys; Becker, Matthew L

2013-09-01

358

Photoion mass spectroscopy and valence photoionization of hypoxanthine, xanthine and caffeine  

NASA Astrophysics Data System (ADS)

Photoionization mass spectra of hypoxanthine, xanthine and caffeine were measured using the photoelectron-photoion coincidence technique and noble gas resonance radiation at energies from 8.4 to 21.2 eV for ionization. The fragmentation patterns for these compounds show that hydrogen cyanide is the main neutral loss species at higher photon energies, while photoionization below 16.67 eV led predominantly to the parent ion. The valence photoelectron spectra of this family of molecules were measured over an extended energy range, including the inner C, N and O 2s valence orbitals. The observed ion fragments were related to ionization of the valence orbitals.

Feyer, Vitaliy; Plekan, Oksana; Richter, Robert; Coreno, Marcello; Prince, Kevin C.

2009-03-01

359

The outer valence orbital momentum profiles of thiophene by electron momentum spectroscopy  

NASA Astrophysics Data System (ADS)

We report here the first measurements of the complete valence shell binding energy spectra and the outer valence orbital momentum profiles of thiophene, using a high resolution binary (e, 2e) electron momentum spectrometer, at an impact energy of 1200 eV plus the binding energy and using symmetric non-coplanar kinematics. Binding energy spectra of the complete valence shell have been obtained. The summed experimental momentum profile of the HOMO 1a 2 and NHOMO 3b 1 is compared with the theoretical momentum distributions calculated using Hartree-Fock and density functional theory methods with various basis sets. The experimental measurement is well described by the calculations.

Zhang, S. F.; Ren, X. G.; Su, G. L.; Ning, C. G.; Zhou, H.; Li, B.; Huang, F.; Li, G. Q.; Deng, J. K.

2005-01-01

360

Valence Shell Ionization Spectra of Propane by (e, 2e) Spectroscopy  

NASA Astrophysics Data System (ADS)

The measurements of the valence shell ionisation energy spectra (6-32 eV) for propane (C3H8) by high resolution (?E = 0.9 eV and ?p = 0.1 a.u.) (e, 2e) spectrometer at impact energy of 1200 eV plus binding energy and symmetric noncoplanar kinematics are reported. The spectrum is consistent with a single particle picture of ionization from each of the seven outer-valence orbitals and the three inner-valence orbitals. The ionization energies are in agreement with published photoelectron spectroscopy data.

Pang, Wen-ning; Zhang, Wen-xin; Gao, Nai-fei; Shang, Ren-cheng; Deng, Jing-kang; Chen, Xue-jun

1998-09-01

361

Cyclic Bonds in Branched Polymers  

E-print Network

In the gelation theory it has been implicitly assumed that (I) a cyclic bond is a finite bond that returns to itself; (II) cyclic bonds distribute at random in network structures. In this paper these two assumptions are reexamined from a new point of view. The physical soundness of the assumptions are assessed through comparison with experimental observations.

Kazumi Suematsu

2015-02-12

362

Bond financing in volatile times.  

PubMed

A competitive landscape for providers and changing market conditions require an understanding of key capital sources: tax-exempt bonds remain an attractive capital source. Credit enhancement for bonds is more expensive and more difficult to find than it was in years past. Direct bond purchases by commercial banks mitigate the traditional risks. PMID:24701850

Gould, Kenneth A; Blanda, Christopher M

2014-03-01

363

Rapid Adhesive Bonding of Composites  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

364

New Materials for Bonding Wire  

Microsoft Academic Search

In this paper, Insulated wire for Fine pad pitch bonding and 3D PKG technology, Cu wire and Au-Ag wire for cost reduction, and Ag wire in response to bond pad metallization change are reviewed from technology aspect. With only few tens of nanometers thick coating layer, insulated wire forms stable free air ball with good 1 st bond bondability. As

Jeong Tak Moon; June Sub Hwang; Jong Su Cho; Seong Hyoun Kim

365

46 CFR Sec. 10 - Bonds.  

Code of Federal Regulations, 2010 CFR

...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

2010-10-01

366

46 CFR Sec. 10 - Bonds.  

Code of Federal Regulations, 2011 CFR

...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

2011-10-01

367

46 CFR Sec. 10 - Bonds.  

Code of Federal Regulations, 2012 CFR

...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

2012-10-01

368

46 CFR Sec. 10 - Bonds.  

Code of Federal Regulations, 2014 CFR

...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

2014-10-01

369

46 CFR Sec. 10 - Bonds.  

Code of Federal Regulations, 2013 CFR

...AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 10 Bonds...payment bonds required by Article 14 of the NSA-LUMPSUMREP Contract. The stand- ard...payment bond requirements of Article 14 of the NSA-LUMPSUMREP Contract, the...

2013-10-01

370

Solder Bonded Optoelectronic Transceiver Components  

Microsoft Academic Search

solder bonded optical modulator and detector arrays on silicon VLSI circuits, together with solder bonded lasers and micro-fabricated silicon packaging are described. These approaches are being used for integrated components for optical interconnect applications. Introduction. integration using solder bonding enables optimised optoelectronic and electronic components to be combined for a wide range of applications, particularly in optical interconnect where the

A. J. Moseley; M. J. Goodwin

1993-01-01

371

Bonding characteristics, thermal expansibility, and compressibility of RXO(4) (R = rare earths, X = P, As) within monazite and zircon structures.  

PubMed

Systematically theoretical research was performed on the monazite- and zircon-structure RXO(4) (R = Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; X = P, As) series by using the chemical bond theory of dielectric description. The chemical bond properties of R-O and X-O bonds were presented. In the zircon phase, the covalency fractions of X-O bonds increased in the order of V-O < As-O < P-O, which was in accordance with the ionic radii and electronegative trends, and the covalency fractions of R-O bonds varied slightly due to the lanthanide contraction. While in the monazite phase, both R-O and X-O bonds were divided into two groups by their covalency fractions. The contributions from the bond to the lattice energy, linear thermal expansion coefficient (LTEC), and bulk modulus were explored. The X-O bonds with short bond lengths and high chemical valence made greater contributions to the lattice energy and performed nearly rigidly during the deformation. A regular variation of lattice energy, LTEC, and bulk modulus with the ionic radii of the lanthanides was observed in both monazite and zircon phases. PMID:19323526

Li, Huaiyong; Zhang, Siyuan; Zhou, Shihong; Cao, Xueqiang

2009-05-18

372

Pentaatomic planar tetracoordinate silicon with 14 valence electrons: A large-scale global search of SiXnYmq (n?+?m?=?4; q?=?0, ±1, -2; X, Y?=?main group elements from H to Br).  

PubMed

Designing and characterizing the compounds with exotic structures and bonding that seemingly contrast the traditional chemical rules are a never-ending goal. Although the silicon chemistry is dominated by the tetrahedral picture, many examples with the planar tetracoordinate-Si skeletons have been discovered, among which simple species usually contain the 17/18 valence electrons. In this work, we report hitherto the most extensive structural search for the pentaatomic ptSi with 14 valence electrons, that is, SiXnYmq (n?+?m?=?4; q?=?0, ±1, -2; X, Y?=?main group elements from H to Br). For 129 studied systems, 50 systems have the ptSi structure as the local minimum. Promisingly, nine systems, that is, Li3SiAs2-, HSiY3 (Y?=?Al/Ga), Ca3 SiAl(-) , Mg4 Si(2-) , C2 LiSi, Si3 Y2 (Y?=?Li/Na/K), each have the global minimum ptSi. The former six systems represent the first prediction. Interestingly, in HSiY3 (Y?=?Al/Ga), the H-atom is only bonded to the ptSi-center via a localized 2c-2e ? bond. This sharply contradicts the known pentaatomic planar-centered systems, in which the ligands are actively involved in the ligand-ligand bonding besides being bonded to the planar center. Therefore, we proposed here that to generalize the 14e-ptSi, two strategies can be applied as (1) introducing the alkaline/alkaline-earth elements and (2) breaking the peripheral bonding. In light of the very limited global ptSi examples, the presently designed six systems with 14e are expected to enrich the exotic ptSi chemistry and welcome future laboratory confirmation. © 2014 Wiley Periodicals, Inc. PMID:25430676

Xu, Jing; Ding, Yi-Hong

2015-03-01

373

Coexistence of solvated electron and benzene-centered valence anion in the negatively charged benzene-water clusters  

NASA Astrophysics Data System (ADS)

We present a combined M06 functional calculation and ab initio molecular dynamics simulation study of an excess electron (EE) in a microhydrated aromatic complex (modeled by benzene (Bz)-water binary clusters, Bz(H2O)n). Calculated results illustrate that Bz ring and water clusters are indeed linked through the ?⋯HO interactions in the neutral Bz(H2O)n (n = 1-8) clusters, and the size of the water cluster does not influence the nature of its interaction with the ? system for the oligo-hydrated complexes. The states and the dynamics of an EE trapped in such Bz-water clusters were also determined. All of possible localized states for the EE can be roughly classified into two types: (i) single, ring-localized states (the Bz-centered valence anions) in which an EE occupies the LUMO of the complexes originating from the LUMO (?*) of the Bz ring, and the ?⋯HO interactions are enhanced for increase of electron density of the Bz ring. In this mode, the carbon skeleton of the Bz part is significantly deformed due to increase of electron density and nonsymmetric distribution of electron density induced by the interacting H-O bonds; (ii) solvated states, in which an EE is trapped directly as a surface state by the dangling hydrogen atoms of water molecules or as a solvated state in a mixed cavity formed by Bz and water cluster. In the latter case, Bz may also participate in capturing an EE using its C-H bonds in the side edge of the aromatic ring as a part of the cavity. In general, a small water cluster is favorable to the Bz-centered valence anion state, while a large one prefers a solvated electron state. Fluctuations and rearrangement of water molecules can sufficiently modify the relative energies of the EE states to permit facile conversion from the Bz-centered to the water cluster-centered state. This indicates that aromatic Bz can be identified as a stepping stone in electron transfer and the weak ?⋯HO interaction plays an important role as the driving force in conversion of the two states.

Zhang, Meng; Zhao, Jing; Liu, Jinxiang; Zhou, Lianwen; Bu, Yuxiang

2013-01-01

374

Metallic bond effects on mean excitation energies for stopping powers  

NASA Technical Reports Server (NTRS)

Mean excitation energies for first row metals are evaluated by means of the local plasma approximation. Particle corrections based on Pines' (1953) procedure and the Wigner Seitz (1934) model of the metallic state are included. The agreement with experimental values is remarkably good. In contrast to previous work, the calculations given here estimate shifts in the plasma frequency according to the theory for plane wave states in an extended plasma as calculated by Pines. It is demonstrated that the effects of the metallic bond in lithium and beryllium are quite large and that they appear mainly as a result of collective oscillations in the 'free' electron gas formed from the valence electrons. The usefulness of the plasma frequency shift derived for a degenerate electron gas in predicting the plasma frequency shift within the ion core is considered surprising.

Wilson, J. W.; Xu, Y. J.

1982-01-01

375

The role of hydrogen bonding in the enzymatic reaction catalyzed by HIV-1 protease  

PubMed Central

The hydrogen-bond network in various stages of the enzymatic reaction catalyzed by HIV-1 protease was studied through quantum-classical molecular dynamics simulations. The approximate valence bond method was applied to the active site atoms participating directly in the rearrangement of chemical bonds. The rest of the protein with explicit solvent was treated with a classical molecular mechanics model. Two possible mechanisms were studied, general-acid/general-base (GA/GB) with Asp 25 protonated at the inner oxygen, and a direct nucleophilic attack by Asp 25. Strong hydrogen bonds leading to spontaneous proton transfers were observed in both reaction paths. A single-well hydrogen bond was formed between the peptide nitrogen and outer oxygen of Asp 125. The proton was diffusely distributed with an average central position and transferred back and forth on a picosecond scale. In both mechanisms, this interaction helped change the peptide-bond hybridization, increased the partial charge on peptidyl carbon, and in the GA/GB mechanism, helped deprotonate the water molecule. The inner oxygens of the aspartic dyad formed a low-barrier, but asymmetric hydrogen bond; the proton was not positioned midway and made a slightly elongated covalent bond, transferring from one to the other aspartate. In the GA/GB mechanism both aspartates may help deprotonate the water molecule. We observed the breakage of the peptide bond and found that the protonation of the peptidyl amine group was essential for the peptide-bond cleavage. In studies of the direct nucleophilic mechanism, the peptide carbon of the substrate and oxygen of Asp 25 approached as close as 2.3 ?. PMID:14739332

Trylska, Joanna; Grochowski, Pawe?; McCammon, J. Andrew

2004-01-01

376

Thermal Variation of Ce Valence in Mixed Valence–Kondo Lattice Systems CeT2(Si1-xGex)2 with T= Mn and Ni  

SciTech Connect

The results on the thermal variation of Ce L3-valence in CeT2(Si1-xGex)2 series with 0{le}x{le}1 and T=Mn and Ni are reported. It is observed that for both series, the Ce valence increases with decreasing temperature and has little thermal variation for samples in the nearly trivalent regime. The magnitude of this thermal variation in the T=Mn series is much greater than in the T=Ni series. The results are explained by the degenerate Anderson model and correlated with the specific heat data.

Liang,G.; Croft, M.

2008-01-01

377

Silver(I) complexes of the weakly coordinating solvents SO(2) and CH(2)Cl(2): crystal structures, bonding, and energetics of [Ag(OSO)][Al{OC(CF(3))(3)}(4)], [Ag(OSO)(2/2)][SbF(6)], and [Ag(CH(2)Cl(2))(2)][SbF(6)].  

PubMed

Pushing the limits of coordination chemistry: The most weakly coordinated silver complexes of the very weakly coordinating solvents dichloromethane and liquid sulfur dioxide were prepared. Special techniques at low temperatures and the use of weakly coordinating anions allowed structural characterization of [Ag(OSO)][Al{OC(CF(3))(3)}(4)], [Ag(OSO)(2/2)][SbF(6)], and [Ag(Cl(2)CH(2))(2)][SbF(6)] (see figure). An investigation of the bonding shows that these complexes are mainly stabilized by electrostatic monopole-dipole interactions.The synthetically useful solvent-free silver(I) salt Ag[Al(pftb)(4)] (pftb=--OC(CF(3))(3)) was prepared by metathesis reaction of Li[Al(pftb)(4)] with Ag[SbF(6)] in liquid SO(2). The solvated complexes [Ag(OSO)][Al(pftb)(4)], [Ag(OSO)(2/2)][SbF(6)], and [Ag(CH(2)Cl(2))(2)][SbF(6)] were prepared and isolated by special techniques at low temperatures and structurally characterized by single-crystal X-ray diffraction. The SO(2) complexes provide the first examples of coordination of the very weak Lewis base SO(2) to silver(I). The SO(2) molecule in [Ag(OSO)][Al(pftb)(4)] is eta(1)-O coordinated to Ag(+), while the SO(2) ligands in [Ag(OSO)(2/2)][SbF(6)] bridge two Ag(+) ions in an eta(2)-O,O' (trans,trans) manner. [Ag(CH(2)Cl(2))(2)][SbF(6)] contains [Ag(CH(2)Cl(2))(2)](+) ions linked through [SbF(6)](-) ions to give a polymeric structure. The solid-state silver(I) ion affinities (SIA) of SO(2) and CH(2)Cl(2), based on bond lengths and corresponding valence units in the corresponding complexes and tensimetric titrations of Ag[Al(pftb)(4)] and Ag[SbF(6)] with SO(2) vapor, show that SO(2) is a weaker ligand to Ag(+) than the commonly used weakly coordinating solvent CH(2)Cl(2) and indicated that binding strength of SO(2) to silver(I) in the silver(I) salts increases with increasing size of the corresponding counteranion ([Al(pftb)(4)](-)>[SbF(6)](-)). The experimental findings are in good agreement with theoretical gas-phase ligand-binding energies of [Ag(L)(n)](+) (L=SO(2), CH(2)Cl(2); n=1, 2) and solid-state enthalpies obtained from Born-Fajans-Haber cycles by using the volume-based thermodynamics (VBT) approach. Bonding analysis (VB, NBO, MO) of [Ag(L)(n)](+) suggests that these complexes are almost completely stabilized by electrostatic interaction, that is, monopole-dipole interaction, with almost no covalent contribution by electron donation from the ligand orbitals into the vacant 5s orbital of Ag(+). All experimental findings and theoretical considerations demonstrate that SO(2) is less covalently bound to Ag(+) than CH(2)Cl(2) and support the thesis that SO(2) is a polar but non-coordinating solvent towards Ag(+). PMID:19449357

Decken, Andreas; Knapp, Carsten; Nikiforov, Grigori B; Passmore, Jack; Rautiainen, J Mikko; Wang, Xinping; Zeng, Xiaoqing

2009-06-22

378

An Intracranial EEG Study of the Neural Dynamics of Musical Valence Processing.  

PubMed

The processing of valence is known to recruit the amygdala, orbitofrontal cortex, and relevant sensory areas. However, how these regions interact remains unclear. We recorded cortical electrical activity from 7 epileptic patients implanted with depth electrodes for presurgical evaluation while they listened to positively and negatively valenced musical chords. Time-frequency analysis suggested a specific role of the orbitofrontal cortex in the processing of positively valenced stimuli while, most importantly, Granger causality analysis revealed that the amygdala tends to drive both the orbitofrontal cortex and the auditory cortex in theta and alpha frequency bands, during the processing of valenced stimuli. Results from the current study show the amygdala to be a critical hub in the emotion processing network: specifically one that influences not only the higher order areas involved in the evaluation of a stimulus's emotional value but also the sensory cortical areas involved in the processing of its low-level acoustic features. PMID:24904066

Omigie, Diana; Dellacherie, Delphine; Hasboun, Dominique; George, Nathalie; Clement, Sylvain; Baulac, Michel; Adam, Claude; Samson, Severine

2014-06-01

379

THE VALENCE AND METHYLATION STATE OF ARSENIC DETERMINES ITS POTENCY IN INTERACTION WITH THE MITOTIC APPARATUS  

EPA Science Inventory

We have previously shown that the cytotoxic and genotoxic potency of arsenicals is dependent upon their valence and methylation state. Trivalent methylated arsenicals are much more potent DNA damaging agents than are their inorganic and pentavalent counterparts. Furthermore, thei...

380

Optogenetic dissection of neural circuits underlying emotional valence and motivated behaviors  

E-print Network

The neural circuits underlying emotional valence and motivated behaviors are several synapses away from both defined sensory inputs and quantifiable motor outputs. Electrophysiology has provided us with a suitable means ...

Nieh, Horng-An Edward

381

Electronic structure of icosahedral AlMnPd quasicrystals from valence and core level photoemission  

NASA Astrophysics Data System (ADS)

A study of the electronic structure of quasicrystals is important for an understanding of the unusual physical properties of these materials. We have investigated the core and valence level photoemission of icosahedral AlPdMn quasicrystals using synchrotron radiation. Spectra were recorded from the fivefold surface of cleaved crystals (in order to provide unperturbed stoichiometry) as well as sputter/annealed surfaces which exhibit good quasicrystalline order. The intensities of the core level lines exhibit a pronounced dependence on polar and azimuthal emission angle which is attributed to photoelectron diffraction effects. Resonance and cross section effects were used to identify the contribution of the different constituent atoms to the valence level region. The valence level emission also shows a clear intensity dependence as a function of emission angle, reflecting the symmetry of the valence states in these compounds. These results are interpreted in terms of the electronic structure of quasicrystals with reference to recent theoretical work.

Barman, S. R.; Paggel, J. J.; Gehrmann, S.; Horn, K.; Rotenberg, E.; Ebert, Ph.; Urban, K.

1998-03-01

382

Electronic structure and bonding of the 3d transition metal borides, MB, M =Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu through all electron ab initio calculations  

NASA Astrophysics Data System (ADS)

The electronic structure and bonding of the ground and some low-lying states of all first row transition metal borides (MB), ScB, TiB, VB, CrB, MnB, FeB, CoB, NiB, and CuB have been studied by multireference configuration interaction (MRCI) methods employing a correlation consistent basis set of quintuple cardinality (5Z). It should be stressed that for all the above nine molecules, experimental results are essentially absent, whereas with the exception of ScB and CuB the remaining seven species are studied theoretically for the first time. We have constructed full potential energy curves at the MRCI/5Z level for a total of 27 low-lying states, subsequently used to extract binding energies, spectroscopic parameters, and bonding schemes. In addition, some 20 or more states for every MB species have been examined at the MRCI/4Z level of theory. The ground state symmetries and corresponding binding energies (in kcal/mol) are ?-5(ScB), 76; ?6(TiB), 65; ?+7(VB), 55; ?+6(CrB), 31; ?5(MnB), 20; ?-4(FeB), 54; ?3(CoB), 66; ?+2(NiB), 79; and ?+1(CuB), 49.

Tzeli, Demeter; Mavridis, Aristides

2008-01-01

383

77 FR 32128 - Cancellation of Bond Subject to Enhanced Bonding Requirements Upon CBP's Acceptance of Qualified...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Cancellation of Bond Subject to Enhanced Bonding Requirements Upon CBP's Acceptance of...amount was calculated pursuant to enhanced bonding requirements (EBR bond) upon the agency's...INFORMATION: Background I. Enhanced Bonding Requirements In 2004, U.S....

2012-05-31

384

Chiral Perturbation Theory for Staggered Sea Quarks and Ginsparg-Wilson Valence Quarks  

E-print Network

We study lattice QCD with staggered sea and Ginsparg-Wilson valence quarks. The Symanzik effective action for this mixed lattice theory, including the lattice spacing contributions of O(a^2), is derived. Using this effective theory we construct the leading order chiral Lagrangian. The masses and decay constants of pseudoscalars containing two Ginsparg-Wilson valence quarks are computed at one loop order.

Oliver Baer; Claude Bernard; Gautam Rupak; Noam Shoresh

2005-03-10

385

Valence state of cerium in the hexagonal CeM5 compounds with the transition metals  

E-print Network

173 Valence state of cerium in the hexagonal CeM5 compounds with the transition metals D. Gignoux effets du champ cristallin sur l'ion Ce3+. Au contraire, la susceptibilité de CeNi5 est d'un ordre de. Abstract. 2014 The valence state of cerium in CeCo5, CeNi5, CeCu5 and the pseudo-binary Ce(Ni1-xCux)5

Boyer, Edmond

386

Schizophrenia patients' perceptual biases in response to positively and negatively valenced emotion chimeras  

Microsoft Academic Search

Background. In a prior study, we observed that schizophrenia patients display atypical perceptual biases in response to emotional (happy}neutral) facial chimeras. Methods. The present study was an attempt to replicate and extend those findings, using emotional stimuli with negative aective valence (angry}neutral chimeras) as well as positive valence, and including more than one type of non-aective facial comparison task. We

DIANE C. GOODING; KATHLEEN A. TALLENT

2002-01-01

387

Valence band structure of the icosahedral Ag-In-Yb quasicrystal  

Microsoft Academic Search

The valence band structure of the icosahedral (i) Ag-In-Yb quasicrystal, which is isostructural to the binary i-Cd-Yb system, is investigated by ultraviolet photoemission spectroscopy (UPS). Experimental results are compared with electronic-structure calculations of a cubic approximant of the same phase. UPS spectra from the fivefold, threefold, and twofold i-Ag-In-Yb surfaces reveal that the valence band near to the Fermi level

H. R. Sharma; G. Simutis; V. R. Dhanak; P. J. Nugent; C. Cui; M. Shimoda; R. McGrath; A. P. Tsai; Y. Ishii

2010-01-01

388

Valence, arousal, and task effects in emotional prosody processing.  

PubMed

Previous research suggests that emotional prosody processing is a highly rapid and complex process. In particular, it has been shown that different basic emotions can be differentiated in an early event-related brain potential (ERP) component, the P200. Often, the P200 is followed by later long lasting ERPs such as the late positive complex. The current experiment set out to explore in how far emotionality and arousal can modulate these previously reported ERP components. In addition, we also investigated the influence of task demands (implicit vs. explicit evaluation of stimuli). Participants listened to pseudo-sentences (sentences with no lexical content) spoken in six different emotions or in a neutral tone of voice while they either rated the arousal level of the speaker or their own arousal level. Results confirm that different emotional intonations can first be differentiated in the P200 component, reflecting a first emotional encoding of the stimulus possibly including a valence tagging process. A marginal significant arousal effect was also found in this time-window with high arousing stimuli eliciting a stronger P200 than low arousing stimuli. The P200 component was followed by a long lasting positive ERP between 400 and 750 ms. In this late time-window, both emotion and arousal effects were found. No effects of task were observed in either time-window. Taken together, results suggest that emotion relevant details are robustly decoded during early processing and late processing stages while arousal information is only reliably taken into consideration at a later stage of processing. PMID:23801973

Paulmann, Silke; Bleichner, Martin; Kotz, Sonja A

2013-01-01

389

Valence, arousal, and task effects in emotional prosody processing  

PubMed Central

Previous research suggests that emotional prosody processing is a highly rapid and complex process. In particular, it has been shown that different basic emotions can be differentiated in an early event-related brain potential (ERP) component, the P200. Often, the P200 is followed by later long lasting ERPs such as the late positive complex. The current experiment set out to explore in how far emotionality and arousal can modulate these previously reported ERP components. In addition, we also investigated the influence of task demands (implicit vs. explicit evaluation of stimuli). Participants listened to pseudo-sentences (sentences with no lexical content) spoken in six different emotions or in a neutral tone of voice while they either rated the arousal level of the speaker or their own arousal level. Results confirm that different emotional intonations can first be differentiated in the P200 component, reflecting a first emotional encoding of the stimulus possibly including a valence tagging process. A marginal significant arousal effect was also found in this time-window with high arousing stimuli eliciting a stronger P200 than low arousing stimuli. The P200 component was followed by a long lasting positive ERP between 400 and 750 ms. In this late time-window, both emotion and arousal effects were found. No effects of task were observed in either time-window. Taken together, results suggest that emotion relevant details are robustly decoded during early processing and late processing stages while arousal information is only reliably taken into consideration at a later stage of processing. PMID:23801973

Paulmann, Silke; Bleichner, Martin; Kotz, Sonja A.

2013-01-01

390

Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update  

NASA Technical Reports Server (NTRS)

We have been developing an oxygen barometer based on the valence state of V (V(2+), V(3+), V(4+), and V(5+)) in solar system basaltic glasses. The V valence is determined by synchrotron micro x-ray absorption near edge structure (XANES), which uses x-ray absorption associated with core-electronic transitions (absorption edges) to reveal a pre-edge peak whose intensity is directly proportional to the valence state of an element. XANES has advantages over other techniques that determine elemental valence because measurements can be made non-destructively in air and in situ on conventional thin sections at a micrometer spatial resolution with elemental sensitivities of approx. 100 ppm. Recent results show that fO2 values derived from the V valence technique are consistent with fO2 estimates determined by other techniques for materials that crystallized above the IW buffer. The fO2's determined by V valence (IW-3.8 to IW-2) for the lunar pyroclastic glasses, however, are on the order of 1 to 2.8 log units below previous estimates. Furthermore, the calculated fO2's decrease with increasing TiO2 contents from the A17 VLT to the A17 Orange glasses. In order to investigate these results further, we have synthesized lunar green and orange glasses and examined them by XANES.

Karner, J. M.; Sutton, S. R.; Papike, J. J.; Shearer, C. K.; Jones, J. H.; Newville, M.

2004-01-01

391

Light-scattering detection of quantum phases of ultracold atoms in optical lattices  

SciTech Connect

Ultracold atoms loaded on optical lattices can provide unprecedented experimental systems for the quantum simulations and manipulations of many quantum phases. However, so far, how to detect these quantum phases effectively remains an outstanding challenge. Here, we show that the optical Bragg scattering of cold atoms loaded on optical lattices can be used to detect many quantum phases, which include not only the conventional superfluid and Mott insulating phases, but also other important phases, such as various kinds of charge density wave (CDW), valence bond solid (VBS), CDW supersolid (CDW-SS) and Valence bond supersolid (VB-SS).

Ye Jinwu [Department of Physics, Capital Normal University, 100048 Beijing (China); Department of Physics and Astronomy, Mississippi State University, P. O. Box 5167, Mississippi State, MS, 39762 (United States); Zhang, J. M.; Liu, W. M. [Institute of Physics, Chinese Academy of Sciences, 100080 Beijing (China); Zhang Keye; Li Yan; Zhang Weiping [Department of Physics, East China Normal University, 200062 Shanghai (China)

2011-05-15

392

Solder extrusion pressure bonding process and bonded products produced thereby  

DOEpatents

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

Beavis, Leonard C. (Albuquerque, NM); Karnowsky, Maurice M. (Albuquerque, NM); Yost, Frederick G. (Ceder Crest, NM)

1992-01-01

393

Bond Dissociation Energies in Second-Row Compounds  

SciTech Connect

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Heats of formation at 0 and 298 K are predicted for PF?, PF?, PF?O, SF?, SF?, SF?, SF?O, SF?O?, and SF?O as well as a number of radicals derived from these stable compounds on the basis of coupled cluster theory [CCSD(T)] calculations extrapolated to the complete basis set limit. In order to achieve near chemical accuracy (±1 kcal/mol), additional corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, a correction for first-order atomic spin-orbit effects, and vibrational zero-point energies. The calculated values substantially reduce the error limits for these species. A detailed comparison of adiabatic and diabatic bond dissociation energies (BDEs) is made and used to explain trends in the BDEs. Because the adiabatic BDEs of polyatomic molecules represent not only the energy required for breaking a specific bond but also contain any reorganization energies of the bonds in the resulting products, these BDEs can be quite different for each step in the stepwise loss of ligands in binary compounds. For example, the adiabatic BDE for the removal of one fluorine ligand from the very stable closed-shell SF? molecule to give the unstable SF? radical is 2.8 times the BDE needed for the removal of one fluorine ligand from the unstable SF? radical to give the stable closed-shell SF? molecule. Similarly, the BDE for the removal of one fluorine ligand from the stable closed-shell PF?O molecule to give the unstable PF?O radical is higher than the BDE needed to remove the oxygen atom to give the stable closed-shell PF? molecule. The same principles govern the BDEs of the phosphorus fluorides and the sulfur oxofluorides. In polyatomic molecules, care must be exercised not to equate BDEs with the bond strengths of given bonds. The measurement of the bond strength or stiffness of a given bond represented by its force constant involves only a small displacement of the atoms near equilibrium and, therefore, does not involve any reorganization energies, i.e., it may be more appropriate to correlate with the diabatic product states.

Grant, Daniel J.; Matus, Myrna H.; Switzer, Jackson R.; Dixon, David A.; Francisco, Joseph S.; Christe, Karl O.

2008-04-10

394

Electron densities for the outer valence orbitals of pyridine: comparison of EMS measurements with near Hartree Fock limit and density functional theory calculations  

NASA Astrophysics Data System (ADS)

Momentum distributions of the outer valence orbitals of the aromatic molecule pyridine (C 5H 5N), measured by electron momentum spectroscopy (EMS), are compared with Hartree-Fock (HF) and density functional theory (DFT) calculations. The experiment was performed using a multichannel EMS spectrometer at a total energy of 1200 eV plus the binding energy and in symmetric non-coplanar kinematics. Binding energy spectra have been measured in the energy range of 4-45 eV at the azimuthal angles ?=0° and ?=8°, and in the range of 4-24 eV over a range of azimuthal angles from 0° to ±30°. Theoretical momentum profiles are calculated in the plane wave impulse approximation using the target HF approximation, and also with DFT using the target Kohn-Sham approximation with the B3LYP and B3PW91 gradient corrected functionals. Basis sets range from STO-3G to aug-cc-pVQZ. The shapes of the experimental momentum profiles, and thus the frontier orbital electron behaviour, are generally quite well reproduced by both the HF and the DFT calculations of the delocalised (canonical) molecular orbitals when using the larger diffuse basis sets. It is also found that the calculated localised molecular orbitals (i.e. valence bond hybrid orbitals involving resonance forms) completely fail to describe the frontier orbital electron behaviour observed in the EMS experiments for pyridine.

Tixier, S.; Shapley, W. A.; Zheng, Y.; Chong, D. P.; Brion, C. E.; Shi, Z.; Wolfe, Saul

2001-08-01

395

Bond Sensitivity to Silicone Contamination  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

396

Better Bonded Ethernet Load Balancing  

SciTech Connect

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

Gabler, Jason

2006-09-29

397

Silicene Nano-Ribbons: Strong Resistance Towards Oxidation due to sp^2 Hybridization of the Si Valence Orbitals  

NASA Astrophysics Data System (ADS)

We have synthesized for the first time silicene, that is, a new silicon allotrope analogous to graphene recently theoretically predicted [1], in the form of a massively parallel array of quantized zigzag nano-ribbons with a common "magic" width of 1.6 nm. They display characteristic linear band dispersions similar to the Dirac cones of graphene, in correspondence with their hexagonal arrangement seen in STM imaging [2]. Here we show, through the angle-dependence of REEL spectra taken at the Si L2,3 edge, the typical signatures of 2p -> ?* and 2p -> ?* transitions associated with sp^2 hybridization of the Si valence orbitals. We further show through high-resolution synchrotron radiation Si 2p core-level spectroscopy measurements that the afore mentioned silicene grating is very resistant toward oxidation. Typically, the oxygen uptake starts at about 10^4 higher doses than on the clean Si(111)7x7 surface. Indeed, this striking behavior is directly related to the sp^2 bonding, an additional confirmation of the silicene (i.e., graphene-like) nature of the nano-ribbons. [4pt] [1] S. Cahangorov et al., Phys. Rev. Lett., 102, 236804 (2009). [0pt] [2] P. De Padova et al., Appl. Phys. Lett. 96, 261905 (2010).

Le Lay, Guy; de Padova, Paola; Quaresima, Claudio; Olivieri, Bruno; Perfetti, Paolo

2011-03-01

398

Mixed valence in YBaFe(2)O(5).  

PubMed

YBaFe(2)O(5) has been synthesized by heating a nanoscale citrate precursor in a carefully controlled reducing environment. Successful synthesis of a single-phase sample can only be achieved in a narrow window of oxygen partial pressures and temperatures. YBaFe(2)O(5) adopts an oxygen-deficient perovskite-type structure, which contains double layers of corner sharing FeO(5) square pyramids separated by Y(3+) ions. At T(N) congruent with 430 K, tetragonal (P4/mmm) and paramagnetic YBaFe(2)O(5) orders antiferromagnetically (AFM) experiencing a slight orthorhombic distortion (Pmmm). Around this temperature, it can be characterized as a class-III mixed valence (MV) compound, where all iron atoms exist as equivalent MV Fe(2.5+) ions. The magnetic structure is characterized by AFM Fe-O-Fe superexchange coupling within the double layers and a ferromagnetic Fe-Fe direct-exchange coupling between neighboring double layers. Upon cooling below approximately 335 K, a premonitory charge ordering (2Fe(2.5+) --> Fe(2.5+delta) + Fe(2.5)(-delta)) into a class-II MV phase takes place. This transition is detected by differential scanning calorimetry, but powder diffraction techniques fail to detect any volume change or a long-range structural order. At approximately 308 K, a complete charge ordering (2Fe(2.5+) --> Fe(2+) + Fe(3+)) into a class-I MV compound takes place. This charge localization triggers a number of changes in the crystal, magnetic, and electronic structure of YBaFe(2)O(5). The magnetic structure rearranges to a G-type AFM structure, where both the Fe-O-Fe superexchange and the Fe-Fe direct-exchange couplings are antiferromagnetic. The crystal structure rearranges (Pmma) to accommodate alternating chains of Fe(2+) and Fe(3+) running along b and an unexpectedly large cooperative Jahn-Teller distortion about the high-spin Fe(2+) ions. This order of charges does not fulfill the Anderson condition, and it rather corresponds to an ordering of doubly occupied Fe(2+) d(xz) orbitals. Comparisons with YBaMn(2)O(5) and YBaCo(2)O(5) are made to highlight the impact of changing the d-electron count. PMID:12588147

Woodward, Patrick M; Karen, Pavel

2003-02-24

399

Anion Transport with Halogen Bonds.  

PubMed

This review covers the application of halogen bonds to transport anions across lipid bilayer membranes. The introduction provides a brief description of biological and synthetic transport systems. Emphasis is on examples that explore interactions beyond the coordination with lone pairs or hydrogen bonds for the recognition of cations and anions, particularly cation-? and anion-? interactions, and on structural motifs that are relevant for transport studies with halogen bonds. Section 2 summarizes the use of macrocyclic scaffolds to achieve transport with halogen bonds, focusing on cyclic arrays of halogen-bond donors of different strengths on top of calixarene scaffolds. This section also introduces methods to study anion binding in solution and anion transport in fluorogenic vesicles. In Sect. 3, transport studies with monomeric halogen bond-donors are summarized. This includes the smallest possible organic anion transporter, trifluoroiodomethane, a gas that can be bubbled through a suspension of vesicles to turn on transport. Anion transport with a gas nicely illustrates the power of halogen bonds for anion transport. Like hydrogen bonds, they are directional and strong, but compared to hydrogen-bond donors, halogen-bond donors are more lipophilic. Section 3 also offers a concise introduction to the measurement of ion selectivity in fluorogenic vesicles and conductance experiments in planar bilayer membranes. Section 4 introduces the formal unrolling of cyclic scaffolds into linear scaffolds that can span lipid bilayers. As privileged transmembrane scaffolds, the importance of hydrophobically matching fluorescent p-oligophenyl rods is fully confirmed. The first formal synthetic ion channel that operates by cooperative multiion hopping along transmembrane halogen-bonding cascades is described. Compared to homologs for anion-? interactions, transport with halogen bonds is clearly more powerful. PMID:24696354

Jentzsch, Andreas Vargas; Matile, Stefan

2014-04-01

400

Pauling bond strength, bond length and electron density distribution  

NASA Astrophysics Data System (ADS)

The power law regression equation, = 1.46(/r)-0.19, relating the average experimental bond lengths, , to the average accumulation of the electron density at the bond critical point, , between bonded pairs of metal and oxygen atoms (r is the row number of the M atom), determined at ambient conditions for oxide crystals, is similar to the regression equation R(M-O) = 1.41(?( r c)/r)-0.21 determined for three perovskite crystals at pressures as high as 80 GPa. The pair are also comparable with the equation = 1.43(/r)-0.21 determined for oxide crystals at ambient conditions and = 1.39(/r)-0.22 determined for geometry-optimized hydroxyacid molecules that relate the geometry-optimized bond lengths to the average Pauling bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the equations relating and with bond length, it seems plausible that the Pauling bond strength might serve a rough estimate of the accumulation of the electron density between M-O bonded pairs of atoms. Similar expressions, relating bond length and bond strength hold for fluoride, nitride and sulfide molecules and crystals. The similarity of the expressions for the crystals and molecules is compelling evidence that molecular and crystalline M-O bonded interactions are intrinsically related. The value of = r[(1.41)/]4.76 determined for the average bond length for a given coordination polyhedron closely matches the Pauling's electrostatic bond strength reaching each the coordinating anions of the coordinated polyhedron. Despite the relative simplicity of the expression, it appears to be more general in its application in that it holds for the bulk of the M-O bonded pairs of atoms of the periodic table.

Gibbs, G. V.; Ross, N. L.; Cox, D. F.; Rosso, K. M.; Iversen, B. B.; Spackman, M. A.

2014-01-01

401

Independent structural and valence state transitions in the cation-ordered double perovskites Ba{sub 2-x}Sr{sub x}TbIrO{sub 6}  

SciTech Connect

Synchrotron X-ray and neutron powder diffraction were used to investigate the formation, structure and bonding in the double perovskite Ba{sub 2-x}Sr{sub x}TbIrO{sub 6} solid solutions. The results showed that these oxides all exhibit ordering of the Tb and Ir cations in a double perovskite-type structure. Three distinct structural types differing in symmetry and/or valence states were formed depending on the precise Ba:Sr ratio on the perovskite A site; x=<0.3 cubic (Fm3-bar m) with Tb{sup 4+} and Ir{sup 4+}; 0.4==1.2 monoclinic (P2{sub 1}/n) with Tb{sup 3+} and Ir{sup 5+}. The transitions between these appear to be first order in nature.

Zhou Qingdi [Centre for Structural Biology and Chemistry, School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia); Kennedy, Brendan J. [Centre for Structural Biology and Chemistry, School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia)]. E-mail: kennedyb@chem.usyd.edu.au

2005-11-15

402

Bond strengths of ceramic brackets using different bonding techniques.  

PubMed

A series of laboratory investigations was carried out to compare the shear-type bond strengths and site of bond failure of ceramic orthodontic brackets bonded to etched enamel. When light-cured composite resin was used as the luting agent, there was no reduction in bond strength when using 2.5 per cent nitric acid to etch the enamel, compared to 37 per cent phosphoric acid. The use of the two resin modified glass ionomer cements were found to give rise to significantly lower bond strengths than composite resin when used for placing ceramic brackets. Significantly less composite resin remained on the enamel surface following bracket removal in those samples etched with nitric acid. PMID:7786864

Blight, S J; Lynch, E

1995-02-01

403

Nature of one-dimensional short hydrogen bonding: bond distances, bond energies, and solvent effects.  

PubMed

On the basis of recently synthesized calix[4]hydroquinone (CHQ) nanotubes which were self-assembled with infinitely long one-dimensional (1-D) short hydrogen bonds (SHB), we have investigated the nature of 1-D SHB using first-principles calculations for all the systems including the solvent water. The H-bonds relay (i.e., contiguous H-bonds) effect in CHQs shortens the H...O bond distances significantly (by more than 0.2 A) and increases the bond dissociation energy to a large extent (by more than approximately 4 kcal/mol) due to the highly enhanced polarization effect along the H-bond relay chain. The H-bonds relay effect shows a large increase in the chemical shift associated with the SHB. The average binding energies for the infinite 1-D H-bond arrays of dioles and dions increase by approximately 4 and approximately 9 kcal/mol per H-bond, respectively. The solvent effect (due to nonbridging water molecules) has been studied by explicitly adding water molecules in the CHQ tube crystals. This effect is found to be small with slight weakening of the SHB strength; the H...O bond distance increases only by 0.02 A, and the average binding energy decreases by approximately 1 kcal/mol per H-bond. All these results based on the first-principles calculations are the first detailed analysis of energy gain by SHB and energy loss by solvent effect, based on a partitioning scheme of the interaction energy components. These reliable results elucidate not only the self-assembly phenomena based on the H-bond relay but also the solvent effect on the SHB strength. PMID:14971954

Suh, Seung Bum; Kim, Jong Chan; Choi, Young Cheol; Yun, Sunggoo; Kim, Kwang S

2004-02-25

404

Molecular core-valence correlation effects involving the post-d elements Ga-Rn: Benchmarks and new pseudopotential-based correlation consistent basis sets  

NASA Astrophysics Data System (ADS)

Correlation consistent basis sets that are suitable for the correlation of the outer-core (n -1)spd electrons of the post-d elements Ga-Rn have been developed. These new sets, denoted by cc-pwCVXZ-PP (X=D,T,Q,5), are based on the previously reported cc-pVXZ-PP sets that were built in conjunction with accurate small-core relativistic pseudopotentials (PPs) and designed only for valence nsp correlation. These new basis sets have been utilized in benchmark coupled cluster calculations of the core-valence correlation effects on the dissociation energies and spectroscopic properties of several small molecules. As expected, the most important contribution is the correlation of the (n -1)d electrons. For example, in the case of the group 13 homonuclear diatomics (Ga2,In2,Tl2), this leads to a dissociation energy increase compared to a valence-only treatment from 1.5 to 3.2 kcal/mol, bond length shortenings from -0.076 to -0.125 Å, and harmonic frequency increases of 7-8 cm-1. Even in the group 15 cases (As2,Sb2,Bi2), the analogous effects of (n-1)d electron correlation are certainly not insignificant, the largest values being +4.4 kcal/mol, -0.049 Å, and +9.6 cm-1 for the effects on De, re, and ?e, respectively. In general, the effects increase in magnitude down a group from 4p to 6p. Correlation of the outer-core (n -1)p electrons is about an order of magnitude less important than (n -1)d but larger than that of the (n -1)s. The effect of additional tight functions for Hartree-Fock and valence sp correlation was found to be surprisingly large, especially for the post-4d and post-5d elements. The pseudopotential results for the molecules containing post-3d elements are also compared to the analogous all-electron calculations employing the Douglas-Kroll-Hess Hamiltonian. The errors attributed to the PP approximation are found to be very small.

Peterson, Kirk A.; Yousaf, Kazim E.

2010-11-01

405

Determination of the valence band structure of an alkali phosphorus oxynitride glass: A synchrotron XPS study on LiPON  

NASA Astrophysics Data System (ADS)

Lithium phosphorus oxynitride (LiPON) is a solid state electrolyte commonly used in thin film batteries (TFBs). Advanced TFBs face the issue of detrimental electrode-electrolyte interlayer formation, related to the electronic structure of the interface. In this contribution, we study the valence band structure of LiPON using resonant photoemission and synchrotron photoemission with variable excitation energies. The identification of different valence band features is done according to the known valence band features of meta- and orthophosphates. Additionally we compare our results with partial density of states simulations from literature. We find that the valence band structure is similar to the known metaphosphates with an additional contribution of nitrogen states at the top of the valence band. From the results we conclude that synchrotron X-ray photoemission (XPS) is a useful tool to study the valence band structure of nitridated alkali phosphate glasses.

Schwöbel, André; Precht, Ruben; Motzko, Markus; Carrillo Solano, Mercedes A.; Calvet, Wolfram; Hausbrand, René; Jaegermann, Wolfram

2014-12-01

406

Valence-band discontinuity between GaN and AlN measured by x-ray photoemission spectroscopy  

SciTech Connect

The valence-band discontinuity at a wurtzite GaN/AlN(0001) heterojunction is measured by x-ray photoemission spectroscopy. The method first measures the core level binding energies with respect to the valence-band maximum in both GaN and AlN bulk films. The precise location of the valence-band maximum is determined by aligning prominent features in the valence-band spectrum with calculated densities of states. Tables of core level binding energies relative to the valence-band maximum are reported for both GaN and AlN. Subsequent measurements of separations between Ga and Al core levels for thin overlayers of GaN film grown on AlN and vice versa yield a valence-band discontinuity of [Delta][ital E][sub [ital V

Martin, G.; Strite, S.; Botchkarev, A.; Agarwal, A.; Rockett, A.; Morkoc, H. (University of Illinois at Urbana-Champaign, Materials Research Laboratory, 104 South Goodwin Avenue, Urbana, Illinois 61801 (United States)); Lambrecht, W.R.L.; Segall, B. (Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7090 (United States))

1994-08-01

407

Experimental Constraints on the Partitioning and Valence of V and Cr in Garnet and Coexisting Glass  

NASA Technical Reports Server (NTRS)

A series of experiments with garnet and coexisting melt have been carried out across a range of oxygen fugacities (near hematite-magnetite (HM) to below the iron-wustite (IW) buffers) at 1.7 GPa to study the partitioning and valence of Cr and V in both phases. Experiments were carried out in a non end loaded piston cylinder apparatus, and the run products were analyzed with electron microprobe and xray absorption near edge structure (XANES) analysis at beamline 13-ID at the Advanced Photon Source of Argonne National Lab. The valence of vanadium and chromium were determined using the position and intensity of the Ka pre-edge peaks, calibrated on a series of Cr and Vbearing standard glasses. This technique has been applied to V and Cr in glasses and V in spinels previously, and in these isotropic phases there are no orientational effects on the XANES spectra (Righter et al., 2006, Amer. Mineral. 91, 1643-1656). We also now demonstrate this to be true for V and Cr in garnet. Also, previous work has shown that V has a higher valence in the glass (or melt) than in the coexisting spinel. This is also true for V in garnet-glass pairs in this study. Vanadium valence in garnets varies from 2.7 below the IW buffer to 3.7 near HM, and for coexisting glass it varies from 3.2 to 4.3. Vanadium valence measured in some natural garnets from mantle localities indicates V in the more reduced range at 2.5. Comparisons will be made between fO2 estimated from V valence and other methods for garnet-bearing mantle samples. In contrast, Cr valence measured in garnet and coexisting glass for all experimental and natural samples is 2.9- 3.0, suggesting that the valence of Cr does not vary within either phase across a large fO2 range. These results demonstrate that while V varies from 2+ to 3+ to 4+ in garnet-melt systems, Cr does not, and this will ultimately affect the partitioning behavior of these two elements in natural systems. Garnet/melt D(Cr) are between 12 and 17 across this range of fO2, whereas D(V) has the highest partition coefficient approx.3, near the IW buffer where the valence of V is almost entirely 3+.

Righter, K.; Sutton, S.; Berthet, S.; Newville, M.

2008-01-01

408

Study of two-spin entanglement in singlet states  

NASA Astrophysics Data System (ADS)

We study the entanglement properties of two-spin subsystems in spin-singlet states. The average entanglement between two spins is maximized in a single valence-bond (VB) state. On the other hand, Ev2 (the average entanglement between a subsystem of two spins and the rest of the system) can be maximized through a homogenized superposition of the VB states. The maximal Ev2 rapidly increases with system size and saturates at its maximum allowed value. We adopt two ways of obtaining maximal Ev2 states: (1) imposing homogeneity on singlet states; and (2) generating isotropy in a general homogeneous state. By using these two approaches, we construct explicitly four-spin and six-spin highly entangled states that are both isotropic and homogeneous. Our maximal E2v states represent a new class of resonating-valence-bond states which we show to be the ground states of the infinite-range Heisenberg model.

Lone, M. Q.; Dey, A.; Yarlagadda, S.

2015-01-01

409

Time-resolved imaging of purely valence-electron dynamics during a chemical reaction  

NASA Astrophysics Data System (ADS)

Chemical reactions are manifestations of the dynamics of molecular valence electrons and their couplings to atomic motions. Emerging methods in attosecond science can probe purely electronic dynamics in atomic and molecular systems. By contrast, time-resolved structural-dynamics methods such as electron or X-ray diffraction and X-ray absorption yield complementary information about the atomic motions. Time-resolved methods that are directly sensitive to both valence-electron dynamics and atomic motions include photoelectron spectroscopy and high-harmonic generation: in both cases, this sensitivity derives from the ionization-matrix element. Here we demonstrate a time-resolved molecular-frame photoelectron-angular-distribution (TRMFPAD) method for imaging the purely valence-electron dynamics during a chemical reaction. Specifically, the TRMFPADs measured during the non-adiabatic photodissociation of carbon disulphide demonstrate how the purely electronic rearrangements of the valence electrons can be projected from inherently coupled electronic-vibrational dynamics. Combined with ongoing efforts in molecular frame alignment and orientation, TRMFPADs offer the promise of directly imaging valence-electron dynamics during molecular processes without involving the use of strong, highly perturbing laser fields.

Hockett, Paul; Bisgaard, Christer Z.; Clarkin, Owen J.; Stolow, Albert

2011-08-01

410

Amygdala responses to Valence and its interaction by arousal revealed by MEG.  

PubMed

It is widely accepted that the amygdala plays a crucial role in the processing of emotions. The precise nature of its involvement is however unclear. We hypothesized that ambivalent findings from neuroimaging studies that report amygdala's activity in emotions, are due to distinct functional specificity of amygdala's sub-divisions and specifically to differential reactivity to arousal and valence. The goal of the present study is to characterize the amygdala response to affective stimuli by disentangling the contributions of arousal and valence. Our hypothesis was prompted by recent reports claiming anatomical sub-divisions of amygdala based on cytoarchitecture and the functional maps obtained from diverse behavioral, emotional, and physiological stimulation. We measured magnetoencephalography (MEG) recordings from 12 healthy individuals passively exposed to affective stimuli from the International Affective Picture System (IAPS) collection using a 2 (Valence levels)× 2 (Arousal levels) design. Source power was estimated using a beamformer technique with the activations referring to the amygdala sub-divisions defined through probabilistic cytoarchitectonic maps. Right laterobasal amygdala activity was found to mediate negative valence (elicited by unpleasant stimuli) while left centromedial activity was characterized by an interaction of valence by arousal (arousing pleasant stimuli). We did not find a main effect for amygdala activations in any of its sub-divisions for arousal modulation. To the best of our knowledge, our findings from non-invasive MEG data indicate for the first time, a distinct functional specificity of amygdala anatomical sub-divisions in the emotional processing. PMID:23688672

Styliadis, Charalampos; Ioannides, Andreas A; Bamidis, Panagiotis D; Papadelis, Christos

2014-07-01

411

Pain predictability reverses valence ratings of a relief-associated stimulus  

PubMed Central

Relief from pain is positively valenced and entails reward-like properties. Notably, stimuli that became associated with pain relief elicit reward-like implicit responses too, but are explicitly evaluated by humans as aversive. Since the unpredictability of pain makes pain more aversive, this study examined the hypotheses that the predictability of pain also modulates the valence of relief-associated stimuli. In two studies, we presented one conditioned stimulus (FORWARDCS+) before a painful unconditioned stimulus (US), another stimulus (BACKWARDCS+) after the painful US, and a third stimulus (CS?) was never associated with the US. In Study 1, FORWARDCS+ predicted half of the USs while the other half was delivered unwarned and followed by BACKWARDCS+. In Study 2, all USs were predicted by FORWARDCS+ and followed by BACKWARDCS+. In Study 1 both FORWARDCS+ and BACKWARDCS+ were rated as negatively valenced and high arousing after conditioning, while BACKWARDCS+ in Study 2 acquired positive valence and low arousal. Startle amplitude was significantly attenuated to BACKWARDCS+ compared to FORWARDCS+ in Study 2, but did not differ among CSs in Study 1. In summary, predictability of aversive events reverses the explicit valence of a relief-associated stimulus. PMID:24068989

Andreatta, Marta; Mühlberger, Andreas; Glotzbach-Schoon, Evelyn; Pauli, Paul

2013-01-01

412

Looking behaviour and preference for artworks: the role of emotional valence and location.  

PubMed

The position of an item influences its evaluation, with research consistently finding that items occupying central locations are preferred and have a higher subjective value. The current study investigated whether this centre-stage effect (CSE) is a result of bottom-up gaze allocation to the central item, and whether it is affected by item valence. Participants (n=50) were presented with three images of artistic paintings in a row and asked to choose the image they preferred. Eye movements were recorded for a subset of participants (n=22). On each trial the three artworks were either similar but different, or were identical and with positive valence, or were identical and with negative valence. The results showed a centre-stage effect, with artworks in the centre of the row preferred, but only when they were identical and of positive valence. Significantly greater gaze allocation to the central and left artwork was not mirrored by equivalent increases in preference choices. Regression analyses showed that when the artworks were positive and identical the participants' last fixation predicted preference for the central art-work, whereas the fixation duration predicted preference if the images were different. Overall the result showed that item valence, rather than level of gaze allocation, influences the CSE, which is incompatible with the bottom-up gaze explanation. We propose that the centre stage heuristic, which specifies that the best items are in the middle, is able to explain these findings and the centre-stage effect. PMID:25203454

Kreplin, Ute; Thoma, Volker; Rodway, Paul

2014-10-01

413

Representational similarity of social and valence information in the medial pFC.  

PubMed

The human brain is remarkably adept at integrating complex information to form unified psychological representations of agents, objects, and events in the environment. Two domains in which this ability is particularly salient are the processing of social and valence information and are supported by common cortical areas in the medial pFC (MPFC). Because social information is often embedded within valenced emotional contexts, it is possible that activation patterns within the MPFC may represent both of these types of cognitive processes when presented simultaneously. The current study tested this possibility by employing a large-scale automated meta-analysis tool, together with multivoxel pattern analysis to investigate the representational similarity of social and valence information in the MPFC during fMRI. Using a representational similarity analysis, we found a high degree of representational similarity both within social dimensions and within valence dimensions, but not across them (e.g., positive social information was highly dissimilar to negative nonsocial information), in a ventral portion of the MPFC. These results were significantly correlated with a behaviorally measured similarity structure of the same stimuli, suggesting that a psychologically meaningful representation of social and valence information is reflected by multivoxel activation patterns in the ventral MPFC. PMID:25100218

Chavez, Robert S; Heatherton, Todd F

2015-01-01

414

Too close for comfort: Stimulus valence moderates the influence of motivational orientation on distance perception.  

PubMed

The relationship between approach and avoidance motivational orientations and valenced stimuli has previously been discussed in relation to physical distance. However, it has remained unclear whether approach and avoidance can actually change how people perceive the physical distance to valenced stimuli. Drawing on research on motivational orientation and valence as well as the motivated perception account, we predicted that valenced stimuli incompatible with motivational orientation would be perceived as closer than compatible stimuli because they motivate the goal of resolving the inconsistency arising from discrepant affective information. This prediction was supported in a series of 4 experiments. Findings were consistent across different manipulations of motivational orientation, including motor movements (Experiments 1 and 2) and cognitive procedures (Experiments 3 and 4), and across different types of stimuli, including abstract words (Experiments 1, 2, and 4) and photos of concrete objects (Experiment 3). Experiment 4 further investigated the mechanism behind the influence of incompatibility versus compatibility between motivational orientation and valence on distance perception. The findings showed that, relative to compatibility, incompatibility resulted in participants solving more anagrams, presumably because the goal-related motivational state gave rise to a general state of activation. Furthermore, perceptual estimates were correlated with the activity of the Behavioral Inhibition System (BIS) and the activity of the Behavioral Activation System (BAS) relative to the BIS, further suggesting that goal-related motivation may be associated with perception. Overall, the present research adds to a growing body of evidence suggesting that visual perception is shaped by motivational considerations. PMID:25437132

Krpan, Dario; Schnall, Simone

2014-12-01

415

On integrable matrix product operators with bond dimension D = 4  

NASA Astrophysics Data System (ADS)

We construct and study a two-parameter family of matrix product operators of bond dimension D = 4. The operators M(x, y) act on ({\\Bbb{C}}_2)\\otimes N , i.e. the space of states of a spin-1/2 chain of length N. For the particular values of the parameters: x = 1/3 and y=1/\\sqrt{3} , the operator turns out to be proportional to the square root of the reduced density matrix of the valence-bond-solid state on a hexagonal ladder. We show that M(x, y) has several interesting properties when (x, y) lies on the unit circle centered at the origin: x2 + y2 = 1. In this case, we find that M(x, y) commutes with the Hamiltonian and all the conserved charges of the isotropic spin-1/2 Heisenberg chain. Moreover, M(x1, y1) and M(x2, y2) are mutually commuting if x^2i + y^2_i=1 for both i = 1 and 2. These remarkable properties of M(x, y) are proved as a consequence of the Yang–Baxter equation.

Katsura, Hosho

2015-01-01

416

Microwave bonding of MEMS component  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

417

Computational Chemistry of Adhesive Bonds  

NASA Technical Reports Server (NTRS)

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

Phillips, Donald H.

1999-01-01

418

Ultrasonic phosphate bonding of nanoparticles.  

PubMed

Low intensity ultrasound-induced radicals interact with surface adsorbed orthophosphate to bond nanoparticles with high mechanical strength and surface area. Dissimilar materials could be bonded to form robust metallic, ceramic, and organic composite microparticles. 3D nanostructures of a hydrated and amorphous electrocatalyst with carbon nanotubes were also constructed which exceeded the resistance-limited efficiency of 2D electrodes. PMID:23893468

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

2013-11-01

419

Coulombic Models in Chemical Bonding.  

ERIC Educational Resources Information Center

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

Sacks, Lawrence J.

1986-01-01

420

Weld-bonded titanium structures  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

421

Antisymmetric double exchange in trimeric mixed-valence clusters  

NASA Astrophysics Data System (ADS)

The theory of antisymmetric double exchange (AS DE) interaction is developed for the mixed-valence (MV) trimeric [d n-d n-d n±1 ] clusters of orbitally non-degenerate ions. Strong isotropic double exchange (DE) and Heisenberg exchange interactions (t-J model) form isotropic trigonal states 2S+1?i (? i=A 1, A 2, E) of the MV trimers. Taking into account the spin-orbit coupling results in the vector-type AS DE interaction in these clusters. For the MV trimers with si=1/2, the Hamiltonian of the AS DE coupling has the form H AS DE Z=2 i? ??K ??ZT???(S ?Z-S ?Z) , where K??Z is the antisymmetric ( K?ij=- K?ji) vector parameter of the AS DE interaction and T??? is the isotropic transfer operator. The operator H AS DE Z describes the vector-type spin-transfer interaction induced by the spin-orbit coupling. The microscopic consideration of the AS DE coupling shows that the vector AS DE parameter K?ij is linearly proportional to the spin-orbit coupling constant ? and electron transfer parameter t. The AS DE coupling results in the new effect: the linear AS DE splittings ? of the 2S+1E DE terms, ? are proportional to the cluster AS DE parameter KZ=( KabZ+ KbcZ+ KcaZ)/3. The vector of the AS DE interaction is directed along the trigonal Z-axis: K Z?0, K X=K Y=0 . For the delocalized [d 9-d 10-d 10] ([Cu(II)Cu 2(I)]) cluster, the linear AS DE fine splitting ?=2K Z3 of the ground 2E DE term determines strong anisotropy of the Zeeman splitting, axial anisotropy of g-factors, and magnetic properties. The AS DE coupling mixes the 2S+1A1 and 2S '+1 A2, 2S+1E and 2S '+1 E' DE terms, ? S=0,±1. The mixing of the DE levels 2S+1?i by the AS DE coupling and Dzialoshinsky-Moriya AS exchange (H DM=? ??G???[ S??× S??]) determines the second-order AS contributions {˜[( n1KZ+ n2GZ) 2/( n3t+ n4J)], K Z?G Z, G Z=(G abZ+G bcZ+G caZ)/3} to the cluster zero-field splitting (ZFS) parameters D S( 2S+1?i) of the axial anisotropy ( H AN=D S( 2S+1?i)[S z2-S(S+1)/3] , DS? KZ). The second-order AS DE contributions to the ZFS parameters D S( 2S+1?i) are different for the 2S+1A1, 2S+1A2 and 2S+1E DE terms.

Belinsky, Moisey I.

2003-06-01

422

Electronic structure of ?-RbSm(MoO4)2 and chemical bonding in molybdates.  

PubMed

Microcrystals of orthorhombic rubidium samarium molybdate, ?-RbSm(MoO4)2, have been fabricated by solid state synthesis at T = 450 °C, 70 h, and at T = 600 °C, 150 h. The crystal structure has been refined by the Rietveld method in space group Pbcn with cell parameters a = 5.0984(2), b = 18.9742(6) and c = 8.0449(3) Å (RB = 1.72%). Thermal properties of ?-RbSm(MoO4)2 were traced by DSC over the temperature range of T = 20-965 °C, and the earlier reported ? ? ? phase transition at T ? 860-910 °C was not verified. The electronic structure of ?-RbSm(MoO4)2 was studied by employing theoretical calculations and X-ray photoelectron spectroscopy. It has been established that the O 2p-like states contribute mainly to the upper part of the valence band and occupy the valence band maximum, whereas the Mo 4d-like states contribute mainly to the lower part of the valence band. Chemical bonding effects have been analysed from the element core level binding energy data. In addition, it was found that the luminescence spectrum of ?-RbSm(MoO4)2 is rather peculiar among the Sm(3+) containing materials. The optical refractive index dispersion in ?-RbSm(MoO4)2 was also predicted by the first-principles calculations. PMID:25474328

Atuchin, V V; Aleksandrovsky, A S; Chimitova, O D; Diao, Cheng-Peng; Gavrilova, T A; Kesler, V G; Molokeev, M S; Krylov, A S; Bazarov, B G; Bazarova, J G; Lin, Zheshuai

2014-12-01

423

Quantum Confinement in Hydrogen Bond  

E-print Network

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

Santos, Carlos da Silva dos; Ricotta, Regina Maria

2015-01-01

424

?-Hole Bonding: A Physical Interpretation.  

PubMed

The anisotropic electronic densities of covalently-bonded Group IV-VII atoms frequently give rise to regions of positive electrostatic potential on the extensions of single covalent bonds to these atoms. Through such positive "?-holes," the atoms can interact attractively and highly directionally with negative sites such as the lone pairs of Lewis bases, anions, ? electrons, etc. In the case of Group VII this is called "halogen bonding." Hydrogen bonding can be viewed as a less directional subset of ?-hole interactions. Since positive ?-holes often exist in conjunction with regions of negative potential, the atoms can also interact favorably with positive sites. In accordance with the Hellmann-Feynman theorem, all of these interactions are purely Coulombic in nature (which encompasses polarization and dispersion). The strength of ?-hole bonding increases with the magnitudes of the potentials of the positive ?-hole and the negative site; their polarizabilities must sometimes also be taken explicitly into account. PMID:25467532

Politzer, Peter; Murray, Jane S; Clark, Timothy

2014-12-01

425

Anti-electrostatic hydrogen bonds.  

PubMed

Ab?initio and hybrid density functional techniques were employed to characterize a surprising new class of H-bonded complexes between ions of like charge. Representative H-bonded complexes of both anion-anion and cation-cation type exhibit appreciable kinetic stability and the characteristic theoretical, structural, and spectroscopic signatures of hydrogen bonding, despite the powerful opposition of Coulomb electrostatic forces. All such "anti-electrostatic" H-bond (AEHB) species confirm the dominance of resonance-type covalency ("charge transfer") interactions over the inessential (secondary or opposing) "ionic" or "dipole-dipole" forces that are often presumed to be essential for numerical modeling or conceptual explanation of the H-bonding phenomenon. PMID:25196556

Weinhold, Frank; Klein, Roger A

2014-10-13

426

Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study  

NASA Astrophysics Data System (ADS)

Cerium and its technologically relevant compounds are examples of anomalous mixed valency, originating from two competing oxidation states—itinerant Ce4+ and localized Ce3+. Under applied stress, anomalous transitions are observed but not well understood. Here we treat mixed valency as an "alloy" problem involving two valences with competing and numerous site-occupancy configurations. We use density-functional theory with Hubbard U (i.e., DFT+U) to evaluate the effective valence and predict properties, including controlling the valence by pseudoternary alloying. For Ce and its compounds, such as (Ce,La)2(Fe,Co)14B permanent magnets, we find a stable mixed-valent ? state near the spectroscopic value of ?s=3.53. Ce valency in compounds depends on its steric volume and local chemistry. For La doping, Ce valency shifts towards ?-like Ce3+, as expected from steric volume; for Co doping, valency depends on local Ce-site chemistry and steric volume. Our approach captures the key origins of anomalous valency and site-preference chemistry in complex compounds.

Alam, Aftab; Johnson, D. D.

2014-06-01

427

Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study  

SciTech Connect

Cerium and its technologically relevant compounds are examples of anomalous mixed valency, originating from two competing oxidation states—itinerant Ce4+ and localized Ce3+. Under applied stress, anomalous transitions are observed but not well understood. Here we treat mixed valency as an “alloy” problem involving two valences with competing and numerous site-occupancy configurations. We use density-functional theory with Hubbard U (i.e., DFT+U) to evaluate the effective valence and predict properties, including controlling the valence by pseudoternary alloying. For Ce and its compounds, such as (Ce,La)2(Fe,Co)14B permanent magnets, we find a stable mixed-valent ? state near the spectroscopic value of ?s=3.53. Ce valency in compounds depends on its steric volume and local chemistry. For La doping, Ce valency shifts towards ?-like Ce3+, as expected from steric volume; for Co doping, valency depends on local Ce-site chemistry and steric volume. Our approach captures the key origins of anomalous valency and site-preference chemistry in complex compounds.

Alam, Aftab [Ames Laboratory; Johnson, Duane D. [Ames Laboratory

2014-06-01

428

Oregon School Bond Manual. Sixth Edition.  

ERIC Educational Resources Information Center

Given that purchasers of Oregon school bonds rely on recommendations of accredited bond attorneys, this document is designed to assist school districts in complying with state statutes regulating the issuance of school bond issues in order that attorney opinions may be favorable. Six initial steps toward a bond sale and Oregon laws regarding bonds…

Oregon State Dept. of Education, Salem. Office of School District Services.

429

Investigation of surface oxides on aluminum alloys by valence band photoemission  

NASA Astrophysics Data System (ADS)

Core level and valence band x-ray photoelectron spectroscopy are used to study the chemical composition of the surface films on aluminum alloys. Certain alloying elements may preferentially migrate to the surface of an alloy, thereby altering the composition and consequently the chemistry of the surface. The behavior of a 6061 aluminum alloy is compared with that of pure aluminum. It is shown that the type of magnesium film formed at the alloy surface can be determined by comparing the valence band spectra of the aluminum alloy surface with that of known magnesium and aluminum compounds. The experimental valence band spectra of these compounds are supported by spectra generated from band structure calculations. The effect of boiling water on the surface film is discussed, with significant differences in surface chemistry being seen for the metal and the alloy. copyright 2002 American Vacuum Society.

Claycomb, Gregory D.; Sherwood, Peter M. A.

2002-07-01

430

Reactivity of seventeen- and nineteen-valence electron complexes in organometallic chemistry  

NASA Technical Reports Server (NTRS)

A guideline to the reactivity of 17- and 19-valence electron species in organometallic chemistry is proposed which the authors believe will supersede all others. The thesis holds that the reactions of 17-electron metal radicals are associatively activated with reactions proceeding through a 19-valence electron species. The disparate reaction chemistry of the 17-electron metal radicals are unified in terms of this associative reaction pathway, and the intermediacy of 19-valence electron complexes in producing the observed products is discussed. It is suggested that related associatively activated pathways need to be considered in some reactions that are thought to occur by more conventional routes involving 16- and 18-electron intermediates. The basic reaction chemistry and electronic structures of these species are briefly discussed.

Stiegman, Albert E.; Tyler, David R.

1986-01-01

431

Site-selective photoemission from delocalized valence shells induced by molecular rotation.  

PubMed

Due to the generally delocalized nature of molecular valence orbitals, valence-shell spectroscopies do not usually allow to specifically target a selected atom in a molecule. However, in X-ray electron spectroscopy, the photoelectron momentum is large and the recoil angular momentum transferred to the molecule is larger when the photoelectron is ejected from a light atom compared with a heavy one. This confers an extreme sensitivity of the rotational excitation to the ionization site. Here we show that, indeed, the use of high-energy photons to photoionize valence-shell electrons of hydrogen chloride offers an unexpected way to decrypt the atomic composition of the molecular orbitals due to the rotational dependence of the photoionization profiles. The analysis of the site-specific rotational envelopes allows us to disentangle the effects of the two main mechanisms of rotational excitation, based on angular momentum exchange between the molecule and either the incoming photon or the emitted electron. PMID:24809410

Miron, Catalin; Miao, Quan; Nicolas, Christophe; Bozek, John D; Andra?oj?, Witold; Patanen, Minna; Simões, Grazieli; Travnikova, Oksana; Ågren, Hans; Gel'mukhanov, Faris

2014-01-01

432

Reference Valence Effects of Affective S–R Compatibility: Are Visual and Auditory Results Consistent?  

PubMed Central

Humans may be faster to avoid negative words than to approach negative words, and faster to approach positive words than to avoid positive words. That is an example of affective stimulus–response (S–R) compatibility. The present study identified the reference valence effects of affective stimulus–response (S–R) compatibility when auditory stimulus materials are used. The researchers explored the reference valence effects of affective S–R compatibility using a mixed-design experiment based on visual words, visual pictures and audition. The study computed the average compatibility effect size. A t-test based on visual pictures showed that the compatibility effect size was significantly different from zero, t (22)?=?2.43, p<.05 (M?=?485 ms). Smaller compatibility effects existed when switching the presentation mode from visual stimuli to auditory stimuli. This study serves as an important reference for the auditory reference valence effects of affective S–R compatibility. PMID:24743797

Xiaojun, Zhao; Xuqun, You; Changxiu, Shi; Shuoqiu, Gan; Chaoyi, Hu

2014-01-01

433

Improving ethical knowledge and sensemaking from cases through elaborative interrogation and outcome valence.  

PubMed

The case-based approach to learning is popular among many applied fields. However, results of case-based education vary widely on case content and case presentation. This study examined two aspects of case-based education-outcome valence and case elaboration methods-in a two-day case-based Responsible Conduct of Research (RCR) ethics education program. Results suggest that outcome information is an integral part of a quality case. Furthermore, valence consistent outcomes may have certain advantages over mixed valence outcome information. Finally, students enjoy and excel working with case material, and the use of elaborative interrogation techniques can significantly improve internally-focused ethical sensemaking strategies associated with personal biases, constraints, and emotions. PMID:24625181

Johnson, James F; Bagdasarov, Zhanna; MacDougall, Alexandra E; Steele, Logan; Connelly, Shane; Devenport, Lynn D; Mumford, Michael D

2014-01-01

434

Features versus feelings: dissociable representations of the acoustic features and valence of aversive sounds.  

PubMed

This study addresses the neuronal representation of aversive sounds that are perceived as unpleasant. Functional magnetic resonance imaging in humans demonstrated responses in the amygdala and auditory cortex to aversive sounds. We show that the amygdala encodes both the acoustic features of a stimulus and its valence (perceived unpleasantness). Dynamic causal modeling of this system revealed that evoked responses to sounds are relayed to the amygdala via auditory cortex. While acoustic features modulate effective connectivity from auditory cortex to the amygdala, the valence modulates the effective connectivity from amygdala to the auditory cortex. These results support a complex (recurrent) interaction between the auditory cortex and amygdala based on object-level analysis in the auditory cortex that portends the assignment of emotional valence in amygdala that in turn influences the representation of salient information in auditory cortex. PMID:23055488

Kumar, Sukhbinder; von Kriegstein, Katharina; Friston, Karl; Griffiths, Timothy D

2012-10-10

435

Different aspects of performance feedback engage different brain areas: disentangling valence and expectancy in feedback processing.  

PubMed

Evaluating the positive and negative outcomes of our behaviour is important for action selection and learning. Such reinforcement learning has been shown to engage a specific neural circuitry including the mesencephalic dopamine system and its target areas, the striatum and medial frontal cortex, especially the anterior cingulate cortex (ACC). An intensively pursued debate regards the prevailing influence of feedback expectancy and feedback valence on the engagement of these two brain regions in reinforcement learning and their respective roles are far from being understood. To this end, we used a time estimation task with three different types of feedback that allows disentangling the effect of feedback valence and expectancy using functional magnetic resonance imaging (fMRI). Our results show greater ACC activation after unexpected positive and unexpected negative feedback than after expected feedback and by this sensitivity to unexpected events in general irrespective of their valence. PMID:25100234

Ferdinand, Nicola K; Opitz, Bertram

2014-01-01

436

Transfer of newly acquired stimulus valence between identities in dissociative identity disorder (DID).  

PubMed

Patients with Dissociative Identity Disorder (DID) frequently report episodes of interidentity amnesia, that is amnesia for events experienced by other identities. The goal of the present experiment was to test the implicit transfer of trauma-related information between identities in DID. We hypothesized that whereas declarative information may transfer from one identity to another, the emotional connotation of the memory may be dissociated, especially in the case of negative, trauma-related emotional valence. An evaluative conditioning procedure was combined with an affective priming procedure, both performed by different identities. In the evaluative conditioning procedure, previously neutral stimuli come to refer to a negative or positive connotation. The affective priming procedure was used to test the transfer of this acquired valence to an identity reporting interidentity amnesia. Results indicated activation of stimulus valence in the affective priming task, that is transfer of emotional material between identities. PMID:15629753

Huntjens, Rafaële J C; Peters, Madelon L; Postma, Albert; Woertman, Liesbeth; Effting, Marieke; van der Hart, Onno

2005-02-01

437

Physical properties and valence state of cerium in the filled skutterudite CePt?Ge??.  

PubMed

Electronic, magnetic, and transport properties of the filled platinum-germanium skutterudite CePt?Ge?? are investigated. High resolution x-ray absorption spectroscopy measurements at the cerium L(III) edge demonstrate that CePt?Ge?? in this compound has a temperature-independent valence close to three. However, magnetic susceptibility, thermopower, Hall effect, and electronic specific heat reveal a broad maximum at Tmax D 65-80 K, suggesting the presence of valence fluctuations. The Sommerfeld coefficient ? = 105 mJ mol?¹ K?², deduced from specific heat, indicates moderately enhanced band masses for CePt?Ge??. We discuss these findings and conclude that CePt?Ge?? represents a system at the border between intermediate valence (IV) and Kondo lattice behavior. In addition, the lattice specific heat and the thermal conductivity are discussed with respect to the vibrational dynamics of Ce in the [Pt?Ge??] framework. PMID:22056917

Gumeniuk, R; Kvashnina, K O; Schnelle, W; Nicklas, M; Borrmann, H; Rosner, H; Skourski, Y; Tsirlin, A A; Leithe-Jasper, A; Grin, Yu

2011-11-23

438

Angular anisotropy in valence photoionization of Na clusters: theoretical investigation using jellium model  

NASA Astrophysics Data System (ADS)

Calculation of the behaviour of photoelectron angular anisotropy in valence ionization of initially neutral NaX (X = 34-58) clusters is provided. The calculations are carried out for 1p, 1d and 1g jellium orbitals as a function of photon energy. The adapted theoretical framework is spherical jellium model using Woods-Saxon potential, which is modified to account for the long-range Coulomb tail in the final state. We discuss on the observed dramatic variations of the angular anisotropy parameter ? as a function incident photon energy. It is shown that the behaviour is connected to the oscillation of the valence photoionization cross sections, that is a specific interference property of such metallic clusters whose valence structure can be described using the jellium model. ISSPIC 16 - 16th International Symposium on Small Particles and Inorganic Clusters, edited by Kristiaan Temst, Margriet J. Van Bael, Ewald Janssens, H.-G. Boyen and Françoise Remacle.

Jänkälä, Kari

2013-03-01

439

The Electronic Properties of Nanomaterials Elucidated by Synchrotron Radiation Based Spectroscopy  

Microsoft Academic Search

The use of synchrotron radiation–based spectroscopy to investigate electronic and bonding structures of nanostructured materials is reviewed with focuses on the X-ray absorption spectroscopy (XAS), valence-band photoemission spectroscopy (VB-PES), and scanning photoelectron microscopy (SPEM) measurements. This review addresses the current status of synchrotron radiation–based nanoscale characterization of carbon-based and ZnO nanomaterials. Current research works that are relevant to this rapidly

S. C. Ray; J. W. Chiou; W. F. Pong; M.-H. Tsai

2006-01-01

440

Differential activation of amygdala Arc expression by positive and negatively valenced emotional learning conditions  

PubMed Central

Norepinephrine is released in the amygdala following negatively arousing learning conditions. This event initiates a cascade of changes including the transcription of activity-regulated cytoskeleton-associated protein (Arc) expression, an early-immediate gene associated with memory encoding. Recent evidence suggests that the valence of emotionally laden encounters may generate lateralized, as opposed to symmetric release of this transmitter in the right or left amygdala. It is currently not clear if valence-induced patterns of selective norepinephrine output across hemispheres are also reproduced in downstream pathways of cellular signaling necessary for memory formation. This question was addressed by determining if Arc expression is differentially distributed across the right and left amygdala following exposure to positively or negatively valenced learning conditions respectively. Male Sprague Dawley rats were randomly assigned to groups exposed to the Homecage only, five auditory tones only, or five auditory tones paired with footshock (0.35 mA) during Pavlovian fear conditioning. Western blot analysis revealed that Arc expression in the right amygdala was elevated significantly above that observed in the left amygdala 60 and 90 min following fear conditioning. Similarly, subjects exposed to a negatively valenced outcome consisting of an unexpected reduction in food rewards showed a greater level of Arc expression in only the right, but not left basolateral amygdala. Presenting a positively valenced event involving an unexpected increase in food reward magnitude following bar pressing, resulted in significantly greater Arc expression in the left, but not right basolateral amygdala (p < 0.01). These findings indicate that the valence of emotionally arousing learning conditions is reflected at later stages of synaptic plasticity involving the transcription of immediate early genes such as Arc. PMID:24367308

Young, Erica J.; Williams, Cedric L.

2013-01-01

441

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

Code of Federal Regulations, 2012 CFR

...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580...section 13, if, with respect to bonding coverage required under section...

2012-07-01

442

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

Code of Federal Regulations, 2014 CFR

...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580...section 13, if, with respect to bonding coverage required under section...

2014-07-01

443

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

Code of Federal Regulations, 2010 CFR

...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules § 2580...section 13, if, with respect to bonding coverage required under section...

2010-07-01

444

27 CFR 19.152 - Types of bonds.  

Code of Federal Regulations, 2011 CFR

...DEPARTMENT OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Bonds and Consents of Surety Bonding Requirements for A Dsp § 19.152 Types of bonds. (a) Basic Bonds. There are two basic types of bonds: the operations bond, and the...

2011-04-01

445

Cortical functional connectivity is associated with the valence of affective states.  

PubMed

The study investigates the relationships between the valence of affective states and the cortical patterns of functional connectivity. The information flow rate and direction were estimated by means of Directed Transfer Function (DTF), a multivariate method based on Granger causality. It was calculated on EEG activity recorded during mental imagery tasks. As a result, three regions were revealed as main network hubs, where the information outflow changed specifically with valence: the anterior orbitofrontal cortex, and the right posterior and right temporal area. The role of these structures in synchronizing the cortical affective network as well as in mediating different aspects of emotional state is discussed. PMID:25014411

Wyczesany, Miroslaw; Ferdek, Magdalena A; Grzybowski, Szczepan J

2014-10-01

446

Valence state dependent room-temperature ferromagnetism in Fe-doped ceria nanocrystals  

NASA Astrophysics Data System (ADS)

Room-temperature ferromagnetism was observed in undoped and Fe2+(3+)-doped CeO2 nanocrystals. In Fe-doped samples the enhancement of ferromagnetic ordering occurs by changing the valence state of Fe ions, whereas Raman spectra demonstrated strong electron-molecular vibrational coupling and increase in oxygen vacancy concentration. Air annealing showed degradation of ferromagnetic ordering and appearance of hematite phase in Fe3+-doped sample. The observed ferromagnetic coupling in Fe-doped samples, associated with the presence of magnetic ions mediated by single charged O2- vacancies, demonstrated that valence state of dopant has a strong influence on magnetic properties of CeO2 nanoparticles.

Doh?evi?-Mitrovi?, Z. D.; Paunovi?, N.; Radovi?, M.; Popovi?, Z. V.; Matovi?, B.; Ceki?, B.; Ivanovski, V.

2010-05-01

447

Soft-gluon resummation and the valence parton distribution function of the pion.  

PubMed

We determine the valence parton distribution function of the pion by performing a new analysis of data for the Drell-Yan process ?- N ? ?+ ?- X. Compared to previous analyses, we include next-to-leading-logarithmic threshold resummation effects in the calculation of the Drell-Yan cross section. As a result of these, we find a considerably softer valence distribution at high momentum fractions x than obtained in previous next-to-leading-order analyses, in line with expectations based on perturbative-QCD counting rules or Dyson-Schwinger equations. PMID:21231578

Aicher, Matthias; Schäfer, Andreas; Vogelsang, Werner

2010-12-17

448

Electron momentum spectroscopy study of thiophene: Binding energy spectrum and valence orbital electron density distributions  

NASA Astrophysics Data System (ADS)

Electron momentum spectroscopy has been used to measure the binding energy spectrum and momentum distributions of the valence orbitals of thiophene, which are compared with Hartree-Fock and density functional theory calculations using different-sized basis sets. Impact energy of 1200 eV plus binding energy and symmetric non-coplanar kinematics are employed. The measured binding energy spectra are compared and consistent with PES data available in the literature and also with the predictions of Green's function methods. The agreement between theory and experiment for the shape of the orbital electron momentum distributions is generally good. The satellite structure of the innermost valence orbital 6a 1 is reported.

Zhang, S. F.; Ren, X. G.; Su, G. L.; Ning, C. G.; Zhou, H.; Li, B.; Li, G. Q.; Deng, J. K.

2006-09-01

449

Smart interfacial bonding alloys  

SciTech Connect

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

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

1999-04-01

450

Method of bonding  

DOEpatents

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

Saller, deceased, Henry A. (late of Columbus, OH); Hodge, Edwin S. (Columbus, OH); Paprocki, Stanley J. (Columbus, OH); Dayton, Russell W. (Columbus, OH)

1987-12-01

451

Coordination-resolved local bond contraction and electron binding-energy entrapment of Si atomic clusters and solid skins  

SciTech Connect

Consistency between x-ray photoelectron spectroscopy measurements and density-function theory calculations confirms our bond order-length-strength notation-incorporated tight-binding theory predictions on the quantum entrapment of Si solid skin and atomic clusters. It has been revealed that bond-order deficiency shortens and strengthens the Si-Si bond, which results in the local densification and quantum entrapment of the core and valence electrons. Unifying Si clusters and Si(001) and (111) skins, this mechanism has led to quantification of the 2p binding energy of 96.089?eV for an isolated Si atom, and their bulk shifts of 2.461?eV. Findings evidence the significance of atomic undercoordination that is of great importance to device performance.

Bo, Maolin; Huang, Yongli; Zhang, Ting [Key Laboratory of Low-Dimensional Materials and Application Technologies, Xiangtan University, Hunan 411105 (China); Wang, Yan, E-mail: ywang8@hnust.edu.cn, E-mail: ecqsun@ntu.edu.sg [Key Laboratory of Low-Dimensional Materials and Application Technologies, Xiangtan University, Hunan 411105 (China); School of Information and Electronic Engineering, Hunan University of Science and Technology, Hunan 411201 (China); Zhang, Xi [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Li, Can [Center for Coordination Bond Engineering, School of Materials Science and Engineering, China Jiliang University, Hangzhou 330018 (China); Sun, Chang Q., E-mail: ywang8@hnust.edu.cn, E-mail: ecqsun@ntu.edu.sg [Key Laboratory of Low-Dimensional Materials and Application Technologies, Xiangtan University, Hunan 411105 (China); School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Center for Coordination Bond Engineering, School of Materials Science and Engineering, China Jiliang University, Hangzhou 330018 (China)

2014-04-14

452

Method for vacuum fusion bonding  

DOEpatents

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

Ackler, Harold D. (Sunnyvale, CA); Swierkowski, Stefan P. (Livermore, CA); Tarte, Lisa A. (Livermore, CA); Hicks, Randall K. (Stockton, CA)

2001-01-01

453

Fusion bonding and alignment fixture  

DOEpatents

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

Ackler, Harold D. (Sunnyvale, CA); Swierkowski, Stefan P. (Livermore, CA); Tarte, Lisa A. (Livermore, CA); Hicks, Randall K. (Stockton, CA)

2000-01-01

454

43 CFR 3904.10 - Bonding requirements.  

Code of Federal Regulations, 2011 CFR

...Interior 2 2011-10-01 2011-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds § 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2011-10-01

455

43 CFR 3904.10 - Bonding requirements.  

Code of Federal Regulations, 2012 CFR

...Interior 2 2012-10-01 2012-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds § 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2012-10-01

456

43 CFR 3904.10 - Bonding requirements.  

Code of Federal Regulations, 2014 CFR

...Interior 2 2014-10-01 2014-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds § 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2014-10-01

457

43 CFR 3904.10 - Bonding requirements.  

Code of Federal Regulations, 2013 CFR

...Interior 2 2013-10-01 2013-10-01 false Bonding requirements. 3904.10 Section 3904.10 Public Lands...MANAGEMENT-GENERAL Bonds and Trust Funds § 3904.10 Bonding requirements. (a) Prior to issuing a lease...

2013-10-01

458

Influence of 5f electrons on structure and bonding in the actinide-hydrogen intermetallics  

NASA Astrophysics Data System (ADS)

The physicochemical properties of the early actinide (through Pu) hydrides present a fascinating electronic picture that is unique in the periodic table. Complex phases form for the Th + H and U + H systems that are found with no other metals. In the Pa + H system, simple body-centered cubic, C15 Laves and A15 phases can form, dependent on temperature and composition. The phase transformations appear to be magnetically-driven, as a result of the decoupling of the metallic 5f electron bonding that occurs during hydriding; the C15 phases contain two kinds of Pa atoms - the one sublattice being still fully f-bonded and the other magnetic. This is a unique situation in solid state physics which defies a valence description. A similar situation obtains for A15 ?-UH 3 structure. It can be shown that the parent metals themselves exhibit electronegativities not unlike those of the mid-3d transition metals (e.g., Fe) because the valence electrons are tied up in metallic bonding. However, under the driving force for hydriding, the lattices can open up, decoupling the f-bonding and inducing magnetism. The systems then aggressively form very stable hydrides typical of highly-electro-positive metals. Beyond uranium the trivalent metallic state is favored and rare-earth-like hydrides are found for Np + H and Pu + H. Nevertheless, the solid-state and transport properties are markedly different than for the rare-earth hydrides, showing that the latent influence of the 5f electrons is still strong.

Ward, John W.

1985-05-01

459

Enamel-dentin crown fractures bonded with various bonding agents.  

PubMed

A method is described, by which the fracture strength of bonded, previously fractured incisors can be measured. The study employed incisors from sheep, which could be obtained in suitable numbers and with limited variation in size. The incisors were fractured parallel to the incisal edge. The mean fracture area +/- SD of central incisors was 8.45 +/- 0.89 mm2 and of lateral incisors 6.50 +/- 0.64 mm2. The enamel area constituted about 30% of the total fracture area. Acid etching of the enamel and bonding of the fractures with an unfilled resin yielded a fracture strength, which was approximately 38% of the fracture strength of fractured teeth restored with acid etching of enamel, Gluma treatment of dentin and bonding with the unfilled resin. Teeth restored in this way, but using the dentin bonding agent Tenure or Scotchbond2 instead of Gluma, exhibited mean fracture strengths which were not significantly different from that obtained when Gluma was employed as the bonding agent. The mean fracture strength by using one of the three bonding agents in combination with acid etching of enamel was about 8 MPa, which is approximately 50% of the fracture strength of intact teeth. PMID:1782898

Munksgaard, E C; Højtved, L; Jørgensen, E H; Andreasen, J O; Andreasen, F M

1991-04-01

460

Method to improve commercial bonded SOI material  

DOEpatents

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

Maris, Humphrey John (Barrington, RI); Sadana, Devendra Kumar (Pleasantville, NY)

2000-07-11

461

Ionic Bonding (www.ia.usu.edu.)  

NSDL National Science Digital Library

Atoms can join together to form compounds. There are various ways atoms can bond which are determined by the types of elements that are involved in bonding. You are going to investigate why atoms bond and one of the ways they can bond together. Please take out your periodic tables. Bonding is not haphazard. There are definite reasons and ways that atoms can bond. Click on the bold question \\"Why Bond?\\" to find the reason why atoms join other atoms to form a compound. Why Bond? According to your periodic table, what type of elements are Na and Mg? According to ...

Camp, Mrs

2007-11-28

462

Double Wells and Covalent Bonds  

NSDL National Science Digital Library

Explore tunneling splitting in double well potentials. This classic problem describes many physical systems, including covalent bonds, Josephson junctions, and two-state systems such as spin 1/2 particles and ammonia molecules.

Simulations, Phet I.; Malley, Chris; Mckagan, Sam; Perkins, Kathy; Wieman, Carl

2006-07-01

463

Are Government Bonds Net Wealth?  

Microsoft Academic Search

The assumption that government bonds are perceived as net wealth by the private sector is crucial in demonstrating real effects of shifts in the stock of public debt. In particular, the standard effects of \\

Robert J. Barro

1974-01-01

464

Bond Illiquidity and Excess Volatility  

E-print Network

We find that the empirical volatilities of corporate bond and CDS returns are higher than implied by equity return volatilities and the Merton model. This excess volatility may arise because structural models inadequately ...

Bao, Jack

465

From ligand fields to molecular orbitals: probing the local valence electronic structure of Ni(2+) in aqueous solution with resonant inelastic X-ray scattering.  

PubMed

Bonding of the Ni(2+)(aq) complex is investigated with an unprecedented combination of resonant inelastic X-ray scattering (RIXS) measurements and ab initio calculations at the Ni L absorption edge. The spectra directly reflect the relative energies of the ligand-field and charge-transfer valence-excited states. They give element-specific access with atomic resolution to the ground-state electronic structure of the complex and allow quantification of ligand-field strength and 3d-3d electron correlation interactions in the Ni(2+)(aq) complex. The experimentally determined ligand-field strength is 10Dq = 1.1 eV. This and the Racah parameters characterizing 3d-3d Coulomb interactions B = 0.13 eV and C = 0.42 eV as readily derived from the measured energies match very well with the results from UV-vis spectroscopy. Our results demonstrate how L-edge RIXS can be used to complement existing spectroscopic tools for the investigation of bonding in 3d transition-metal coordination compounds in solution. The ab initio RASPT2 calculation is successfully used to simulate the L-edge RIXS spectra. PMID:24304205

Kunnus, Kristjan; Josefsson, Ida; Schreck, Simon; Quevedo, Wilson; Miedema, Piter S; Techert, Simone; de Groot, Frank M F; Odelius, Michael; Wernet, Philippe; Föhlisch, Alexander

2013-12-27

466

The Effects of Message Valence and Listener Arousal on Attention, Memory, and Facial Muscular Responses to Radio Advertisements  

Microsoft Academic Search

This study tested the validity of using facial electromyography (EMG) as a physiological measure of the valence of radio listeners' emotional responses to advertisements and explored the effects of message valence and listener arousal on attention and memory. A within-subjects experiment was conducted in which participants listened to ten 60-second radio advertisements that had been coded in a pretest as

PAUL D. BOLLS; ANNIE LANG; ROBERT F. POTTER

2001-01-01

467

Adhesive bonding of aluminum alloys  

SciTech Connect

The topics concerned with the European chromic acid anodize process, the sealed chromic acid anodize, the phosphoric acid anodize, surface analysis, and adhesive selection are discussed. Consideration is given to epoxy adhesives, elevated-temperature-resistant adhesives, the mechanical properties of adhesives, environmental/durability testing, and coatings. Data on the use of chemical analysis for control, the structural analysis of adhesive-bonded joints, tooling design and inspection, nondestructive inspection, and adhesive-bonded aluminum structure repair are presented.

Thrall, E.W.; Shannon, R.W.

1985-01-01

468

Surface analysis in composite bonding  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

469

Low valency in lanthanides: a theoretical study of NdF and LuF.  

PubMed

The ground and low-lying excited state potential energy curves of neodymium monofluoride were calculated using multireference (CASSCF) and single reference (EOM-CR-CCSD(T)) methods. Optimized bond lengths were obtained and accurate bond dissociation energies were computed. The EOM-CR-CCSD(T) method was used to determine the bond dissociation energy of lutetium monofluoride, and it is shown that core correlation is required to produce bond dissociation energies in agreement with experiment. PMID:24929395

Schoendorff, George; Wilson, Angela K

2014-06-14