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  • 1
    Electronic Resource
    Electronic Resource
    The multiphoton dissociation of acetylene. I. Long-lived intermediates, sequential and concerted processes of dissociation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7832-7841 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multiphoton dissociation processes of acetylene via a two-photon resonant predissociative state, v=0 of 1Σ+g, have been studied by three techniques: time-resolved photofragment excitation spectroscopy (TRPFES), laser-induced fluorescence (LIF) of the C2 fragments, and dispersed emission. We found that the major dissociation products are H atoms, H2 molecules, and C2 molecules in the X 1Σ+g, a 3Πu and A 1Πu states; among the latter, C2 X 1Σ+g molecules are formed by a sequential bond–rupture mechanism whereas some C2 in a 3Πu is formed by a concerted two-bond fission process. Other, minor dissociation channels due to three-photon processes, such as C2(d 3Πg)+2H(2S(1)/(2)), C2(d 3Πg)+H2(X 1Σ+g), C2(C 1Πg)+H2(X), C2(e 3Πg)+H2(X), and C2(D 1Σ+u)+H2(X), were also detected. In the 2+1 concerted dissociation yielding C2(C 1Πg)+H2(X), a long-lived intermediate C2H2, likely a cis isomer or other conformer in which the hydrogen atoms are relatively close to each other, was revealed by TRPFES; its zero-pressure lifetime was estimated to be (8±1) μs. A long-lived intermediate C2H was also found in the 2+1 sequential dissociation by TRPFES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460118
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular basis for the antisickling activity of aromatic amino acids and related compounds: a proton nuclear magnetic resonance investigation (1986)
    s.l. : American Chemical Society
    Biochemistry 25 (1986), S. 808-815 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00352a012
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of nonadiabatic electron transfer at electrode/liquid interfaces: Role of quantum effects (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 11117-11137 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electron transfer rate constant at electrode/liquid interfaces is theoretically described on the basis of the Anderson–Newns–Schmickler model. A compact formula for the rate constant is derived in the nonadiabatic limit, which is expressed in terms of the spectral density of surrounding media, the density of states of electrons in the electrode, and the weighted electronic coupling constant between the electrode and the redox couple in the liquid. The outer-sphere spectral density is then related to the experimentally accessible data on the frequency-dependent dielectric response functions of the solvent and the electrode with the aid of the dielectric continuum approximation. The derived formula provides a quantum-mechanical extension of the conventional nonadiabatic expression for the heterogeneous electron transfer reactions at electrode/liquid interfaces, taking into account the quantum effects associated with the high-frequency modes of both outer and inner spheres. On this basis, the quantum correction for the electron-transfer rate constant is numerically analyzed for some metal or semiconductor electrodes in contact with the Fe2+/3+ redox couple dissolved in water solvent at room temperature. In the case of zero energy gap, the quantum correction is found to be a factor of 4–5 for a typical configuration of the redox couple regardless of the species of electrode, while the rate constant itself is significantly affected by the dielectric property of the electrode. The energy gap dependence of the quantum correction is also discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480471
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  • 4
    Electronic Resource
    Electronic Resource
    Reaction field cavity optimization: A born-again Born model for ionic hydration (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 9700-9704 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a new quantum reaction field model, the electronic reaction field (ERF), which does not require the empirical specification of cavity shape and size. We demonstrate our approach on one of the simplest reaction field theories, the Born model for aqueous atomic ion solvation. The ERF model enforces complete solute–solvent separability so that the solute wave function is optimized under the boundary condition that it is fully contained within the cavity. This model imposes the exact condition necessary for treating the solute quantum mechanically and the other as a macroscopic classical dielectric, and allows the testing of the primary assumption in the dielectric continuum approximation that the molecular character of solvent is unimportant. We show that the Born theory for monovalent and divalent cations is consistent with ERF model enforcing full wave function containment, while strict solute–solvent separability gives a poor description for anions of any valency. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480303
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  • 5
    Electronic Resource
    Electronic Resource
    Linear response in theory of electron transfer reactions as an alternative to the molecular harmonic oscillator model (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5307-5317 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of solvent fluctuations on the rate of electron transfer reactions is considered using linear response theory and a second-order cumulant expansion. An expression is obtained for the rate constant in terms of the dielectric response function of the solvent. It is shown thereby that this expression, which is usually derived using a molecular harmonic oscillator ("spin-boson") model, is valid not only for approximately harmonic systems such as solids but also for strongly molecularly anharmonic systems such as polar solvents. The derivation is a relatively simple alternative to one based on quantum field theoretic techniques. The effect of system inhomogeneity due to the presence of the solute molecule is also now included. An expression is given generalizing to frequency space and quantum mechanically the analogue of an electrostatic result relating the reorganization free energy to the free energy difference of two hypothetical systems [J. Chem. Phys. 39, 1734 (1963)]. The latter expression has been useful in adapting specific electrostatic models in the literature to electron transfer problems, and the present extension can be expected to have a similar utility. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478425
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic Stokes shift in solution: Effect of finite pump pulse duration (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 7356-7366 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The time-evolution of the fluorescence spectrum of a dissolved chromophore excited by an ultrafast pump pulse is considered. The average value of the energy difference of the solute in its excited and ground states is used to describe the relaxation of the maximum of the transient fluorescence spectrum to its equilibrium value (dynamic Stokes shift, DSS). A simple formula for the normalized DSS is obtained which generalizes an earlier standard classical expression and includes the effect of a pump pulse of finite duration. As an example, dielectric dispersion data are used for a dipolar solute in water to estimate the quantum correction to the standard DSS expression. The correction is negligible when the frequency of the pump pulse is close to the maximum in the absorption spectrum, but a deviation from the standard formula can be expected for the pump pulse tuned to a far wing of the absorption band of the chromophore. An expression is given for this deviation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476155
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  • 7
    Electronic Resource
    Electronic Resource
    A sequential formula for electronic coupling in long range bridge-assisted electron transfer: Formulation of theory and application to alkanethiol monolayers (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 584-598 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A recursion relation is formulated for the Green's function for calculating the effective electron coupling in bridge-assisted electronic transfer systems, within the framework of the tight-binding Hamiltonian. The recursion expression relates the Green's function of a chain bridge to that of the bridge that is one unit less. It is applicable regardless of the number of orbitals per unit. This method is applied to the system of a ferrocenylcarboxy-terminated alkanethiol on the Au(111) surface. At larger numbers of bridge units, the effective coupling strength shows an exponential decay as the number of methylene(–CH2–) units increases. This sequential formalism shows numerical stability even for a very long chain bridge and, since it uses only small matrices, requires much less computer time for the calculation. Identical bridge units are not a requirement, and so the method can be applied to more complicated systems.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473398
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  • 8
    Electronic Resource
    Electronic Resource
    Excitation energy transfer in condensed media (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3065-3072 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We derive an expression for resonance energy transfer between a pair of chromophores embedded in a condensed medium by considering the energy splitting of the chromophores from their resonant excited states. We employ time-dependent density functional response theory in our derivation. The linear response theory treatment is rigorous within the framework of time-dependent density functional theory, while in obtaining the energy transfer coupling, the standard first-order approximation is used. The density response function for the medium, which can be replaced by the macroscopic dielectric susceptibility, enables the inclusion of the medium influence on the energy transfer coupling between the donor and acceptor. We consider the Coulomb coupling, and determine that our result is isomorphic to the Coulomb interaction between two charge densities inside a dielectric medium. The isomorphism we found not only provides a general and useful expression for applications, but additionally offers a basis for the extension of the dielectric response model to energy transfer coupling, which has been implicitly used earlier. An illustrative model shows that for two separated molecules, the medium adds a dielectric screening effect to the Coulomb coupling of their transitions. However, if the two molecules are so closely spaced that they effectively reside in a single cavity, the medium can enhance or reduce the strength of the coupling depending on the orientation and the alignment of the two chromophores. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1338531
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  • 9
    Electronic Resource
    Electronic Resource
    An improved neural network model for the prediction of cutting tool life (1997)
    Springer
    Journal of intelligent manufacturing 8 (1997), S. 107-115 
    Details
    ISSN: 1572-8145
    Keywords: Backpropagation neural network ; self-adjusting ability ; screening variables ; test for normality ; cutting experiments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In recent years, the backpropagation neural network has been shown to be a good modelling method for complex problems because of its self-adjusting ability, and the fact that it can be used with small amounts of data. However, some factors in the data may be insignificant and correlated, or there may be some noise present. These phenomena will cause the model to predict inaccurately. In this research, we propose a statistical method to avoid such situations, by screening variables and testing for normality. The model built by using screened variables shows a better fit and yields accurate predictions. To demonstrate the proposed method, we conduct cutting experiments and build cutting tool life models as an example. Then we compare the results of the constructed models among the backward stepwise regression, the neural network and the proposed neural network methods. The proposed neural network method shows the most accurate prediction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018552620196
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  • 10
    Electronic Resource
    Electronic Resource
    On Subfields of the Hermitian Function Field (2000)
    Springer
    Compositio mathematica 120 (2000), S. 137-170 
    Details
    ISSN: 1570-5846
    Keywords: function fields ; rational places ; finite fields.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The Hermitian function field H= K(x,y) is defined by the equationy q+ y=x q+1(q being a powerof the characteristic of K). OverK= $${\mathbb{F}}$$ q 2 it is a maximalfunction field; i.e. the numberN(H)of $${\mathbb{F}}$$ q2-rationalplaces attains the Hasse--Weil upper boundN(H)=q 2+1+2g(H)·q.All subfields K ⊂ ≠ E⊂Hare also maximal.In this paper we construct a large number of nonrational subfields E⊂H, by considering the fixed fieldsH $$G$$ under certaingroups $$G$$ type="Italic"〉g≥0 that occur as the genus of some maximal function field over $${\mathbb{F}}$$ q 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001736016924
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