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  • 1
    Electronic Resource
    Electronic Resource
    Excitation shifts of parallel conjugated polymers due to π-electron dispersion forces (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7439-7448 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular exciton methods are extended to obtain excited-state shifts of parallel conjugated strands arising from interchain Coulomb interactions. A method is developed to evaluate second-order corrections involving π-electron dispersion forces, with exact Pariser–Parr–Pople states of isolated segments as zeroth-order functions. Crystal shifts are estimated for polyacetylene (PA) at interchain separation d=3.9 A(ring); the two-photon excitation to the covalent 2 1Ag state is hardly shifted, but the one-photon excitation to 1 1Bu is red shifted by ∼0.30 eV and specific higher n 1Ag states are strongly red shifted by ∼1 eV. Their stabilization correlates with charge separation and ionicity in the excited state. Excitation shifts due to π-electron dispersion forces do not parallel changes in the static polarizability and show unusual long-range behavior of d−3 in the interchain separation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459715
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  • 2
    Electronic Resource
    Electronic Resource
    Interchain dispersion and second hyperpolarizability of conjugated polymers (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2127-2134 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: π-electron dispersion forces between parallel conjugated strands are shown to alter χ(3) coefficients, even in the limit of nonoverlapping strands, through dipole processes involving virtual excitation and deexcitation of adjacent strands. The position and relative intensity of two- and three-photon resonances in the third-harmonic-generation (THG) spectrum depend both on the strength of interchain dispersion forces and on the lattice coordination z. The admixture of even-parity states above the one-photon gap Eg with biexcitons on adjacent strands shifts the two-photon resonance to lower energy and reduces its amplitude, while the amplitude of the three-photon resonance at Eg/3 increases with z due to new biexcitonic pathways. THG spectra based on exact solutions to Pariser–Parr–Pople (PPP) models of polyenes are reproduced by a dimer model for each strand. Interchain dispersion in the lattice of dimers leads to an exciton problem whose solution explicitly gives the dependence on interchain dispersion, intrachain correlations, and lattice coordination. Interchain dispersion in polyacetylene, with z=6 neighboring strands in van der Waals contact, accounts qualitatively for its THG spectrum, while two-photon processes in conjugated polymers whose backbones are separated by bulky side groups are in accord with single-strand PPP results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461011
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  • 3
    Electronic Resource
    Electronic Resource
    Water quality during egg incubation influences yolk-sac fry sodium kinetics in Atlantic salmon, Salmo salar L.: a possible mechanism of adaptation to acid waters (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 39 (1991), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Atlantic salmon (Salmo salar L.) fry hatched from eggs transferred from high-Na to low-Na water during the eyed stage of development had a significantly higher Vmax and lower Km (P 〈0.01) of the sodium uptake mechanism than fry hatched from eggs incubated entirely in low-Na or high-Na water.Fry hatched from eggs transferred to acid, high aluminium water during the eyed stage of development had a similar Vmax and Km to fry hatched from eggs incubated entirely in high- or low-Na water. Eggs incubated continuously in acid, high aluminium (low-Na) water produced fry with significantly lower Km and Vmax values than fry hatched from eggs incubated continuously in low-Na water. Eggs and fry in acid, high aluminium water continually lost sodium and mortality was 100% at 5 5 M O degree-days (2–3 weeks after hatching).The results are discussed with respect to the influence of perivitelline fluid ion activities in eggs in acid, high aluminium water on the kinetic characteristics of sodium uptake in yolk-sac fry. A possible mechanism for the long-term adaptation of teleosts in acidified natural waters is also proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1991.tb04379.x
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  • 4
    Electronic Resource
    Electronic Resource
    Reply to the Comment on: Interchain dispersion and second hyperpolarizability of conjugated polymers (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 2172-2173 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463109
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  • 5
    Electronic Resource
    Electronic Resource
    Environmental induction of Na+ transporter affinity in Atlantic salmon embryos (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 42 (1993), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Atlantic salmon (Salmo salar L.) alevins hatched from eggs transferred from high- to low-Na water at 250° days, before the onset of the phase of increasing whole egg sodium content (at ∼380°days), showed a significantly reduced Km for Na+ transport, whereas transfer at 400° days did not produce any change in Km. Alevins hatched from eggs given acid shocks of 1, 3, 7 or 14 days duration initiated at 250 or 400° days showed no significant changes in Na+ transporter Km. Extended acid exposure (38 days) from 250°days to hatching resulted in a slight lowering of Km (P〈0.05). A 24-day acid exposure from 400°days to hatching had no effect on Na+ transporter Km. Alevins hatched from eggs incubated throughout in acidified water had a significantly reduced Km compared to controls (P〈0.01).The timing and duration of periods of Na depletion of eggs is considered with respect to environmental induction of increased Na transporter affinity in teleost embryos as a mechanism of long-term physiological adaptation to the gradual acidification of natural waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1993.tb00310.x
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetic characteristics of the sodium uptake mechanism during the development of embryos and fry of Atlantic salmon, Salmo salar L., in an improved water quality (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 35 (1989), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The kinetics of active sodium uptake in dechorionated embryos, yolk-sac fry and start-feed fry of Atlantic salmon were compared in two groups reared either in low conductivity, untreated, river water (conductivity ∼ 46 μS cm−1, pH 5.75), or in ‘improved’ river water buffered with sea water (conductivity ∼2200 μS cm 1, pH 6.56), the latter treatment often being used in commercial hatcheries to avoid problems associated with periodic acidification.Maximal transport rate (Vmax) increased during development in both groups but was always significantly higher in embryos and fry maintained in untreated river water. Values for Km were not seen to vary during development up to 12 weeks after hatching and were not significantly different between groups, or from values reported for adult Atlantic salmon in fresh water.The results are discussed with respect to the influence of Na+ concentrations in the perivitelline fluid of developing eggs and in the external medium surrounding fry on Vmax and Km. The ability of fry reared entirely in buffered river water to maintain sodium balance following transfer to untreated river water is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1989.tb03037.x
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  • 7
    Electronic Resource
    Electronic Resource
    Ionic regulation by the eggs of salmon (1989)
    Springer
    Journal of comparative physiology 159 (1989), S. 249-254 
    Details
    ISSN: 1432-136X
    Keywords: Salmon eggs ; Ionic regulation ; Perivitelline fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. In both river water (RW) and in river water neutralised with seawater (RSW) an electrochemical gradient of K+ and Na+ exists, between perivitelline fluid and external water, which tends to drive these ions out of the egg. A similar gradient of Ca2+ and Cl− exists in RW eggs. 2. The results point to an effective external permeability barrier to electrolytes which may be the chorion or a combination of chorion and perivitelline fluid. 3. Eggs incubated in both RW and RSW maintained their ion contents. Na+ may accumulate in eggs in later stages of development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00691501
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of pH and calcium concentrations on gill potentials in the Brown Trout,Salmo trutta (1978)
    Springer
    Journal of comparative physiology 126 (1978), S. 277-286 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Measurements of the transepithelial potential (Vint-Vext) across the gills of Brown Trout,Salmo trutta, were made in solutions of a range of pH and calcium concentrations. The potential was strongly dependent on external pH, being negative in neutral solutions but positive in acid solutions. The addition of calcium to the external medium produced a positive shift in potential in all but very acid media (pH 4.0–3.5), where very little change was seen. The gill membrane appears to act as a hydrogen electrode having a very high permeability to H+ ions, and the potential behaves as a diffusion potential. The presence of calcium reduced the permeability to both H+ and Na+ ions but even at a calcium concentration of 8.0 mM/l the permeability ratio ΦH+/ΦNa+ was still more than 900. The transepithelial potential is shown to be diffusional in origin and is discussed in terms of the relative permeability of the gill to H+, Na+ and Cl− ions. Sodium fluxes across the gills were measured and provide the basis for a theoretical consideration of Na+, Cl− and H+ fluxes across the gills in neutral and acid solutions. The positive potential at low pH largely accounts for the increased loss of sodium from fish in these conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688938
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  • 9
    Electronic Resource
    Electronic Resource
    Exact nonlinear optical coefficients of quantum cell models with interacting electrons (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 37-60 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diagrammatic valence-bond (DVB) methods yield exact dynamic nonlinear optical (NLO) coefficients for π-electron models of conjugated molecules and polymers. We contrast exact coefficients with mean-field or Hückel results and discuss several qualitative differences. The length and alternation dependencies of NLO spectra for Pariser-Parr-Pople (PPP) models provide a unified treatment of even-parity states and two-photon processes in polyenes, polydiacetylenes, and polysilanes. We emphasize relationships between one- and two-photon spectra, correlation effects involving both parallel and transverse NLO coefficients, and the nature of correlated states in polar conjugated molecules and in polymers with centrosymmetric backbones.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560430107
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  • 10
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    M3-muscarinic receptor promotes insulin release via receptor phosphorylation/arrestin-dependent activation of protein kinase D1 (2010)
    National Academy of Sciences
    Details
    Publication Date: 2010-11-15
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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