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  • Electronic Resource  (8)
  • 1995-1999  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Morphine Tolerance and Physical Dependence: Reversal of Opioid Inhibition to Enhancement of Cyclic AMP Formation (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: This laboratory has previously demonstrated that the μ-selective opiate receptor agonist sufentanil can produce a naloxone-reversible increase or decrease in the stimulated formation of cyclic AMP (cAMP) in the myenteric plexus, depending on the concentration of opioid used. On the basis of these results, it was suggested that μ-opiate receptors are positively as well as negatively coupled to adenylyl cyclase. In the present study, the effect of chronic morphine exposure, in vivo, on the magnitude of electrically stimulated formation of cAMP and its modulation by sufentanil was investigated. In chronic morphine-treated preparations, the magnitude of electrically stimulated cAMP formation, while in the presence of an inhibitory (10−6M) concentration of sufentanil, is indistinguishable from the formation that occurs in opiate-naive preparations (in the absence of exogenous opioid). This indicates that the negative modulation of stimulated enteric cAMP formation by sufentanil manifests tolerance. Paradoxically, however, in “addicted tissue” the magnitude of the increase in cAMP formation produced by electrical stimulation in the presence of a previously inhibitory concentration of sufentanil is significantly larger than in its absence. Thus, the equivalence between the magnitude of stimulation-induced increase in cAMP formation observed in naive versus tolerant/dependent tissue, while in the presence of sufentanil, is due to the ability of an originally inhibitory concentration of opioid to enhance or facilitate stimulated formation of cAMP. It is suggested that tolerance/dependence to the opioid inhibition of stimulated cAMP formation results not only from the loss of inhibitory potency but also from its reversal to enhancement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.64031102.x
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  • 2
    Electronic Resource
    Electronic Resource
    Altered μ-Opiate Receptor-G Protein Signal Transduction Following Chronic Morphine Exposure (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 68 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: This laboratory has demonstrated that the longitudinal muscle/myenteric plexus (LMMP) preparation manifests pleiotropic responses to opioid agonists. For example, the μ-selective opiate receptor agonist sufentanil can produce a naloxone-reversible increase or decrease in the electrically stimulated formation of cyclic AMP, depending on its concentration. The present study demonstrates that the sufentanil facilitation and inhibition of stimulated cyclic AMP formation are mediated via Gs- and Gi-like G proteins, respectively. Inactivation of Gi (via pertussis toxin) not only abolishes sufentanil inhibition of cyclic AMP formation but also unmasks a facilitory effect. The latter response is eliminated following treatment with cholera toxin. In tolerant/dependent LMMP tissue, previously inhibitory concentrations of sufentanil produce a facilitation of cyclic AMP formation. However, this unmasked facilitory effect is resistant to cholera toxin. Thus, although inactivation of the inhibitory signal transduction pathway (via pertussis toxin) is sufficient to unmask excitatory sufentanil effects in opiate naive preparations, this mechanism cannot explain the reversal of sufentanil inhibition to facilitation that is observed in tolerant/dependent tissue. Instead, the chronic morphine-induced emergence of a μ-opiate receptor-coupled facilitory pathway that is either not expressed or not fully manifest in opiate naive LMMP tissue is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.68010248.x
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  • 3
    Electronic Resource
    Electronic Resource
    Electronic consequences of random layer-thickness fluctuations in AlAs/GaAs superlattices (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6639-6657 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the effects of a few types of atomic disorder on the electronic and optical properties of AlAs/GaAs (001) and (111) superlattices: (i) atomic intermixing across the interfaces; (ii) replacing a single monolayer in a superlattice by one containing the opposite atomic type (isoelectronic δ doping); and (iii) random layer-thickness fluctuations in superlattices (SL). Type (i) is an example of lateral disorder, while types (ii) and (iii) are examples of vertical disorder. Using three-dimensional empirical pseudopotential theory and a plane-wave basis, we calculate the band gaps, electronic wave functions, and optical matrix elements for systems containing up to 2000 atoms in the computational unit cell. Spin-orbit interactions are omitted. Computationally much less costly effective-mass calculations are used to evaluate the density of states and eigenstates away from the band edges in vertically disordered SLs. Our main findings are: (i) Chemical intermixing across the interface can significantly shift the SL energy levels and even change the identity (e.g., symmetry) of the conduction-band minimum in AlAs/GaAs SLs; (ii) any amount of thickness fluctuations in SLs leads to band-edge wave-function localization; (iii) these fluctuation-induced bound states will emit photons at energies below the "intrinsic'' absorption edge (red shift of photoluminescence); (iv) monolayer fluctuations in thick superlattices create a gap level whose energy is pinned at the value produced by a single δ layer with "wrong'' thickness; (v) (001) AlAs/GaAs SLs with monolayer thickness fluctuations have a direct band gap, while the ideal (001) superlattices are indirect for n〈4; (vi) there is no mobility edge for vertical transport in a disordered superlattice, because all the states are localized; however, the density of states retains some of the features of the ordered-superlattice counterpart. We find quantitative agreement with experiments on intentionally disordered SLs [A. Sasaki, J. Cryst. Growth 115, 490 (1991)], explaining the strong intensity and large red shift of the photoluminescence in the latter system. We provide predictions for the case of unintentional disorder. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360728
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of the k⋅p and the direct diagonalization approaches for describing the electronic structure of quantum dots (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3433-3435 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that the standard (decoupled) 6×6 k⋅p effective-mass approach for semiconductor quantum dots overestimates significantly the hole and electron confinement energies, and, for dots made of materials with small spin-orbit coupling (e.g., phosphides, sulphides) produces a reverse order of s- and p-like valence states. By contrasting the electronic structures of dots as obtained by a direct diagonalization (multiband) pseudopotential approach and by its k⋅p approximation, we are able to trace the systematic errors of k⋅p in dots to the k⋅p errors in the underlying bulk solids. This suggests a "diagnostic tool" and a strategy for improving the k⋅p. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120421
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  • 5
    Electronic Resource
    Electronic Resource
    Response to "Comment on ‘Comparison of the k⋅p and the direct diagonalization approaches for describing the electronic structure of quantum dots' " [Appl. Phys. Lett. 73, 1155 (1998)] (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1157-1158 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122155
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  • 6
    Electronic Resource
    Electronic Resource
    Blue polymer light-emitting diodes from poly(9,9-dihexylfluorene-alt-co-2, 5-didecyloxy-para-phenylene) (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3270-3272 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep blue photoluminescence and electroluminescence are demonstrated from a soluble conjugated polymer, poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-para-phenylene). The PL quantum efficiency is approximately 40%. Cyclic voltammetry measurements indicate that the highest occupied molecular orbital and lowest unoccupied molecular orbital energies are 5.66 and 2.62 eV below vacuum, respectively. Single-layer and multilayer light-emitting diodes emit deep blue light (peak at ∼420 nm). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125321
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  • 7
    Electronic Resource
    Electronic Resource
    Vinyl monomers bearing chromophore moieties and their polymers. IV. Fluorescence and photosensitizing behavior of 8-acryloyloxyquinoline and its polymer (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1087-1093 
    Details
    ISSN: 0887-624X
    Keywords: 8-acryloyloxyquinoline ; poly(8-acryloyloxyquinoline) ; fluorescence ; polymerizable photosensitizer ; structural self-quenching effect ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acrylic monomers bearing electron-donating quinolyl moiety, i.e., 8-acryloyloxyquinoline (AQ) was prepared and polymerized. It was found that the fluorescence intensity of AQ was much lower than that of P(AQ) at the same chromophore concentration. The fluorescence of P(AQ) could be quenched by electron-deficient vinyl monomers, such as acrylonitrile (AN) and methyl methacrylate (MMA). This is another example of the “fluorescence structural self-quenching effect” termed by us previously, and demonstrates again that this phenomenon is not an accidental but a general one for acrylic monomers bearing electron-donating chromophores. The photopolymerization of acrylonitrile (AN) sensitized by AQ and P(AQ) as well as combining with carbon tetrabromide (CBr4) was studied kinetically. From the rates of the polymerization (Rp) and overall activation energies obtained for these four systems, it was found that Rp sensitized by the binary systems was much higher than by AQ or P(AQ) alone, while the molecular weights of the resulting P(AN) were lower. The fluorescent analysis of the resulting P(AN) in solution showed that the sensitizers also entered into the P(AN) chains. A mechanism of charge transfer complex (CTC) formation was tentatively suggested for the photopolymerization of AN initiated by these four systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1087-1093, 1997
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Facile approach to a chemisorbed thin film of functionalized polythiophene on a glass surface (1997)
    Weinheim : Wiley-Blackwell
    Advanced Materials 9 (1997), S. 887-891 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19970091106
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