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  • 1
    Electronic Resource
    Electronic Resource
    The effect of restorative and prosthetic materials on dental plaque (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 8 (1995), S. 0 
    Details
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0757.1995.tb00049.x
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  • 2
    Electronic Resource
    Electronic Resource
    Conversion of hexaphenylcyclotrisilazane and related materials to infusible polymers and coatings (1965)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 9 (1965), S. 2811-2817 
    Details
    ISSN: 0021-8995
    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
    Notes: When hexaphenylcyclotrisilazane was heated above 450°C. at atmospheric pressure, it formed an infusible polymer of exceptional thermal and chemical stability. The polymerization, which was accompanied by elimination of benzene, is represented approximately by the equation: \documentclass{article}\pagestyle{empty}\begin{document}$\eta [({\rm C}_6 {\rm H}_5)_2 {\rm SiNH}]_3\,\, \to \,\,({\rm C}_6 {\rm H}_5 {\rm SiN})_{3n} + 3n{\rm C}_6 {\rm H}_6$\end{document} The infusible polymer was a foamed, vitreous, pale yellow solid with a high degree of stability to heat, acids, alkali, and organic solvents. A similar reaction occured with a resein that was obtained as a by-product in the preparation of hexaphenylcyclotrisilazane and with a mixture of silylamines that was obtained from the reaction of methylphenyldichlorosilane with ammonia. Coatings on aluminum and steel prepared by heating the silylamine polymers had good thermal stability and adhesion. Inclusion of a polymeric dimethylsilyl derivative of ethylenediamine improved the flexibility of the coatings.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1965.070090815
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  • 3
    Electronic Resource
    Electronic Resource
    Tryptophan Hydroxylase: Cloning and Expression of the Rat Brain Enzyme in Mammalian Cells (1996)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 67 (1996), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A cDNA encoding full-length tryptophan hydroxylase was produced by reverse transcriptase-PCR from rat brain mRNA and expressed transiently in a human fibroblast cell line. Catalytic activity was low unless transfected cells were grown in the presence of FeSO4. Recombinant tryptophan hydroxylase was found almost exclusively within the soluble compartment of the cell and was dependent on tryptophan and tetrahydrobiopterin for activity. The catalytic activity of recombinant tryptophan hydroxylase was stimulated 〉25-fold by Fe(II) and to a somewhat lesser extent by the polyanions heparin and phosphatidylserine. The enzyme was inhibited by desferrioxamine and dopamine, both of which complex iron. When extracts from transfected cells were subjected to sucrose gradient centrifugation and analytical gel filtration, the recombinant enzyme behaved the same as the native enzyme from brain. A monoclonal antibody against phenylalanine hydroxylase that cross-reacts with brain tryptophan hydroxylase was capable of immunoprecipitating the recombinant hydroxylase from solution. These data indicate that recombinant tryptophan hydroxylase expressed in mammalian cells is assembled into tetramers of ∼220,000 daltons. Its catalytic and physical properties appear to be very similar to those of the native enzyme from brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1996.67030900.x
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  • 4
    Electronic Resource
    Electronic Resource
    Time propagation and spectral filters in quantum dynamics: A Hermite polynomial perspective (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 10794-10805 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an investigation of Hermite polynomials as a basic paradigm for quantum dynamics, and make a thorough comparison with the well-known Chebyshev method. The motivation of the present study is to develop a compact and numerically efficient formulation of the spectral filter problem. In particular, we expand the time evolution operator in a Hermite series and obtain thereby an exponentially convergent propagation scheme. The basic features of the present formulation vìs a vìs Chebyshev scheme are as follows: (i) Contrary to the Chebyshev scheme Hamiltonian renormalization is not needed. However, an arbitrary time scaling may be necessary in order to avoid numerical hazards, and this time scaling also provides a leverage to accelerate the convergence of the Hermite series. We emphasize the final result is independent of the arbitrary scaling. (ii) As with the Chebyshev scheme the method is of high accuracy but not unitary by definition, and thus any deviation from unitarity may be used as a guideline for accuracy. The calculation of expansion coefficients in the present scheme is extremely simple. To contrast the convergence property of present method with that of the Chebyshev one for finite time propagation, we have introduced a time–energy scaling concept, and this has given rise to a unified picture of the overall convergence behavior. To test the efficacy of the present method, we have computed the transmission probability for a one-dimensional symmetric Eckart barrier, as a function of energy, and shown that the present method, by suitable time–energy scaling, can be very efficient for numerical simulation. Time–energy scaling analysis also suggests that it may be possible to achieve a faster convergence with the Hermite based method for finite time propagation, by a proper choice of scaling parameter. We have further extended the present formulation directed toward the spectral filter problem. In particular, we have utilized the Gaussian damping function for the purpose. The Hermite propagation scheme has allowed all the time integrals to be done fully analytically, a feature not completely shared by the Chebyshev based scheme. As a result, we have obtained a very compact and numerically efficient scheme for the spectral filters to compute the interior eigenspectra of a large rank eigensystem. The present formulation also allows us to obtain a closed form expression to estimate the error of the energies and spectral intensities. As a test, we have utilized the present spectral filter method to compute the highly excited vibrational states for the two-dimensional LiCN (J=0) system and compared with the exact diagonalization result. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480483
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  • 5
    Electronic Resource
    Electronic Resource
    Quantum dynamics of overtone relaxation in 30-mode benzene: A time-dependent local mode analysis for CH(ν=2) (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 3326-3334 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the results of a detailed quantum dynamical investigation of energy flow in 30-mode benzene. The CH(ν=2) overtone was examined by propagating an initial bright state in an active space of dimension N=16000 for 9.6 ps. Two sets of initial conditions were investigated: one in which the overtone energy was distributed as in one of the E1u symmetries appropriate for dipole excitation from the ground state and the other in which the overtone energy was localized in a single CH stretching motion. The rate and extent of energy flow out of the CH chromophore is dictated by the choice of initial conditions. Conclusions from the model where energy is localized in a single CH stretch indicate that the meta in-plane CH wags and para out-of-plane CH bend are the major recipients of bursts of energy for t≤300 fs; the ipso CH stretch retains only 10% of the overtone energy by 9.6 ps. For the E1u model, the initially excited CH stretches retain 30% of the overtone energy in long time; the ipso out-of-plane CH bend is activated before the ipso in-plane CH wag and with less energy, mimicing the results of previous classical investigations. For both models examined, energy is equipartitioned within the CC stretches, in-plane CH wags, and out-of-plane CH bends by 9.6 ps; the magnitude of energy taken up by the CC stretches and in-plane CH wags is the same. CCC in-plane bends and CCCC out-of-plane ring torsions are of relatively minor importance (on the time scale considered) in intramolecular vibrational energy redistribution in benzene. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478198
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum mechanical study of the CH(v=2) overtone in 30-mode benzene (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 10732-10739 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The results of large-scale quantum mechanical calculations of the CH(v=2) 1st overtone spectrum for 30-mode benzene are reported. This overtone was chosen for investigation because of its high degree of fragmentation and resulting complexity compared to spectra for the fundamental and higher overtones. These calculations use the best available ab initio force field supplemented by higher-order terms for the CH stretch–wag interaction. The dynamical calculations were conducted in large active spaces with 12 000 or 16 000 vibrational basis functions. The recursive residue generation method was used to compute residues (intensities) and eigenvalues. From these quantities, the lineshape function, survival probabilities, and vibrograms were computed. Wherever possible, these results were compared to experimental overtone spectra and to other computational results. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477772
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  • 7
    Electronic Resource
    Electronic Resource
    Helium pressure broadening of ammonia inversion transitions from 10 to 35 K (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8252-8261 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Helium pressure broadening cross sections for the (J,K)=(1,1), (2,2) and (3,3) inversion transitions of ammonia were measured at temperatures from 10 to 35 K. Measurements were taken in a quasiequilibrium cell using the collisional cooling technique. In contrast to the situation at room temperature where there is little state-to-state variation in helium pressure broadening cross sections, at low temperature the (3,3) cross sections were found to be, on average, three times larger than the (1,1) cross sections while the (2,2) cross sections were twice as large as the (1,1) values. The major factor determining the relative size of the low temperature cross sections appears to be the contribution from inelastic collisions into lower energy levels. The relative size of the cross sections thus scales with the number of rotational levels underlying a given (J,K) state. Cross sections were also calculated for comparison with the experimental data using three existing NH3–He potential surfaces. Overall, none of the three surfaces gave consistent agreement with the experimental results for all three observed transitions. The discrepancy between experiment and theory was greatest for the (3,3) data. This may be a manifestation of a previously observed tendency of NH3–He potential surfaces to underestimate the contribution from parity-conserving collisions in calculated state-to-state rates. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475308
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  • 8
    Electronic Resource
    Electronic Resource
    Computational study of many-dimensional quantum vibrational energy redistribution. II. Statistics of the spectrum with dynamical Implications (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 7047-7054 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We continue a study in which we statistically analyze the dynamics of vibrational energy flow in a model system of anharmonic oscillators which are nonlinearly coupled, with a local topology. Average spectra are obtained from individual spectra of many basis states of similar energy, for different values of the magnitude of the coupling between states. The survival probabilities of the density are then determined from the average spectra. When the average fluctuation in spectral intensities is small then the density survival probability closely follows the average survival probability presented in our earlier paper for short times. For longer times, when the average survival probability shows a power law decay, this decay does not appear in the density survival probability. In addition, when spectral fluctuations are large, the two survival probabilities differ strongly. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473728
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  • 9
    Electronic Resource
    Electronic Resource
    AUTHORS' REPLY (1995)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 102 (1995), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1995.tb11349.x
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  • 10
    Electronic Resource
    Electronic Resource
    Expression and Deletion Mutagenesis of Tryptophan Hydroxylase Fusion Proteins: Delineation of the Enzyme Catalytic Core (1996)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 67 (1996), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: cDNAs encoding the full-length sequence for tryptophan hydroxylase, and deletion mutants consisting of the regulatory (amino acids 1–98) or catalytic (amino acids 99–444) domains of the enzyme, were cloned and expressed as glutathione S-transferase fusion proteins in E. coli. The recombinant fusion proteins could be purified to near homogeneity within minutes by affinity chromatography on glutathione-agarose. The full-length enzyme and the catalytic core expressed very high levels of tryptophan hydroxylase activity. The regulatory domain was devoid of activity. The full-length enzyme and the catalytic core, while adsorbed to glutathione-agarose beads, obeyed Michaelis-Menten kinetics, and the kinetic properties of each recombinant enzyme for cofactor and substrate compared very closely to native, brain tryptophan hydroxylase. Both active forms of the glutathione S-transferase-tryptophan hydroxylase fusion proteins had strict requirements for ferrous iron in catalysis and expressed much higher levels of activity (Vmax) than the brain enzyme. Analysis of full-length tryptophan hydroxylase and the catalytic core by molecular sieve chromatography under nondenaturing conditions revealed that each fusion protein behaved as a tetrameric species. These results indicate that a truncated tryptophan hydroxylase, consisting of amino acids 99–444 of the full-length enzyme, contains the sequence motifs needed for subunit assembly. Both wild-type tryptophan hydroxylase and the catalytic core are expressed as apoenzymes which are converted to holoenzymes by exogenous iron. The tryptophan hydroxylase catalytic core is also as active as the full-length enzyme, suggesting the possibility that the regulatory domain exerts a suppressive effect on the catalytic core of tryptophan hydroxylase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1996.67030917.x
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