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  • 1
    Electronic Resource
    Electronic Resource
    Porosity effects on catalytic char oxidation. Part I: A catalyst deposition model (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 957-964 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Six char samples generated from two coals were impregnated by solutions with different concentrations of Na2CO3 and /or K2CO3. The catalyst solution penetration was studied, the catalyst uptake was measured, and the effects of impregnation on the char pore structure were determined experimentally. The results indicate that the impregnated catalysts reside only on particle exteriors without significant penetration. The overall rate of reaction is therfore the combination of catalytic reaction on particle exteriors and noncatalytic reaction on the pore surfaces inside the particle. A kinetic model is presented that takes these findings into account.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310612
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Porosity effects on catalytic char oxidation. Part II: Experimental results (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 965-972 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxidation rates of Na2CO3- and K2CO3-impregnated char samples were measured in an isothermal kinetic control regime. The results were analyzed by a previously developed model to extract the intrinsic catalytic reactivities, freed from superimposed noncatalytic and structural effects. Although the overall catalyzed rates are only several times greater than their uncatalyzed counterparts, the intrinsic catalytic rates were found to be four orders of magnitude greater. The results further indicate that the function of the catalyst is to increase the number of active sites without affecting the activation energy. The overall reaction kinetics are demonstrated to contain the combined contributions of both catalytic and noncatalytic reactions, and in this context the effects of multiple catalysts as well as of the pore structure development during reaction can be understood and interpreted.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310613
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of pore structure on char oxidation kinetics (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 973-981 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Prior studies have demonstrated that char gasification rates vary with conversion, showing a maximum at an intermediate level. In this work experimentally determined char-air reaction rates and corresponding pore structures are compared to assess the applicability of a previously proposed random pore model and to extract pertinent chemical and physical parameters. Results on six different chars are presented and analyzed to obtain structure parameters, intrinsic kinetics, and activation energies. Agreement between two independent evaluations of the structure parameters demonstrates the degree of applicability of the random pore model and supports the view that rate variations with conversion are controlled by pore structural changes, even though overall rates also include contributions of intrinsic reactivity.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310614
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of chemisorbed oxygen on char reactivity (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1725-1727 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690311017
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  • 5
    Electronic Resource
    Electronic Resource
    Ferroelectric and piezoelectric properties of nylon 11/poly(vinylidene fluoride) bilaminate films (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 85-91 
    Details
    ISSN: 0887-6266
    Keywords: ferroelectricity ; piezoelectricity ; bilaminate ; nylon 11 ; PVF2 ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ferroelectric and piezoelectric properties of a new class of polymer ferroelectric and piezoelectric materials, nylon 11/polyvinylidene fluoride (PVF2) bilaminate films, prepared by a co-melt-pressing method, is presented. The bilaminate films exhibit typical ferroelectric D-E hysteresis behavior with a remanent polarization, Pr, of about 75 mC/m2, which is higher than the value of 52 mC/m2 observed for PVF2 or nylon 11 films measured under the same conditions. The coercive field, Ec, of the bilaminate films is ∼ 78 MV/m, which is higher than that of either PVF2 or nylon 11 films. Measurements of the temperature dependence of the piezoelectric strain coefficient, d31, and the piezoelectric stress coefficient, e31, were also carried out. The bilaminate films exhibit a piezoelectric strain coefficient, d31, of 41 pC/N at room temperature, which is significantly higher than the PVF2 films (25 pC/N) and the nylon 11 films (3.1 pC/N). When the temperature is increased to 110°C, d31 of the bilaminate films reaches a maximum value of 63 pC/N, more than five times that of PVF2 (11 pC/N) and more than four times that of nylon 11 (14 pC/N) at the same temperature. The piezoelectric stress coefficient, e31, of the bilaminate films shows a value of 109 mC/m2 at room temperature, almost twice that of the PVF2 films (59 mC/m2) and about 18 times that of the nylon 11 films (6.2 mC/m2). Measurement of the temperature dependence of the hydrostatic piezoelectric coefficient, dh, of the bilaminate films also shows an enhancement with respect to the individual components, PVF2 and nylon 11. ©1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330110
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  • 6
    Electronic Resource
    Electronic Resource
    The rate of methyl radical decomposition at high temperatures and pressuresDedicated to the memory of R.A. Back. (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 26 (1994), S. 159-169 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants are calculated for CH3 (+ Ar) ⇄ CH2 + H (+ Ar) at the limiting low-pressure, the limiting high-pressure, as well as the intermediate fall-off ranges. The results show that published experimental rate constants for methyl dissociation correspond to the fall-off region close to the low-pressure limit. At the low-pressure limit the activation energy is less than the bond dissociation energy, in agreement with experimental results. Forward and backward rate coefficients at the high-pressure limit are compared with other theoretical calculations. More theoretical and experimental work is necessary to understand the reverse reaction and its competing reactions, as well as the decomposition channel leading to CH + H2. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550260116
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  • 7
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    Super-resolution chromatin tracing reveals domains and cooperative interactions in single cells (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-10-26
    Description: The spatial organization of chromatin is pivotal for regulating genome functions. We report an imaging method for tracing chromatin organization with kilobase- and nanometer-scale resolution, unveiling chromatin conformation across topologically associating domains (TADs) in thousands of individual cells. Our imaging data revealed TAD-like structures with globular conformation and sharp domain boundaries in single cells. The boundaries varied from cell to cell, occurring with nonzero probabilities at all genomic positions but preferentially at CCCTC-binding factor (CTCF)- and cohesin-binding sites. Notably, cohesin depletion, which abolished TADs at the population-average level, did not diminish TAD-like structures in single cells but eliminated preferential domain boundary positions. Moreover, we observed widespread, cooperative, multiway chromatin interactions, which remained after cohesin depletion. These results provide critical insight into the mechanisms underlying chromatin domain and hub formation.
    Keywords: Biochemistry, Cell Biology, Online Only
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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    PAPER CURRENT
  • 8
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    Acceleration of electrons and ions by strong lower-hybrid turbulence in solar flares (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: One of the outstanding problems in solar flare theory is how to explain the 10-20 keV and greater hard x-ray emissions by a thick target bremsstrahlung model. The model requires the acceleration mechanism to accelerate approximately 10(exp 35) electrons sec(exp -l) with comparable energies, without producing a large return current which persists for long time scales after the beam ceases to exist due to Lenz's law, thereby, producing a self-magnetic field of order a few mega-Gauss. In this paper, we investigate particle acceleration resulting from the relaxation of unstable ion ring distributions, producing strong wave activity at the lower hybrid frequency. It is shown that strong lower hybrid wave turbulence collapses in configuration space producing density cavities containing intense electrostatic lower hybrid wave activity. The collapse of these intense nonlinear wave packets saturate by particle acceleration producing energetic electron and ion tails. There are several mechanisms whereby unstable ion distributions could be formed in the solar atmosphere, including reflection at perpendicular shocks, tearing modes, and loss cone depletion. Numerical simulations of ion ring relaxation processes, obtained using a 2 1/2-D fully electromagnetic, relativistic particle in cell code are discussed. We apply the results to the problem of explaining energetic particle production in solar flares. The results show the simultaneous acceleration of both electrons and ions to very high energies: electrons are accelerated to energies in the range 10-500 keV, while ions are accelerated to energies of the order of MeVs, giving rise to x-ray emission and gamma-ray emission respectively. Our simulations also show wave generation at the electron cyclotron frequency. We suggest that these waves are the solar millisecond radio spikes. The strong turbulence collapse process leads to a highly filamented plasma producing many localized regions for particle acceleration and resulting in approximately 10(exp 17) electron 'beamlets' of width approximately equal to 10 lambda sub De which eliminates the production of large magnetic fields. In this paper, we demonstrate that the model produces an energetic electron spectrum with the right flux to account for the hard x-ray observations.
    Keywords: SOLAR PHYSICS
    Type: NASA-TM-109723 , NAS 1.15:109723 , RAL-94-022
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Lower hybrid resonance acceleration of electrons and ions in solar flares and the associated microwave emission (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The particle acceleration processes here studied are driven by the relaxation of unstable ion ring distributions; these produce strong wave activity at the lower hybrid resonance frequency which collapses, and forms energetic electron and ion tails. The results obtained are applied to the problem posed by the production of energetic particles by solar flares. The numerical simulation results thus obtained by a 2 1/2-dimensional particle-in-cell code show a simultaneous acceleration of electrons to 10-500 keV energies, and of ions to as much as the 1 MeV range; the energy of the latter is still insufficient to account for gamma-ray emission in the 4-6 MeV range, but furnish a seed population for further acceleration.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 409; 1; p. 465-475.
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Simulation studies of electron acceleration by ion ring distributions in solar flares (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A 2.5-dimensional fully relativistic EM, particle-in-cell code (PIC) is used to investigate a potential electron acceleration mechanism in solar flares. The free energy is provided by ions which have a ring velocity distribution about the magnetic-field direction. Ion rings may be produced by perpendicular shocks, which could in turn be generated by the super-Alfvenic motion of magnetic flux tubes emerging from the photosphere or by coronal mass ejections. Such ion distributions are known to be unstable to the generation of lower hybrid waves, which have phase velocities in excess of the electron thermal speed parallel to the field and can, therefore, resonantly accelerate electrons in that direction. The simulations show the transfer of perpendicular ion energy to energetic electrons via lower hybrid wave turbulence. With plausible ion ring velocities, the process can account for the observationally inferred fluxes and energies of non-thermal electrons during the impulsive phase of flares.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 130; 229-241
    Format: text
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    NASA TECHNICAL REPORTS
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