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  • 1985-1989  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Theory of homogeneous nucleation: A chemical kinetic view (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 416-423 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In classical theory of homogeneous nucleation the flux is derived initially as a function of rate constants for the condensation and vaporization reactions of clusters in the kinetic path. The evaluation of the vaporization rate for clusters of different size is provided by the Thomson–Gibbs relation. In view of discrepancies still existing between measurements and theoretical predictions and the continuing reservations on applying TG relation to microscopic size clusters a different approach is proposed in the present work. A simple function with two undetermined parameters has been used in place of the TR relation to relate the activation energy of the vaporization reaction to cluster size. The parameters are iterated to assume optimum values in numerical computation so experimental data may be correlated. Calculations show this approach closely predicts and correlates available data for water, benzene, and ethanol. The nucleation formulism is redeveloped with an emphasis on the chemical kinetic view. Surface tension of the liquid and free energy of droplet formation are not used in its derivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450154
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  • 2
    Electronic Resource
    Electronic Resource
    Interface properties of HgCdTe metal-insulator-semiconductor capacitors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 265-267 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The conductance method has been used to measure the density of interface states of the ZnS/Hg0.775Cd0.225Te metal-insulator-semiconductor (MIS) system with three different HgCdTe surface treatments. It is found that the density of fast interface states increases from ∼1011 eV−1 cm−2 at the conduction-band minimum to ∼1013 eV−1 cm−2 near the valence-band maximum. In addition, the interface states located in the lower part of the band gap communicate with the valence band so efficiently that the effective band gap is reduced. Our observations explain why the p-type MIS photodiode is superior to the n-type version in terms of breakdown voltage and storage time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100985
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    New field-effect resonant tunneling transistor: Observation of oscillatory transconductance (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2742-2744 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present device characteristics of a field-effect, unipolar, resonant tunneling transistor. An oscillatory tunneling current in the transfer characteristics is observed for the first time. Our observation confirms a recent hypothesis that a mere three-to-two dimensional resonant tunneling can occur when scattering rate is less than the attempt frequency of tunneling electrons in the quantum well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101940
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  • 4
    Electronic Resource
    Electronic Resource
    Implant and annealed ohmic contact to a thin quantum well (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1650-1652 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate for the first time that ion implantation and implant activation annealing, combined with a heavily doped InGaAs surface layer, can be used to make nonalloying shallow ohmic contact to an n-type InGaAs (or GaAs) quantum well. Quantum Hall effect and Shubnikov–de Haas oscillations are clearly observed, which indicates that electrons in the quantum well remain two dimensional despite the post-implantation high-temperature annealing. This technique can be applied to devices that would need to make shallow ohmic contact to a thin (∼100 A(ring) or less) quantum well, where existing selective etching approaches fail to work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102227
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  • 5
    Electronic Resource
    Electronic Resource
    Adhesion and deformation of metal/polyimide layered structures (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1911-1917 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Adhesion and interfacial failure of Cr, Cu, and Cu/Cr films on a thin pyromellitic dianhydride-oxydianiline polyimide substrate have been investigated using a recently developed stretch deformation technique. This method directly measures the energy required to separate the interface from the difference in the load versus elongation curves between film/substrate and substrate structures. The failure mode was observed in combination with morphological studies by in situ optical microscopy and scanning and transmission electron microscopies. The stress distribution in the sample upon stretching has been computed by a finite element analysis. The difference in the stress relief modes, film fracture, and delamination behavior for Cu versus Cr films is discussed. The important role of crack formation in the metal overlayer for initiating failure is demonstrated. The effects due to the addition of a brittle Cr interface layer between polyimide and Cu on the buildup of stress and the onset of failure have also been investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342903
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  • 6
    Electronic Resource
    Electronic Resource
    Stress relaxation during thermal cycling in metal/polyimide layered films (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6690-6698 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stress relaxation behavior during thermal cycling of metal/quartz and metal/polyimide/quartz layered structures has been investigated using a cantilever bending beam technique. The metals chosen for this study include Cu and Cr, two materials with contrasting mechanical and interfacial bonding properties. A finite element analysis, as well as an analytical calculation, has been carried out to deduce the stress distribution in the layered structures. Results indicate that the extent of stress relaxation strongly depends on the intrinsic mechanical property of the metal film with significantly higher stresses residing in the Cr film than in the Cu film. The interfacial polyimide layer has been found to serve as an effective buffering layer to reduce the residual stress in metal films. Observations from transmission electron microscopy suggest that the stress is partially released through the deformation of the polyimide near the metal/polyimide interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341999
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  • 7
    Electronic Resource
    Electronic Resource
    Photoluminescence from the two-dimensional electron gas at GaAs/AlGaAs single heterojunctions (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 285-287 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied photoluminescence from GaAs/Al0.3Ga0.7 As modulation-doped single heterojunctions, using excitation sources from infrared to ultraviolet near-liquid-helium temperature. The spectra have a strong interface component, accompanied by bulk GaAs and AlGaAs band-gap luminescence. Using ultraviolet instead of infrared as the excitation, the interface signal is greatly enhanced relative to the bulk GaAs luminescence. The interface signal can be shifted to the higher energies when a semitransparent front gate is positively biased. Our observations indicate that the interface luminescence comes from the recombination of the two-dimensional electrons with holes trapped at or near the interface. The peaks and the shoulders in the interface spectra appear to correspond to subbands of the two-dimensional electron gas at the interface. Our results demonstrate the feasibility of doing spectroscopic studies on high-mobility electrons at single heterojunctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99915
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of ion implantation on the microstructure of oxide scales formed on a 20Cr/25Ni/Nb-stabilized stainless steel in carbon dioxide at 825° C (1987)
    Springer
    Journal of materials science 22 (1987), S. 449-458 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Specimens of a stainless steel (20%Cr, 25%Ni stabilized with niobium and also containing 0.9% Mn and 0.6% Si) implanted with lanthanum to a dose of 1017 ion cm−2 , together with unimplanted specimens, have been oxidized in carbon dioxide at 825° C for times up to 9735 h. Transverse sections through the oxide scales formed on the respective specimens have been studied by analytical electron microscopy. After this exposure the scale on the unimplanted 20/25/Nb stainless steel consists of an outer, large-grained, spinel layer, a middle fine-grained Cr2O3 layer and an inner, discontinuous silicon rich, niobium and chromium bearing, amorphous layer. The main effects of the lanthanum implantation are to improve oxidation resistance and maintain scale adherence during thermal cycling. The microstructural changes in the scale formed on the lanthanum implanted 20/25/Nb steel include finer Cr2O3 oxide grains and an intermediate region between the outer spinel and inner Cr2O3 layers comprised of both oxides. The lanthanum concentrates in this region and appears to act as a marker due to its low diffusivity. Mechanisms of scale development on the 20/25/Nb stainless Red and the influence of lanthanum implantation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160752
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  • 9
    Electronic Resource
    Electronic Resource
    Markedly altered membrane transport and intracellular binding of vincristine in multidrug-resistant Chinese hamster cells selected for resistance to vinca alkaloids (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 126 (1986), S. 266-274 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Studies of a multidrug-resistant variant (DC-3F/VCRd-5L) of Chinese hamster lung cells selected for resistance to vinca alkaloids revealed marked alterations in transport and intracellular binding of [3H]vincristine compared to parental DC-3F cells. Influx of [3H]vincristine in DC-3F cells appears to be an equilibrating, but mediated, process. Although saturation kinetics for [3H]vincristine influx were not demonstrated, an extremely high temperature-dependence (Q1027-37°C = 5-6) and trans-inhibition of influx following preloading of cells with nonradioactive vincristine argue in favor of a carrier-mediated process. Efflux of [3H]vincristine from parental cells conformed to first-order kinetics (t1/2 37° = 3.6 ± 0.4) and exhibited a lower temperature-dependence (Q10 27-37°C = 3-3.5) than influx. In variant vs. parental cells, influx of [3H]vincristine was reduced 24-fold and efflux was increased twofold, accounting for the large (approximately 48-fold) reduction in steady-state level of exchangeable drug accumulating in variant cells. Otherwise, transport of [3H] vincristine in these cells showed characteristics similar to parental DC 3F cells. Also, the rate and amount of intracellular binding of [3H]vincristine in variant cells was almost 40-fold lower than in parental cells. These alterations in influx and efflux of [3H]vincristine and its intracellular binding appear to account, at least to a major extent, for the high level of resistance (2,750-fold) of this variant to vinca alkaloids. In contrast, cross-resistance of this variant to daunomycin (178-fold) could be explained only minimally by a transport alteration. Only a two-fold increase in efflux of [3H]daunomycin was demonstrated in variant vs. parental cells along with some decrease in intra-cellular binding. Influx of [3 H]daunomycin was unaltered. In view of these results, we conclude that these two agents most likely do not share the same route for entry in these cells but might share the same efflux route.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041260217
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  • 10
    Electronic Resource
    Electronic Resource
    Altered molecular properties of tubulin in a multidrug-resistant variant of Chinese hamster cells selected for resistance to vinca alkaloids (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 136 (1988), S. 341-347 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The basis for the markedly altered intracellular binding of [3H]vincristine in a multidrug-resistant variant (DC-3F/VCRd-5L) of Chinese hamster lung cells (DC-3F) was investigated. Binding of [3H]vincristine by protein in cytosol derived from each cell type exhibited a differing requirement for GTP in MgCl2 containing buffer of low-ionic strength. Binding of [3H]vincristine occurred to cytosolic protein derived from both variant and parental DC-3F cells, but after removal of GTP, binding only occurred to cytosolic protein from parental cells regardless of the presence of added GTP. Although binding by cytosolic protein from parental DC-3F cells did not require GTP, the addition of 0.1 mM GTP increased by two-fold the rate and extent of binding. When cytosol from variant and parental DC-3F cells was incubated with low concentrations of [3H]vincristine in high-ionic strength buffer and analyzed by molecular-sieve HPLC, most of the protein binding [3H]vincristine in parentally derived cytosol eluted as Mr 110,000-115,000 daltons, corresponding to that for dimeric tubulin. The same binding species was not detected in cytosol derived from variant cells. However, these same fractions derived with both parental and variant cytosols contained tubulin as shown by SDS-PAGE and immunoblotting. A smaller peak of [3H]vincristine binding and an amount of tubulin equal to that found in later fractions were found in the void volume during the same HPLC elution runs with cytosol from both variant and parental DC-3F cells. Evidence was also obtained for differences between parental and variant DC-3F cells in β-tubulin isoforms following isoelectric focusing and immunoblotting. Parental-cell cytosol contains a single isoform of β-tubulin. However, in variant cell cytosol the same isoform and, in addition, three more basic isoforms were found. These alterations in [3H]vincristine binding and in isoform compositions of β-tubulin in variant versus parental DC-3F cells may have importance in regard to vincristine resistance in DC-3F cells.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041360218
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