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  • 1
    Electronic Resource
    Electronic Resource
    Photoinduced molecular transformations. Part 107. A versatile substitution of a carbonyl group of steroidal ketones by a heteroatom. The synthesis of aza-, oxa-, thia-, selena-, and tellurasteroids (1990)
    s.l. : American Chemical Society
    The @journal of organic chemistry 55 (1990), S. 2170-2176 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00294a035
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of defect scattering on guided electron waves in two coupled quantum wires (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2299-2311 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated how the presence of a defect in two coupled quasi-one-dimensional quantum wires influences the propagation properties of guided electron waves in the system. The defect potential in the two dimensional electron gas is modeled by a two dimensional δ function. In elastic scattering, the transfer of the electron among various eigenstates of the uncoupled quantum wires and from one wire to the other is largely affected by the defect potential. For the single mode shallow potential well system, the defect causes incomplete energy transfer between the channels. As the position of the defect varies along the channel, the characteristics of the mode amplitude functions change dramatically as the defect passes through nodes of the amplitude function of the incident waves in the channel. When the defect position is away from these nodes the amplitude functions of the transmitted waves reduce greatly due to the large reflection by the defect. And their variation never reaches zero as in the case without defect. When the defect position is near these nodes the tunneling characteristics between the two channels are as if the defect is absent since the reflection is minimal. For the strong scatterer we find a pinning effect in that the mode amplitude function of the channel where the defect is located always has one of its transmission minima pinned down to the defect. We introduce a possible way of injecting the propagating electron into a particular channel and at a given longitudinal position, by controlling the position of the defect in the structure. In the multimode deep potential well structure, the transfer from an eigenstate of the uncoupled quantum wires to the other states is greatly enhanced and the characteristics of the amplitude functions are dramatically changed by intersubband scatterings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351572
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  • 3
    Electronic Resource
    Electronic Resource
    The first-order Jahn–Teller distortion and the symmetry of the electron density in the BH+3 radical (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 1232-1239 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Self-consistent field (SCF) and complete active space multiconfiguration (CAS-MCSCF) calculations with extended basis sets are used to show that the electron–nuclear attraction energy is the dominant contributor to the total energy lowering associated with the Jahn–Teller distortion of BH+3. Furthermore the Jahn–Teller distortion raises the interelectronic and internuclear repulsion energies. These observations are consistent with a contraction of the molecular framework and electron cloud. In the context of the relationship between the electron distribution and the Jahn–Teller distortion direction, it is observed that the electron density associated with the canonical highest occupied molecular orbital (HOMO) of the D3h constrained BH3 radical has C2v symmetry, which corresponds to the preferred point group of the Jahn–Teller distortion in BH+3. The effect of electron correlation on the electron density distribution is shown to be inconsequential for the prediction of the direction of the Jahn–Teller distortion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462873
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  • 4
    Electronic Resource
    Electronic Resource
    Application of the thermodynamic cycle perturbation method to systems with nonadditive potentials (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2762-2768 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have extended the thermodynamic perturbation cycle approach to compute thermodynamic properties of systems with nonadditive potentials. A rapid iterative method was developed and tested by application to systems of water microclusters of alkali metal cations and halogen anions interacting by means of a model potential incorporating polarization. The perturbation cycle calculations are in agreement with the results of direct calculation as long as both initial and final microclusters are unambiguously stable. For marginally stable cationic microclusters, e.g. Rb(H2O)+6 or Cs(H2O)+5, the perturbation cycle approach appears to provide more reliable estimates of thermodynamic properties. Transmutation entropy estimates entail substantial uncertainty, even for transitions between stable microclusters. They are in fair agreement with those of other theoretical studies but differ noticeably from the experimental values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458915
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  • 5
    Electronic Resource
    Electronic Resource
    Wetting transitions in polymer blends: A Monte Carlo lattice simulation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8537-8541 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Wetting transitions of binary polymer mixtures in contact with a wall were studied using lattice models by the method of Monte Carlo simulation. First-order wetting transitions were found below the critical temperature but at a moderately high volume fraction of the polymer type favored by the wall. The transitions appear to be second order at low temperatures or for short chain lengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460087
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic conductance of mesoscopic waveguides (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1777-1782 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a theoretical investigation of dynamic conductance G(ω), for general ac frequency ω, of two-dimensional mesoscopic waveguides whose transport is characterized by antiresonances. We calculate G(ω) by numerically evaluating nonequilibrium Green's functions. By tuning the ac frequency we observe photon-assisted resonant transport as well as a gradual smearing out of the antiresonances. The antiresonance causes the dynamic response to vary between capacitive-like behavior to that of the inductive-like behavior. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337086
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  • 7
    Electronic Resource
    Electronic Resource
    The role of amorphous Ni50P50 precoating layer in CoCrPtTa thin film media (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6346-6348 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of amorphous Ni50P50 as a precoating layer in CoCrPtTa/Cr/glass substrate thin film media has been studied. It was found that the amorphous NiP layer has a strong effect on grain size reduction. Both in-plane transmission electron spectroscopy (TEM) images and atomic force microscopy images reveal a large reduction of the average grain size of the Cr underlayer deposited on the precoating Ni50P50 layer compared to the one on a glass substrate. The TEM images also show that Ni50P50 film has isolated unique granular features approximately 10 nm in diameter, consisting of grains with uniform size that could be inherited by the subsequent layers. Samples with NiP precoating layer on the glass substrate show a slightly higher surface roughness that may be attributed to the smaller Co grains induced. Magnetic force microscopy images at remanent state also indicate a much smoother micromagnetic structure for media with a NiP precoating layer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372701
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  • 8
    Electronic Resource
    Electronic Resource
    Co alloy longitudinal thin film media with ultrahigh coercivity (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6352-6354 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of CoCrTa intermediate layer and postannealing on the magnetic properties and microstructure of CoCrPt/Cr thin film media has been investigated. Through a postdeposition annealing in a vacuum oven, a tremendous increase of coercivity up to 6000 Oe was observed for these CoCrPt/CoCrTa/Cr films, in which the thickness of CoCrTa intermediate layer is about 2.6 mm. X-ray diffraction results showed that the hexagonal-close-packed crystallographic structure for the cobalt alloy did not show any change for the sample after postannealing. In-plane transmission electron microscope images for the CoCrPt/CoCrTa/Cr films showed no change of the morphology before and after annealing and about 15% increase of the grain size for the films after annealing. Delta M curves and remanent squareness results showed that intergrain diffusion may result in this improvement of magnetic properties. Atomic force microscope images showed that the surface roughness for the sample after annealing was almost the same as that before annealing. After tailoring the thickness of the magnetic layer to 10 nm, the coercivity as high as 5200 Oe and Mrt value as low as 0.24 memu/cm2 were obtained, which may support ultrahigh bit density than current media. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372703
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  • 9
    Electronic Resource
    Electronic Resource
    Improvement of giant magnetoresistance performance of a metal layered structure (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6394-6396 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A metal layered structure consisting of Cr/Cu buffer layer and two Co layers with different thickness, separated by a Cu spacer, was deposited on Si wafers using magnetron sputtering. The influence of the individual layer's thickness on the magneto transport and magnetic hysteresis was studied. Optimization of the magnetoresistance performance was supported by the current in-plane giant magnetoresistance (GMR) modeling based on the solution to the Boltzmann transport equation. The best structures demonstrated very sharp magnetization reversal of the lower Co layer at about 100 Oe accompanied by resistivity change with a rate of 0.9%/Oe. Maximum GMR effect measured at 5 K was 9.6%. Samples with capping layers exhibited substantially smaller switching fields of the upper Co layer than the uncapped samples with a minute amount of CoO. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372717
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrahigh coercivity of granular CoCrPt–SiO2 thin films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6971-6973 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic properties and microstructure of granular CoCrPt–SiO2 thin films with Cr underlayers have been investigated for potential applications in magnetic recording media. The coercivities exceeding 2500 Oe have been obtained in the as-deposited films with SiO2 varied from 8 to 16 vol %. Remarkable improvement in magnetic properties was achieved by postdeposition annealing in vacuum. The ultrahigh coercivity up to 5640 Oe was obtained in the lower SiO2 content film (CoCrPt)96(SiO2)4 which was annealed at 580 °C for 10 min. The annealing did not induce significant grain growth. The average grain size varied from 10 to 20 nm, depending on SiO2 concentration. Grain isolation in magnetic layer was achieved by the segregated SiO2 and further enhanced by annealing. The ac demagnetized magnetic clusters, observed by magnetic force microscopy, became very fine after annealing. The peak value of delta M curves changed from positive to negative value, indicating a great reduction of intergrain magnetic exchange coupling after annealing. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372903
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