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  • 1990-1994  (8)
  • 1993  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Application of microwave detection of the Shubnikov–de Haas effect in two-dimensional systems (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7533-7542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave detection of the Shubnikov–de Haas (SdH) effect as a contact-free characterization technique for different types of two-dimensional semiconductor structures is explored in the low magnetic field region. The detection technique and the data analysis are described. The character and relevance of the single-particle relaxation time that can be detected by this technique are distinguished from the usual transport scattering time. The measured values of the carrier concentration and single-particle relaxation time agree with electrical measurements, while the problem of making contacts on the structure is avoided. Uncertainties in the analysis for the single-particle relaxation time are discussed. Cyclotron resonance, optically detected cyclotron resonance, and magneto-photoluminescence are applied as other contact-free techniques on the same samples. The results and suitability of these techniques are compared with the microwave detection of the SdH effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354001
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On the time scale and time course of protein conformational changes (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7253-7259 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Proteins change their global conformation very slowly compared to the time scales of most localized internal motion. The relationship between these slow and fast processes was investigated with the aid of a stochastic model recently applied to a related problem of protein folding [Zwanzig et al., Proc. Natl. Acad. Sci. 89, 20 (1992)]. In the present study a change in conformation was treated as a bond rotational isomerization that may only occur when several other gating bonds simultaneously assume permissive orientations. The requirement of correct orientation of these gating bonds is analogous to the alignment of the tumblers in a lock. For a range of reasonable choices of parameters, this model generated realistic time scales for protein conformational changes. Although the transition time depended on the value of an energy bias against the permissive position of a gating bond, the model could still generate reasonable transition times in the absence of an energy bias. For a wide range of parameters chosen to give typical experimental rates for biological transitions, the model predicted conformational changes with simple exponential kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465418
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Composition dependence of the in-plane effective mass in lattice-mismatched, strained Ga1−xInxAs/InP single quantum wells (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 657-659 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The composition dependence of the in-plane conduction band effective mass in strained 15-nm-thick lattice-mismatched Ga1−xInxAs/InP single quantum wells was determined by conventional cyclotron and optically detected cyclotron resonance techniques. Our results are in agreement with a self-consistent calculation taking into account effects due to nonparabolicity, confinement, strain, and finite two-dimensional carrier densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109948
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Electron spin resonance investigations of oxidized porous silicon (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1930-1932 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The defect properties of rapidly thermally oxidized porous silicon are studied by electron paramagnetic resonance. Two different types of defects can be distinguished. One is very similar to the defects observed in damaged crystalline or amorphous Si, whereas the second one is closely related to the Pb center. A maximum defect density of 8×1018 cm−3 is observed for samples annealed at about 600 °C. The intensity of the photoluminescence band at 1.7 eV anticorrelates with the density of the defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110652
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Defects in porous silicon investigated by optically detected and by electron paramagnetic resonance techniques (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2120-2122 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The defect properties of as-etched and annealed porous silicon are studied by electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR). The paramagnetic defect observed is closely related to the Pb0 center at the Si/SiO2 interface. In EPR a minimum defect density of 1016 cm−3 is observed for the as-etched silicon, which reaches a maximum of 8×1018 cm−3 for samples annealed at about 400 °C. In the ODMR experiments, the same dangling bond center is observed on the 1.5 eV luminescence band enhancing the luminescence—but with increased sensitivity and as a decrease of the emission intensity in the infrared emission band at 1 eV of porous silicon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110559
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  • 6
    Electronic Resource
    Electronic Resource
    Carrier-modulated, microwave-detected Shubnikov–de Haas oscillations in two-dimensional systems (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2725-2727 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It was recently shown that Shubnikov–de Haas (SdH) oscillations observed in conventional resistance measurements can be dramatically enhanced by light-induced carrier modulation [S. E. Schacham, E. J. Haugland, and S. A. Alterovitz, Appl. Phys. Lett. 61, 551 (1992)]. Here we report on a similar observation in the case of contact-free, microwave-detected SdH oscillations. In the original version of this nondestructive technique [P. Omling, B. Meyer, and P. Emanuelsson, Appl. Phys. Lett. 58, 931 (1991)], magnetic-field modulation was applied in order to enhance the sensitivity. If, instead, the carrier concentration is modulated by illumination, we show that a similar enhancement in the sensitivity of the signal is obtained. We demonstrate that very simple microwave equipment can be used for the measurements, and that the accessible magnetic-field region can be extended, allowing for contact-free transport investigations in the high magnetic-field region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109245
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    Paper (German National Licenses)
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  • 7
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    Christus Faber (Book Review) (1993)
    Woodstock, Md., etc : Periodicals Archive Online (PAO)
    Theological Studies. 54:3 (1993:Sept.) 552 
    Details
    ISSN: 0040-5639
    Topics: Theology and Religious Studies
    Notes: BOOK REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:3258-1993-054-03-000008
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  • 8
    Electronic Resource
    Electronic Resource
    Low-dose interferon in chronic hepatitis non-A/non-B: effects on quantitative liver function and structure in a randomized, controlled multicenter trial (1993)
    Springer
    Journal of molecular medicine 71 (1993), S. 888-893 
    Details
    ISSN: 1432-1440
    Keywords: Hepatitis C virus RNA ; Polymerase chain reaction ; Quantitative liver function ; Galactose elimination capacity ; Randomized controlled trial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In this randomized, controlled multicenter trial we evaluated the effects of recombinant interferon-α2b on galactose elimination capacity and histological activity index in 88 patients with chronic active hepatitis non-A/non-B. Forty-five patients were randomly assigned to treatment with interferon at 1.5 × 106 U three times per for 1 year; 43 patients were assigned to no treatment. A complete response (normalization of alanine aminotransferase) was observed, respectively, in 47% and 5% of the two groups (P〈0.006); 47% of these patients suffered a relapse. Thus 22% of patients had a sustained response. Histological activity decreased significantly in responders (P〈0.04) while the biopsy score did not change significantly in nonresponders. In contrast, galactose elimination capacity — a surrogate marker for survival in chronic active hepatitis — was not affected by response to treatment. None of the parameters evaluated, including hepatitis C virus RNA, was able to predict response or relapse. We conclude that low-dose interferon treatment for 1 year is as effective as the recommended treatment schedule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185598
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    Paper (German National Licenses)
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