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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1790-1792 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented to show that the hydrostatic strain in a metastable Al0.3Ga0.7As film grown at low temperatures induces a one-dimensional compositional modulation upon annealing at 600 °C, a direct evidence of the existence of a miscibility gap in strained AlxGa1−xAs. A strain-driven vacancy-assisted mechanism is proposed to account for the compositional modulation and segregation of As clusters. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Long range composition ordering and spontaneous formation of Al rich and Ga rich AlxGa1−xAs/AlyGa1−yAs superlattice were demonstrated. This was observed by cross-sectional transmission electron microscopy (TEM) in a 280 A(ring) Al0.4GaAs quantum well laser diode heterostructure with Al0.7GaAs barriers grown on (111)B GaAs substrates. On the contrary, none of above superstructure was observed by TEM on a side-by-side grown (100) oriented substrate. More evidence is shown in the (111)B Al0.7GaAs barriers which were disordered due to a high growth temperature and did not show any superstructure. 10 K photoluminescence was shown with 32 meV redshift and a 12-times peak intensity enhancement in (111)B orientation. © 1994 American Institue of Physics.
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  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low temperature InGaAs strained quantum wells have been grown by molecular beam epitaxy and annealed at 600–900 °C for 10 min. For an optimized annealing condition, arsenic precipitates can be successfully confined in the InGaAs wells and completely depleted in the GaAs barriers. The strong accumulation of As precipitates shows that the phenomena are not due to the strain effect but may be explained by the difference of interfacial energy between precipitate and matrix. The ability to control the As precipitates into two-dimensional quantum wells in LT materials has unique applications in a wide variety of devices.
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Smooth, c-axis oriented, superconducting thin films of YBa2Cu3O7−x and DyBa2Cu3O7−x have been grown on (100) MgO by organometallic molecular-beam epitaxy. To our knowledge this is the first report of this technique for the fabrication of this class of high Tc superconductors. Y (or Dy) β-diketonate organometallic sources are utilized with Ba and Cu metallic sources. Films are grown in situ by codepositing from these sources in an ozone ambient with a substrate temperature of 700 °C. The use of an active oxygen source (ozone) is required for decomposition of the organometallic sources as well as for the attainment of superconducting films in situ. The films are characterized by Tc's as high as 85 K and Jc's of 1.2×106 A/cm2 at 12 K and 2.4×103 A/cm2 at 77 K. In addition to the four point Tc and Jc results, alternating-current susceptibility measurements are also reported. The composition of the films has been determined by Rutherford backscattering spectroscopy, Auger and secondary ion mass spectroscopy analysis, with the smoothness of the films characterized by scanning tunneling microscopy.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 626-628 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stimulated emission from a clearly defined quantum well transition has been observed from single quantum wells as thin as two monolayers (ML, 1 ML=2.83 A(ring)). These results are unexpected since previous experimental and theoretical work has indicated that if the well width Lz is smaller than the scattering path length of electrons or holes, carrier collection becomes inefficient and the quantum well cannot support stimulated emission. Laser thresholds of these separate confinement, single quantum well samples are quite low, despite the fact that these ultrathin quantum wells are undoped and do not have graded band-gap confining layers. These unexpected results can be explained in terms of the spatial extent of the wave function rather than the well thickness.
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spontaneous and stimulated emission from a series of Al0.7Ga0.3As -Al0.49Ga0.51As-GaAs ultrathin single [1,2, and 3 monolayer (ML), 1 ML=2.83 A(ring)] and multiple (2 ML) quantum well separate confinement heterostructures are demonstrated and compared to a control sample (0 ML). Spectra from sample to sample are very different and depend on the alignment of the n=1, Γ electron bound state in the quantum well with the Xminima (lowest band edge) in the indirect-gap (Al0.49Ga0.51As) confining layers. Some samples (3 ML single and 2 ML multiple quantum well) can support stimulated emission despite the fact that the quantum well is undoped, unstrained, and very thin (Lz (very-much-less-than)scattering path length) and that most of the wave function is in the indirect-gap confining layers. These experimental results can be explained using a simple model based on the spatial extent of the wave function (rather than the well width) under the special condition of band alignment between the Γ and X states.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1853-1855 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spontaneous and stimulated emission spectra from a series of AlxGa1−xAs-GaAs single quantum well heterostructures are demonstrated for well widths as thin as 20 A(ring). These undoped samples, grown by molecular beam epitaxy, are the thinnest single quantum wells ever reported to support stimulated emission. Laser thresholds are generally quite low (1.2 kW/cm2) despite the fact that the single well is undoped and of dimensions which were previously thought to be too small to effectively collect excess carriers (Lz(very-much-less-than)scattering path length). A simple model based on the spatial extent of the wave function, rather than the well width, is proposed to explain the experimental results.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 215-217 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first continuous wave room-temperature InGaAs-GaAs-AlGaAs strained-layer semiconductor laser diode grown by molecular beam epitaxy. The laser is a multiple quantum well transverse junction stripe laser with a lateral heterojunction fabricated by zinc diffusion enhanced compositional disordering. The low-threshold (20 mA) and single-mode performance of the laser demonstrates that a high-quality lateral p+-p-n junction and lateral heterobarrier can be formed by zinc diffusion compositional disordering of a strained-layer InGaAs-GaAs-AlGaAs quantum well heterostructure.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background The aetiology of food allergy remains unclear. Although failure to develop or breakdown in oral tolerance has been proposed, the existence of physiologic sensitization routes other than the gastrointestinal tract cannot be excluded.Objective The purpose of this study is to clarify whether or not exposure to allergen through the skin can promote food allergy.Methods BALB/c mice were shaved on the back, and a patch impregnated with 100 μg of ovalbumin (OVA) was applied to the dorsal skin for a 1-week period and then removed. After three courses of sensitization, OVA-specific antibodies in sera were measured, and then mice were orally challenged with 50 mg of OVA. Anaphylactic symptoms, plasma histamine levels, and histology of intestines and lungs after oral challenge were examined.Results Epicutaneous (EC) sensitization of mice to OVA induced a high level of OVA-specific IgE. Subsequent oral challenge with OVA resulted in symptoms of systemic anaphylaxis with elevated levels of plasma histamine as well as histological changes in both intestines and lungs. In the presence of anti-IL-4 antibodies, EC sensitization failed to provoke an IgE response, but still induced a Th2-predominant cellular immune response in lungs after oral challenge.Conclusion We demonstrated for the first time that food allergy can be induced by allergen exposure through the skin. Our results identify a novel role of EC sensitization in the pathogenesis of food allergy.
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  • 10
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Food allergy is a common disease without effective treatment. Since strict elimination of food allergens may be difficult, strategies for effective intervention are urgently needed.Objective  The aim was to investigate the prophylactic use of orally administrated FIP-fve, an immunomodulatory protein isolated from the edible mushroom Flammulina velutipes, in a murine model of food allergy.Methods BALB/c mice were immunized twice intraperitoneally with ovalbumin (OVA), at an interval of 2 weeks. Before and during each period of immunization, FIP-fve (200 μg per mouse) or phosphate-buffered saline was given orally every other day with a total of five doses. Then OVA-specific antibodies and cytokine profiles were determined. Subsequently, the mice were orally challenged with OVA. Symptoms of anaphylaxis, levels of plasma histamine, and histology of intestines were examined.Results Mice receiving oral FIP-fve treatment during sensitization to OVA had an impaired OVA-specific IgE response with a Th1-predominant cytokine profile. These mice were protected from systemic anaphylaxis-like symptoms induced by subsequent oral challenge with OVA.Conclusion Oral administration of FIP-fve has a Th1-skewing effect on the development of the allergen-specific immune response, and may serve the purpose of immunoprophylaxis for food allergy and other allergic diseases.
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