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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 229-233 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A computer simulation based on the binary collision approximation has been performed to investigate the Si implantation efficiency, the Si depth profile, and the vacancy formation for Si-implanted GaAs (001) crystals. The results reveal a strong dependence on the incident angle of the Si source. The calculated depth profile of Si agrees well with the experimental results from secondary-ion mass spectroscopy. The simulated distribution of vacancies is shallower than that of Si atoms. Also, the calculated number of Ga vacancies exceeds that of As vacancies, which suggests that the Si atoms easily occupy the Ga sites and are activated as donors.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1959-1961 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface chemical properties of a GaAs layer grown by molecular beam epitaxy were investigated by photoluminescence (PL) and photoreflectance (PR) measurements. While the intensity of the PL spectra for the sulfur-treated GaAs, using a (NH4)2Sx solution, increased 75 times compared to that for the as-grown GaAs, the peaks for the as-grown GaAs measured by PR vanished after a sulfur treatment. These results indicate that the surface state acting as the nonradiative recombination centers was passivated by the sulfur. The chemical adsorption behavior resulting from the sulfur is discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0428
    Keywords: Atherosclerosis ; cell death ; cell mitosis ; endothelium ; Evans blue-albumin ; permeability ; streptozotocin diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Hypertension, cigarette smoking and diabetes mellitus are well-known risk factors for atherosclerosis and coronary heart disease. Repeated endothelial cell injury and increased lipid entry have been suggested as initiating events in atherogenesis. Our previous studies have demonstrated that the frequency of endothelial cell death and associated endothelial permeability were significantly increased in the aorta of spontaneously hypertensive rats and chronic oral nicotine-treated rats. In the present investigation, we examined the hypothesis that diabetes also increases the frequency of arterial endothelial cell death and hence transendothelial macromolecular transport, which may have some implications in increasing lipid entry and thus accelerating atherogenesis. Diabetes was induced in 15 male Sprague-Dawley rats by intraperitoneal injection of 60 mg streptozotocin per kg body weight. The duration of diabetes was 6 weeks. A group of 15 age-matched rats, injected only with the buffer and maintained over the same time period, served. as the controls. In en face preparations of the thoracic aorta, IgG-containing dead endothelial cells were identified by an indirect immunoperoxidase method, and endothelial leakage to Evans blue-albumin complexes was quantified by fluorescence microscopy. Diabetic rats, compared to control rats, had significantly higher values for the frequency of endothelial cell death (0.77±0.10% vs 0.38±0.04%;p〈0.005 by two-tailed, unpaired Student'st-test) and the number density of Evans blue-albumin leaky foci (4.33±0.48/mm2 vs 2.99±0.38/mm2;p〈0.05 by two-tailed, unpairedt-test) in the aorta. It is concluded that, similar to the situations in hypertension and nicotine consumption, the observed increase in the frequency of endothelial cell death and macromolecular permeability to large molecules in the aorta in streptozotocin-induced diabetic rats suggest that these changes may contribute to accelerated atherogenesis in diabetes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 27 (1992), S. 5620-5622 
    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 The effects of different electric fields (4.2, 8.3, 12.5, 16.7 and 20.8 Vcm−1) on the sheet resistance, R s, and optical band gap, E obg, of As2Se3 samples (1×105nm) that were photodoped by Ag (5×103nm) have been studied. The R s and E obg of samples subjected to an electric field of 12.5 Vcm−1 decrease linearly to a distance of 5 mm from both electrodes, and then saturate at larger distances. This result suggests that there is a critical value of the electric field which affects photodoping. The dependence of R s and E obg on the distance from the electrodes shows similar profiles for these electrodes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 27 (1992), S. 5635-5639 
    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 InP crystals, grown by the liquid-encapsulated Czochralski method, were prepared by rapid thermal annealing and were investigated by photoluminescence spectroscopy as a function of annealing time. In the photoluminescence spectra of as-grown samples, the 1.414 eV acceptor-bound peak and the 1.378 eV free-to-acceptor peak dominated. A shift toward higher energy was observed at high excitation intensity for the 1.375 eV peak of the donor-to-acceptor emission of InP. The dominant transition centred at the 1.378 eV peak can be ascribed to zinc impurities in the starting material. Changes in the excitation intensity and the sample temperature resulted in the identification of zinc-related free-to-acceptor transitions where the zinc ionization energy was calculated to be 46 meV. Analysis of the temperature-dependent data yield an activation energy of 47 meV.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 28 (1993), S. 3423-3426 
    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 The hydrogenation effects on the defect levels existing in bulk n-GaAs were investigated by deep-level transient spectroscopy and photoluminescence. The three electron traps of the GaAs bulk samples were observed, and their activation energies wereE c — 0.35 eV (E1), 0.56 eV (E2), and 0.81 eV (E3). After hydrogenation at 250 °C for 3 h, the electron trap atE c — 0.35 eV was almost completely passivated and a new trap (EN1) atE c — 0.43 eV was observed. As a result of furnace annealing for 5 min at 300 °C, the EN1 trap disappeared, and the E3 trap passivated by hydrogenation reappeared. In particular, the trap E1 recovered to 90%. The photoluminescence measurements of the hydrogenated samples show that the germanium-related peak was passivated, and the intensity of the dominant bound exciton peak increased remarkably. After a thermal annealing for 15 min at 300 °C, the original intensity of the germanium-related peak was restored.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 485-498 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A calcium phosphate cement, Grossman sealer, and Sargenti N2 were compared under conditions where root canals of monkey incisors were deliberately overfilled and the apical tissue responses were evaluated histologically. The periapical tissues exposed to Sargenti N2 revealed severe irritation at all times through the 6-month experimental period. The reactions to Grossman sealer were milder but persisted throughout the observation period. The calcium-phosphate-cement treated animals showed mild tissue irritation after 1 month, but thereafter the adverse tissue reactions were minimal. New bone formation adjacent to the cement was also observed. These results point to the possibility that calcium phosphate cement might be used in simplified endodontic procedures. The compatibility of calcium phosphate cement with the periapical tissue suggests that the cement may have other applications in dentistry and medicine.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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