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  • 1
    Electronic Resource
    Electronic Resource
    A size of ∼1  au for the radio source Sgr A* at the centre of the Milky Way (2005)
    [s.l.] : Nature Publishing Group
    Nature 438 (2005), S. 62-64 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Although it is widely accepted that most galaxies have supermassive black holes at their centres, concrete proof has proved elusive. Sagittarius A* (Sgr A*), an extremely compact radio source at the centre of our Galaxy, is the best candidate for proof, because it is the closest. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04205
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  • 2
    Electronic Resource
    Electronic Resource
    Reverse-biased performance of a molecular-beam-epitaxial-grown AlGaAs/GaAs high-power optothyristor for pulsed power-switching applications (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5225-5230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reverse-biased performance of a molecular-beam-epitaxy-grown high-power optothyristor has been systematically characterized for pulsed power-switching applications. The device has a P+N-SI-PN+ thyristor-like structure with the bipolar junctions formed by AlGaAs. The semi-insulating (SI) GaAs used is liquid-encapsulated-Czochralski grown, undoped, and 650 μm in thickness. It is found that the reverse-biased optothyristor can be triggered by a light-emitting diode operated at 10−5 W, and miniature semiconductor lasers can trigger the switch with 132 A current using only a 1-mm-diam optical aperture. The reverse switching di/dt and the maximum peak current are reported as a function of blocking voltage. The effects of bipolar junctions on both sides of the SI-GaAs are also reported by comparing the bulk photoconductive current with the optothyristor switched current. It is shown that a laser beam of 0.05 μJ can be used to trigger on and switch about the same current as a 0.3 μJ laser beam, suggesting the possibility of integrating miniature semiconductor lasers and the optothyristors on the same chip to form a portable, compact, high-power solid-state pulser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354262
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular-beam-epitaxial-grown n-GaAs1−xSbx/N-GaAs heterostructures characterized by admittance spectroscopy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7491-7495 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The admittance spectroscopy technique has been applied to characterize deep traps in molecular-beam-epitaxial-grown n-GaAs1−xSbx/N-GaAs heterostructures. A single dominant defect has been identified in each of the three samples containing different Sb content. It was found that the substrate misorientation appears to affect the formation of the dominant defect, resulting in different defects in samples grown under the same conditions. It shows a good agreement when comparing the admittance spectroscopy results with those of the previously reported work of deep-level transient spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353995
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  • 4
    Electronic Resource
    Electronic Resource
    Acute toxicity of ammonia to the early stage-larvae and juveniles of Eriocheir sinensis H. Milne-Edwards, 1853 (Decapoda: Grapsidae) reared in the laboratory (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 28 (1997), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Static-renewal bioassays were performed to evaluate the acute toxicity of ammonia to Eriocheir sinensis (H. Milne-Edwards) at three growing stages, namely zoea-I, zoea-II, and juvenile (0.06 g wet weight per crab). The 24 h LC50 values were 13.3, 20.2, and 109.3 mg (NH3+ NH4+) 1−1 (0.47, 0.71, and 3.10 mg NH3 I−1), the 48 h LC50 values being 6.8, 10.3, and 60.9 mg (NH3+ NH4+) 1−1 (0.24, 0.36, and 1.73 mg NH31−1), while the 72 h LC50 values were 5.7, 7.6, and 45.3 mg (NH3+ NH4+) 1−1 (0.20, 0.27, and 1.29 mg NH3 1−1) for zoea-I, zoea-II, and juveniles, respectively. The 96 h LC50 value for juveniles was 31.6 mg (NH3+ NH4+) 1−1(0.90 mg NH31−1). It was evident that the tolerance to ammonia increased during the same exposure time as the larvae developed to juveniles and decreased with prolonged exposure time. Compared with larvae, juveniles were more sensitive to the fluctuation of ambient ammonia concentrations in the certain range within which partial kills took place. The ‘safe level’ of ammonia based on the 96 h LC50 value and an application factor of 0.1 was 3.16 mg (NH3+NH4+)1−1 (0.09 mg NH3 1−1) for juveniles and those for zoea-I and zoea-II were 0.57 and 0.76 mg (NH3+ NH4+) 1−1 (0.02 and 0.03 mg NH3 1−1) based on 72 h LC50 values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1997.00888.x
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  • 5
    Electronic Resource
    Electronic Resource
    Lethal doses of ammonia on the late-stage larvae of Chinese mitten-handed crab, Eriocheir sinensis (H. Milne-Edwards), (Decapoda: Grapsidae) reared in the laboratory (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 29 (1998), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Four successive life stages (zoea-III, zoea-IV, zoea-V and megalopa) of the Chinese mitten-handed crab, Eriocheir sinensis (H. Milne-Edwards), were exposed to ammonia in a series of short-term bioassays with the static-renewal method at 22°C, pH 8.0 and 25%o salinity. The greatest sensitivity was observed in the zoea-III stage. The 24-h LC50 values for zoea-III, zoea-IV, zoea-V and megalopa were 32.8, 73.1, 84.0 and 90.1 mg L−1 for NH3+ NH4+, and 1.11, 2.36, 2.77 and 3.18 mg L−1 for NH3, respectively. The 72-h LC50 values for zoea-III, zoea-IV and zoea-V were 11.9, 23.6 and 38.2 mg L−1 for NH3+ NH4+, and 0.40, 0.76 and 1.26 mg L−1 for NH3, respectively. The 96-h LC50 values for megalopa were 37.3 mg L−1 for NH3+ NH4+ and 1.31 mg L−1 for NH3. It was found that ammonia tolerance increased with larval development from zoea-III to megalopa, especially from zoea-III to zoea-IV and from zoea-IV to zoea-V. A comparison of safe levels of ammonia among the different life stages indicated that all stages were significantly different with respect to safe levels of ammonia (P 〈 0.05) except zoea-V and megalopa, which had the highest safe levels. In general, both the larvae and juveniles of E. sinensis are less resistant to ammonia than those of other crustacean species studied so far.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1998.00253.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of BCl3 magnetron ion etching on deep levels in GaAs (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5512-5513 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Capacitance versus voltage curves and deep-level transient spectroscopy have been used to investigate the effects of BCl3 magnetron ion etching on the shallow donor concentration and deep-level defects in GaAs. Capacitance versus voltage data reveal that the shallow donor concentration is unaffected by the etching process at power densities ranging from 0.08 to 0.4 W/cm2. Capacitance transient measurements reveal thermal emission of electrons from two deep defect sites with activation energies of 0.25 and 0.74 eV which were unaffected by the etching process. A broad, deep-level transient spectroscopy peak, characterized by an activation energy for thermal emission of electrons of 0.37 eV, was also observed in the etched sample, but not in the unetched sample. Defect depth profiling of the 0.37 eV peak indicates the concentration of this defect to increase with increasing etch power.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351947
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  • 7
    Electronic Resource
    Electronic Resource
    Device geometry and temperature dependence of deep level transient spectroscopy spectra of GaAs metal-semiconductor field-effect transistors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3895-3897 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A resistance deep level transient spectroscopy (DLTS) model is presented which shows how the surface electron traps in GaAs metal-semiconductor field-effect transistors may result in the extensively reported signals attributed to hole trapping at the channel and substrate interface. By considering the detailed electron capture and emission processes of the surface states, the following have been successfully explained for the strong dependence of the surface state DLTS peak height on the device geometry and temperature: (i) the device geometry dependence of DLTS peak height is found to result from the fact that the amount of surface states involved in electron capture and emission in a DLTS study is proportional to the dimension of the ungated region; (ii) the drastic decrease of surface state DLTS peak height with decreased temperature is shown to be a direct result of the strong temperature dependence of the surface leakage current; and (iii) it is shown that the "holelike'' DLTS signals can be used directly to determine the surface electron trap energy level ET.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344995
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  • 8
    Electronic Resource
    Electronic Resource
    Design of solid/liquid–liquid/solid trilayer systems for the measurement of diffusion coefficients in liquid metals (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3002-3005 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method for investigation of diffusion processes in liquid metals with solid/liquid–liquid/solid trilayer systems is described. The design of this kind of trilayers enables diffusion processes with no effects from gravity-induced convection and Maragoni-convection conditions. The Ta/Zn–Sn/Si trilayers were prepared and the interdiffusion of liquid zinc and tin at 500 °C was investigated. The interdiffusion coefficients range from 1.0×10−4 to 2.8×10−4 mm2/s, which are less than previous values measured by capillary reservoir technique under 1 g environment where various kinds of convection exist. It is the removing of disturbances of these kinds of convection that brings about the precise interdiffusion coefficients in liquid metals. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149047
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  • 9
    Electronic Resource
    Electronic Resource
    Preisach analysis of two ferromagnetic perovskites: La0.95Mg0.05MnO3 and La0.5Sr0.5CoO3 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7248-7250 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the major hysteresis loop and of the temperature dependence of the field cooled and zero field cooled moment in applied fields less than the coercive field have been performed on two ferromagnetic perovskites La0.95Mg0.05MnO3 and La0.5Sr0.5CoO3. The data have been analyzed within the framework of a generalized Preisach model which includes thermal fluctuations, critical effects, and a temperature dependent distribution of free energy barriers. The analysis shows that the response functions of the manganese perovskite are dominated by the growth of the anisotropy barriers, while in the cobalt perovskite, thermal fluctuations and barrier growth play a roughly equal role. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355340
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  • 10
    Electronic Resource
    Electronic Resource
    Room-temperature ferromagnetism in zincblende CrSb grown by molecular-beam epitaxy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2776-2778 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of CrSb grown by solid-source molecular-beam epitaxy on GaAs, (Al, Ga)Sb, and GaSb are found to exhibit ferromagnetism. Reflection high-energy electron diffraction and high-resolution cross sectional transmission electron microscopy both indicate that the structure is zincblende. Temperature dependence of remanent magnetization shows that the ferromagnetic transition temperature is beyond 400 K. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1413732
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