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  • 1
    Electronic Resource
    Electronic Resource
    Field effect on thermal emission from the 0.40 eV electron level in InGaP (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 771-774 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results are reported of electric-field dependence on thermal emission of electrons from the 0.40 eV level at various temperatures in InGaP by means of deep-level transient spectroscopy. The data are analyzed according to the Poole–Frankel emission from the potentials which are assumed to be Coulombic, square well, and Gaussian, respectively. The emission rate from this level is strongly field dependent. It is found that the Gaussian potential model is more reasonable to describe the phosphorus-vacancy-induced potential in InGaP than the Coulombic and square-well ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353336
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  • 2
    Electronic Resource
    Electronic Resource
    Destabilization of Glial Fibrillary Acidic Protein mRNA in Astrocytes by Ammonia and Protection by Extracellular ATP (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 63 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The expression of the astrocyte-specific intermediate filament protein, glial fibrillary acidic protein (GFAP), is decreased in hepatic encephalopathy and increased in numerous neurological conditions including brain injury. However, little is known about the molecular mechanisms that regulate GFAP expression. Here it is reported that treatment of cultured astrocytes with ammonium chloride reduces GFAP mRNA by up to 85% without inhibiting total RNA synthesis. The effect of NH4Cl was time and dose dependent. The reduction in GFAP mRNA was detected 3 h after initiation of ammonia treatment with a maximum effect observed at 24 h. Significant decreases in GFAP mRNA were observed at 2, 5, and 10 mM NH4Cl. Concurrent treatment with extracellular ATP prevented the loss of GFAP mRNA, possibly by activation of purinergic receptors. In addition, removal of ammonium chloride restored GFAP mRNA to normal levels. Nuclear runoff experiments indicated that NH4Cl did not inhibit GFAP mRNA transcription. Studies using α-amanitin, an inhibitor of RNA polymerase II, showed that NH4Cl decreased the stability of GFAP mRNA by ∼50%. This destabilization of GFAP mRNA may be an important factor in the pathogenesis of hepatic encephalopathy. Because increased GFAP is an important component of reactive gliosis, understanding the mechanisms that destabilize GFAP mRNA may facilitate strategies to minimize the gliosis associated with brain injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.63062021.x
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  • 3
    Electronic Resource
    Electronic Resource
    Synergistic Activation of DNA Synthesis in Astrocytes by Fibroblast Growth Factors and Extracellular ATP (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 63 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of extracellular ATP and polypeptide growth factors on DNA synthesis in primary cultures of rat astrocytes have been examined. It was found that ATP acts synergistically with either acidic or basic fibroblast growth factor to stimulate DNA synthesis. The specificity of this effect was demonstrated by the inability of ATP to potentiate DNA synthesis induced by platelet-derived growth factor or epidermal growth factor. ATP appears to act via P2 purinergic receptors, because (a) it was more effective than adenosine and (b) the synergistic effect was observed with the hydrolysis-resistant P2 agonists, ADPβS and ATPγS. The evidence suggests that extracellular ATP may be an important factor in regulating the extent of gliosis and, as such, may be involved in mechanisms of neural injury and repair.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.63020490.x
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  • 4
    Electronic Resource
    Electronic Resource
    Deep center scattering potential in InGaP (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7410-7414 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mobility limited by the scattering of a phosphorous vacancy-induced deep center in In0.5Ga0.5P alloy grown by liquid-phase epitaxy on a (100) GaAs substrate has been investigated by means of Hall mobility and deep-level transient spectroscopy measurements. Two kinds of scattering potentials, Gaussian well type and square-well type, were considered. It was found that the scattering potential can be better described by the Gaussian-type potential than the square-well one. The mobility limited by deep center scattering has been fully calculated and analyzed. As a result, the mobility is characterized by a temperature dependence of T−1/2 in the temperature range from 77 to 400 K. The point defect scattering severely reduces the total mobility as its concentration increases. In addition, the scattering case when there is an electron trapped in the Gaussian potential well was also quantitatively investigated. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358524
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  • 5
    Electronic Resource
    Electronic Resource
    Linewidth of the infrared absorption spectra due to bound-to-continuum transition in GaAs/AlxGa1−xAs multiple quantum well structures (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1131-1133 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed an extremely narrow absorption spectrum due to bound-to-continuum transition in GaAs/AlxGa1−xAs multiple quantum wells (MQWs). Its linewidth is only about one tenth of the values reported previously. Our calculation indicates that the broadening of the excited state in the continuum has little contribution to the absorption linewidth. We have grown a sample whose MQW region contains two kinds of wells with a minor thickness inhomogeneity. Its resultant absorption linewidth is six times as large as that of homogeneous well sample, which is in good agreement with our theoretical analysis. Thus we can suggest that the wider absorption spectra reported by many authors may be due to the well width inhomogeneity. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122106
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  • 6
    Electronic Resource
    Electronic Resource
    Structural properties of GaN films grown on sapphire by molecular beam epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1141-1143 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural characteristics of GaN films grown on sapphire substrates by molecular beam epitaxy have been investigated using high-resolution synchrotron x-ray diffraction and electron microscopy. We find remarkable correspondence between the in-plane structural order (coherence length and mosaic spread) and the electrical and optical properties. Contrary to common belief, our observations show unequivocally that the out-of-plane structural features, which are considerably better developed than the in-plane counterparts, cannot be used for determining the material quality with respect to their optical and electrical activity. In particular, the (00l) mosaic spread is not a good indicator of film quality. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115739
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  • 7
    Electronic Resource
    Electronic Resource
    Radiation temperatures of soda-lime glass in its shock-compressed liquid state (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1711-1716 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A radiation pyrometer in conjunction with a two-stage light gas gun has been used to measure shock temperatures of soda-lime glass in the pressure range 54–109 GPa. This pyrometer consists of two parts, i.e., an optical multichannel analyzer which measures the radiation spectrum over the visible range (∼450 nm window) and a four-channel photomultiplier tube system which records the time-varying behavior of shock temperatures. The measured radiation spectra are compared with the Planck function to estimate the shock temperatures and emissivities. Obtained spectra are well fit by the Planck function with moderate emissivities, indicating that relatively homogeneous thermal radiation is the main component of radiation. Obtained shock temperatures range from 2800 (100) to 5700 (300) K and they seem to represent shock temperatures of liquefied soda-lime glass (melt). The Hugoniot is well described by a linear relation, us=0.14(21)+1.92(5)up km/s. It is deduced that the radiation from liquids under shock compression, in contrast to the radiation from solids under shock compression, is more thermal and fits the Planck function well, even at lower temperatures. This is because the radiation spectrum of solids under compression often shows nonthermal radiation due to heterogeneous deformation, while the radiation spectrum of liquids under compression could not have such a nonthermal component. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366889
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  • 8
    Electronic Resource
    Electronic Resource
    Transient behavior of a-Si(C):H bulk barrier color detectors (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3906-3910 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photocurrent transient of a-Si(C):H n-i-p-i-n/p-i-n-i-p color detectors under pulse illumination at different wavelengths has been investigated. In contrast to amorphous silicon Schottky diodes and p-i-n/n-i-p structures, the photocurrent decay after the end of the steady state illumination is barely influenced by the applied bias voltage. Moreover, a reversal of the photocurrent direction can be observed under certain bias when the light is being switched on. It is suggested that these properties of n-i-p-i-n/p-i-n-i-p structures are mainly attributed to the accumulation and trapping of the photogenerated carriers near the central barrier. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367146
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of the conduction-band offset of a single AlGaAs barrier layer using deep level transient spectroscopy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2813-2814 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The tunneling from an AlGaAs confined thin layer to a GaAs layer in the GaAs/Al0.33Ga0.67As/GaAs structure during the trapped electron emission from deep level in the AlGaAs to its conduction band has been observed by deep level transient spectroscopy. With the aid of the tunneling effect, the conduction-band offset ΔEc was determined to be 0.260 eV, corresponding to 63% of ΔEg. A calculation was also carried out based on this tunneling model by using the experimental value of ΔEc=E2−E1=0.260 eV, and good agreement between the experimental and calculated curves is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109218
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of the sub-band energy in the V-shaped potential well of δ -doped GaAs by deep level transient spectroscopy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2425-2427 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using deep level transient spectroscopy (DLTS) the conduction-subband energy levels in a V-shaped potential well induced by Si-δ doping in GaAs were determined. Self-consistent calculation gives four subbands in the well below the Fermi level. Experimentally, two DLTS peaks due to electron emission from these subbands were observed. Another two subbands with low electron concentration are believed to be merged into the adjacent DLTS peak. A good agreement between self-consistent calculation and experiment was obtained. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112695
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