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  • 1990-1994  (4)
  • 1980-1984  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Raman scattering of (GaAs)n(GaP)n short-period superlattices prepared by pulsed jet epitaxy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6713-6715 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have carried out the Raman-scattering measurement of (GaAs)n(GaP)n short-period superlattices (n=1–5) prepared by the atomic layer epitaxy technique called pulsed jet epitaxy (PJE). The zone-folding effects on the longitudinal-acoustic (LA) phonon were observed for all the samples. The Raman peak observed for the (GaAs)1(GaP)1 monolayer superlattice has also been tentatively assigned to the scattering from zone-folded LA phonons. If the assignment is correct, this is the first observation of the zone-folded LA phonon in a semiconductor monolayer superlattice. The present results suggest that the growth proceeds atomic layer by atomic layer in PJE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348893
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative study of self-limiting growth of GaAs using different Ga-alkyl compounds: (CH3)3Ga, C2H5(CH3)2Ga, and (C2H5)3Ga (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5660-5664 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied the self-limiting growth of GaAs using three kinds of Ga-alkyl compounds−trimethylgallium (TMGa), ethyldimethylgallium, and triethylgallium−as atomic layer epitaxy (ALE) sources. Perfect self-limiting behavior was found only for TMGa. The self-limiting mechanism could be explained by the surface site selectivity of the metalorganic molecules in the adsorption, desorption, and decomposition processes. We found that the degree of the site selectivity declined as methyl groups attached to a Ga atom were replaced by ethyl groups. We believe that the TMGa molecule is adsorbed without decomposition in the first step, and then fully decomposed into Ga. Three methyl groups of the adsorbed TMGa play an important role in the site selectivity and make the growth self-limited. We studied the evolution of the chemical state of the TMGa-exposed (001) GaAs surface by changing the length of the interruption following a TMGa pulse. There was no change in the surface chemical conditions and in the degree of self-limiting during the H2 purge after TMGa pulse. These results provide a detailed understanding of the surface chemistry and self-limiting growth involved in ALE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346980
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Atomic layer epitaxy of GaP and elucidation for self-limiting mechanism (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 827-829 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic layer epitaxy (ALE) of GaP was performed for the first time in a low-pressure metalorganic vapor phase epitaxial (MOVPE) reactor using trimethylgallium (TMG) and phosphine (PH3) as sources. Growth was self-limiting for the exposure time of each reactant. X-ray photoelectron spectroscopy (XPS) analyses were carried out to identify the adsorbates on the growth surface. There were no methyl groups on the surface Ga and the self-limiting mechanism is due to the selective adsorption of TMG by the surface P atoms. When the substrate was exposed to a sufficient TMG flow after a submonolayer Ga was deposited by triethylgallium (TEG), growth was still self-limiting. This supports the selective adsorption model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102675
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  • 4
    Electronic Resource
    Electronic Resource
    Properties of ventromedial hypothalamic neurons with axons to midbrain central gray (1982)
    Springer
    Experimental brain research 46 (1982), S. 292-300 
    Details
    ISSN: 1432-1106
    Keywords: Ventromedial nucleus ; Hypothalamus ; Antidromic activation ; Central gray ; Midbrain ; Amygdala
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In female rats anesthetized with urethane, 151 neurons in and around the ventromedial nucleus of the hypothalamus were identified by antidromic activation as having axonal projection to the mesencephalic central gray at the midcollicular level. Identified neurons were most numerous in the rostral part and at the borders of the nucleus. Antidromic spike latencies, constant for a given cell to stimulation with fixed intensity at a low repetition rate, had a wide range across cells (1.4–41.5 ms). In 37 cells, gradual increases in stimulus intensity allowed sudden discrete latency decreases as large as 9.8 ms. These may reflect activation of separate axonal branches of terminal arborizations. Eleven among 43 tested cells were antidromically driven from the dorsal longitudinal fasciculus (DLF) at the diencephalic-mesencephalic junction as well as from the central gray. Latencies of DLF responses were always shorter than those from central gray. From this and collision experiments between central gray-evoked and DLF-evoked antidromic spikes, it was concluded that at least one quarter of mesencephalic projections from the ventromedial nucleus descend through DLF. The mean conduction velocity of these axons was 0.8 m/s, indicating that they belong to thin unmyelinated C-group fibers. Thirty percent of the cell population studied received excitatory input from the cortical or medial nucleus of the amygdala. Four cells were identified as having projections both to the central gray and the amygdala. Estrogen treatment of ovariectomized female rats caused no major changes in antidromic latency, absolute refractory period or resting activity of these identified hypothalamic neurons. However, the stimulation threshold for antidromic activation was significantly lower in the estrogen-treated animals. Axons to the central gray from ventromedial hypothalamic neurons provide for hypothalamic bias on brain stem reflex paths, for reproductive and other behaviors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237187
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  • 5
    Electronic Resource
    Electronic Resource
    Estrogen reduces the excitability of the female rat medial amygdala afferents from the medial preoptic area but not those from the lateral septum (1994)
    Springer
    Experimental brain research 101 (1994), S. 1-7 
    Details
    ISSN: 1432-1106
    Keywords: Amygdala ; Estrogen ; Preoptic area ; Septum ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Electrical stimulation of the medial amygdala (AMY) elicited antidromic action potentials in neurons in the preoptic area (POA) and the lateral septum (LS) of 36 urethane-anesthetized ovariectomized female rats, which were either treated with estrogen o not treated. The extracellular potentials from the two sites showed similar characteristics, with the exception of the sensitivity to estrogen: they had latencies between 3 and 35 ms. Thresholds were as low as 100 μA. The mean relative refractory period was 2.2 ms. The peak-to-peak amplitudes of the positive-negative biphasic potential ranged from 1.0 mV to 12.0 mV. Estrogen had site-specific effects on parameters of antidromic activation in the POA. Estrogen-treated rats had a significantly higher threshold (937 vs 664 μA) and a longer refractory period (2.5 vs 2.1 ms) than the ovariectomized rats (P 〈 0.05 for each). The effects were absent in the LS. Selective cutting of the stria terminalis diminished the AMY-induced antidromic responses in the POA and LS. Electrical stimulation of the stria blocked the AMY-induced antidromic potentials by collision. Thus, estrogen-sensitive POA efferents as well as non-estrogen-sensitive LS efferents project to the AMY via the stria terminalis. Reductions in axonal excitability would inhibit neural conduction and transmission. Estrogen may therefore reduce the AMY inputs from the POA, without affecting those from the LS. Such alterations in the neural impulse flow may underlie estrogen-dependent neuroendocrine or behavioral regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243211
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  • 6
    Electronic Resource
    Electronic Resource
    The polypeptide of a human calicivirus (1983)
    Springer
    Archives of virology 78 (1983), S. 1-7 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Viral particles morphologically resembling animals caliciviruses in the faeces of a patient with acute gastroenteritis were purified, radiolabeled with [125I], and analyzed by SDS-PAGE. A single major structural protein with a mol. mass 62,000 daltons was identified by immunoprecipitation technique. The finding is consistent with human calicivirus-like particles associated with gastroenteritis being a member of the family Caliciviridae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01310853
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