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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2289-2291 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A double-heterojunction angled stripe AlGaAs device consisting of an index-guided ridge waveguide with gain-guided facet regions has produced cw output powers of 20 mW with less than 1% spectral modulation from a 300-μm-long diode. These properties enable these devices to have important use in high-sensitivity fiber optic gyroscopes and as broadband traveling-wave optical amplifiers.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1501-1503 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The performance of a series of InxGa1−xAs/AlGaAs (x=0.20 and 0.25) strained single quantum well (SSQW) lasers with lasing wavelengths in the range 930≤λ≤1000 nm is discussed. Less-strained devices, with x=0.20 and QW thickness 7 nm (λ∼930 nm), perform comparably with GaAs QW lasers. Longer wavelength (λ〉950 nm), more highly strained lasers exhibit poorer performance. Our results suggest that interfacial recombination limits the performance at the longer wavelength structures.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2371-2373 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Continuous wave (cw), high-power operation of a strained In0.2Ga0.8As/ AlGaAs quantum well laser, grown by atmospheric pressure organometallic vapor phase epitaxy, is reported. The laser active region consists of a single 70 A(ring) In0.2Ga0.8As/Al0.2Ga0.8As quantum well, with optical confinement provided by a graded index separate confinement heterostructure. The threshold current density and differential quantum efficiency of a 90 μm×600 μm stripe with uncoated facets are ∼200 A/cm2 and 46%, respectively. Lasing wavelength is ∼930 nm, and the cw single ended power versus current characteristic is linear up to 250 mW (1 A current). In the short-cavity (〈300 μm) regime, these devices have high thresholds and have been observed to lase at shorter wavelength, presumably due to a saturation of gain at the lowest energy transition. The characteristic temperature is 150 K and decreases somewhat with cavity length. This suggests that some nonradiative process, most likely Auger recombination, contributes significantly to quantum well gain saturation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3340-3343 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A strained quantum well laser with a front-end power conversion efficiency exceeding 33% under continuous-wave operation is demonstrated. The laser structure, grown by atmospheric pressure organometallic vapor-phase epitaxy, consists of a 70-A(ring) In0.2Ga0.8As quantum well active region with graded index separate confinement heterostructure. Lasing wavelength is 930 nm, and the front-end differential quantum efficiency is 58% for broad-area oxide stripe lasers with a high-reflection coating on the rear facet. Front-end, continuous power outputs greater than 1 W are available. Although these strained quantum well lasers have threshold currents as low as lattice-matched GaAs quantum well lasers, their internal quantum efficiencies appear to be reduced, thus limiting the maximum attainable conversion efficiency.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 318-320 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By adjusting the carrier confining structure and the optical confining structure of strained InGaAs/AlGaAs single quantum well (QW) lasers, an improvement in performance has been obtained. First, the influence of optical confinement was examined by comparing two graded-index confining structures. For InxGa1−xAs QWs with either x=0.20 or x=0.25, lasers with greater optical confinement factor had improved performance, with both lower threshold (180 A/cm2 for x=0.20) and higher characteristic temperature (250 K for x=0.20), despite their reduced carrier confining potentials. Second, experiments on graded-composition quantum wells show that thin step-grading layers result in improved performance. In this structure, where the QW has x=0.35, and the step layers have x=0.15, the optimum step thickness is 30–40 A(ring). Thicker step layers appear to create too much strain, degrading the laser operation. These results indicate that step grading of strained QWs produces active region interfaces with lower defect density, and that step grading is especially useful in improving the performance of long-wavelength, highly strained InGaAs/AlGaAs QW lasers.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Lesions ; Learning ; Memory ; Lateralization ; Chick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three distinct nuclei of the chick forebrain — the intermediate medial hyperstriatum ventrale (IMHV), lobus parolfactorius (LPO), and paleostriatum augmentatum (PA) — show metabolic, morphological, and neurophysiological changes following training on a passive avoidance task, suggesting that these and other areas of the chick forebrain participate in memory formation for this task. Considerable evidence exists for lateralization of memory processes in the chick. Several experiments examined the effects of lesions in the IMHV on the ability of chicks to learn and retain the avoidance task. Pre-training bilateral lesions in the IMHV produced an impairment in avoidance responding tested three hours after training. Pre-training unilateral lesions in the left but not the right IMHV resulted in a similar impairment. However, bilateral IMHV ablations, given either 1 or 6 h post-training, did not impair retention. IMHV lesions did not impair retention of a simple escape learning task. These results are consistent with other studies that have examined the effects of bilateral IMHV lesions on acquisition of passive avoidance and extend these findings by demonstrating lateralization of acquisition involving the left IMHV. The results also suggest that, as early as one hour post-training, the IMHV is not necessary to retain the memory and indicate that other forebrain structures, possibly the LPO or PA, may maintain the memory trace following training. Hypotheses to account for these results and indications of future research are discussed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2072
    Keywords: Opiates ; Naloxone ; Sodium preference ; Saline consumption ; Thirst ; Sex ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of naloxone on fluid consumption by water-deprived rats trained to choose between a saline solution and water in a 15-min drinking test were examined. Rats of each sex were allocated to three groups and given access to 0.125% NaCl, 0.6% NaCl, and 1.7% NaCl, respectively, as the alternative to water. Under control conditions they drank substantially more of the hypotonic salt solutions than water, but drank slightly more water than hypertonic salt solution. Naloxone generally reduced fluid consumption, dose-dependently (0.01–10 mg/kg). In the cases of the two hypotonic solutions, the suppressant effect of naloxone was limited to saline solution. The usually low levels of water consumption were unaffected. In the case of the hypertonic solution, naloxone suppressed salt and water intakes by equivalent amounts. The effects of naloxone in the tests with the two higher salt concentrations depended upon sex. There was one example of a significant naloxone-induced reduction in saline preference (females; 0.125% NaCl v H2O). In other instances, saline preferences were not significantly modified. The results are briefly discussed in relation to current suggestions that naloxone may affect fluid consumption in ways which are taste-dependent (e.g., taste sensitivity, palatability, reward). An alternative view is also considered, that the effects of naloxone may be taste-independent, at least in the particular case of drinking in a two-choice test with saline and water.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2072
    Keywords: CGS 8216 ; DMCM ; FG 7142 ; Food intake ; Midazolam ; Palatability ; Ro15-1788 ; Satiety ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Non-deprived rats were familiarised with a highly palatable diet until baseline consumption in a 60-min daily access period had stabilised. The benzodiazepine receptor agonist midazolam (1.25–10.0 mg/kg, IP) produced a large, dose-related increase in food consumption during the first 30 min of access. It also produced significant, short-term hyperphagia in animals which had been partially pre-satiated on the diet before drug administration, an effect which was reversible by the benzodiazepine receptor antagonist Ro15-1788. Administered alone, Ro15-1788 (1.25–10.0 mg/kg, IP) had no intrinsic activity in the food consumption test. In contrast, CGS 8216 (2.5–40.0 mg/kg, IP) produced a marked dose-related suppression of food intake. This anorectic effect was shared by two benzodiazepine receptor inverse agonists, FG 7142 and DMCM, which also produced dose-dependent reductions in consumption. The effects on feeding produced by FG 7142 (20 mg/kg, IP) and DMCM (1.25 mg/kg, IP) were reversed by either Ro15-1788 (2.5 and 5.0 mg/kg) or midazolam (5.0 and 10.0 mg/kg). A matched anorectic effect produced by CGS 8216 (40 mg/kg) was not, however, reversed by either Ro15-1788 or midazolam. This suggests that at a high dose CGS 8216 may act by a mechanism different from that of the two inverse agonists. The feeding test described in the report proved sensitive to both hyperphagic and anorectic effects of drugs active at benzodiazepine receptors, pointing to a possible bi-directional control of palatable food consumption.
    Type of Medium: Electronic Resource
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