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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 809-812 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In high-power AlGaAs window structure lasers with a window grown on facets (WGF) structure, dependence of window effects on Al content of the window layer is examined. When the Al content of the window layer is more than that of the cladding layer, the window effects are found. But, in other cases, the window effects do not occur. A calculation of a carrier leakage from the active layer to the window layer is performed. From the result, we deduce that the reduction of the window effects is caused by the carrier leakage. In the WGF laser with the confirmed window effects, a maximum output power of 350 mW is achieved and highly reliable operation under 100 mW at 50 °C beyond 10000 h is attained.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4946-4949 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We studied nonradiative recombination centers in undoped (AlxGa1−x)0.5In0.5Pgrown by metalorganic vapor phase epitaxy using transient capacitance spectroscopy. We found three deep energy levels, including a mid-gap level. We drew an equation to get a capture cross section for minority carriers, and obtained it using isothermal capacitance transient spectroscopy measurement. The mid-gap level had an electron capture cross section of 2 × 10−10 cm2 and a hole capture cross section of 1 × 10−15 cm2. The time constant of nonradiative recombination through the mid-gap level was found to be comparable to that of radiative recombination. We concluded that the mid-gap level is an effective nonradiative recombination center that reduces photoluminescence intensity.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3629-3630 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using time-resolved photoluminescence, we examined the carrier-recombination process in strained AlGaInP/GaInP double heterostructures grown by metal-organic vapor phase epitaxy. We found that interfacial recombination dominates the process at room temperature, and that the interfacial recombination is enhanced by tensile strain and reduced by compressive strain.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1736-1738 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We fabricated a GaInP/AlGaInP visible laser with a real-index guide structure by one-step metalorganic vapor phase epitaxy using simultaneous impurity doping. We achieved an effective self-aligned current-confinement structure in the AlGaInP cladding layer and a threshold current of only 18 mA. The laser had stable transverse-mode oscillation with a beam astigmatism less than 1 μm.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 38 (1982), S. 501-502 
    ISSN: 1420-9071
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Immunopotentiators such as BCG, levamisole, PS-K and OK-432 prevent carbon tetrachloride (CCl4) hepatotoxicity, and in spite of exposure to CCl4 the liver tissue levels of thiobarbituric acid (TBA) reactive substances were not increased in rats pretreated with such immunopotentiators.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 38 (1982), S. 312-313 
    ISSN: 1420-9071
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Feeding under conditions of reduced oxygen supply prompted an increase in serum, arterial and brain tissue levels of thiobarbituric acid (TBA)-reacting substances. These observations indicated the possibility that hypoxia might be one of the factors predisposing to the accumulation of lipid peroxide.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0428
    Schlagwort(e): Islet amyloid polypeptide ; amylin ; diabetes mellitus ; fasting concentration ; oral glucose tolerance test
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Fasting plasma islet amyloid polypeptide concentrations and their responses to an oral glucose load were determined in non-diabetic control subjects and patients with abnormal glucose tolerance in relation to the responses of insulin or C-peptide. Plasma islet amyloid polypeptide was measured by radioimmunoassay. In the non-diabetic control subjects, fasting plasma islet amyloid polypeptide was 6.4±0.5 fmol/ml (mean ± SEM) and was about 1/7 less in molar basis than in insulin. The fasting islet amyloid polypeptide level rose in obese patients and fell in patients with Type 1 (insulin-dependent) diabetes mellitus. In non-obese patients with impaired glucose tolerance and Type 2 (non-insulin-dependent) diabetic patients without insulin therapy, the level was equal to that of the control subjects, but a low concentration of islet amyloid polypeptide relative to insulin or C-peptide was observed in the non-obese Type 2 diabetic group. The patterns of plasma islet amyloid polypeptide responses after oral glucose were similar to those of insulin or C-peptide. However, compared to non-obese patients, a hyper-response of islet amyloid polypeptide relative to C-peptide was noted in obese patients who had a hyper-response of insulin relative to C-peptide. This study suggests that basal hypo-secretion of islet amyloid polypeptide relative to insulin exists in non-obese Type 2 diabetes and that circulating islet amyloid polypeptide may act physiologically with insulin to modulate the glucose metabolism.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-0533
    Schlagwort(e): Acute porphyria ; Porphyric neuropathy ; Axonal degeneration ; Uroporhyrinogen I synthetase ; Ferrochelatase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary An autopsy case of a 37-year-old woman with acute porphyria is reported. The patient began to complain of severe menstrual pains, and later developed serious peripheral neuropathy and various autonomic nervous symptoms. The autopsy revealed a marked loss and degeneration of axons and myelin sheaths in the peripheral nervous system (PNS), and prominent central chromatolysis of the spinal anterior horn cells. The predominant process of the peripheral neuropathy appeared to be axonal degeneration. Biochemical analysis showed a marked increase of delta-aminolevulinic acid (ALA), porphobilinogen, uroporphyrin, and coproporphyrin in the urine, and an increase of coproporphyrin and protoporphyrin in the stools and blood. In the analysis of the enzymatic activities of the liver and bone narrow, the activity of ALA synthetase (ALA-S) was markedly increased, and the activities of both uroporphyrinogen I synthetase (URO-S) and ferrochelatase were decreased. It was characteristic in this case that the enzymatic abnormalities found in both acute intermittent porphyria (AIP) and variegate porphyria (VP) coexisted. Biochemical analysis of the sciatic nerve showed an increase of ALA-S activity and a decrease of both URO-S and ALA dehydrase activities. This was the first report that indicated the presence of abnormal activities of the heme biosynthetic enzymes in the peripheral nerves of porphyric patients. The possibility was discussed that these enzymatic abnormalities of the heme biosynthesis in the peripheral nerve itself might be strongly related to the pathogenesis of the porphyric neuropathy.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-0738
    Schlagwort(e): Lead poisoning ; Erythrocytes ; δ-Aminolevulinic acid dehydratase(ALAD) ; Rat ; Porphyrins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The well known fact that the activity of δ-aminolevulinic acid dehydratase (ALAD: EC 4.2.1.24) is reduced in red cells of animals with lead poisoning was found to be upset, by using a modified method of Gibson's original procedure, for determination of activated ALAD activity. The modified method involves addition of 0.2 mM Zn2+ and then preheating the enzyme solution at 60° C for 5 min before following Gibson's original procedure. With this methodological modification, the ALAD activity of erythrocytes of rats poisoned with lead was found increased. Furthermore, the enzyme was purified from the peripheral blood of lead-poisoned rats. ALAD protein in peripheral blood was also determined by single radial immuno diffusion using rabbit anti-serum raised against rat liver ALAD. As the result, the ALAD activity obtained from the modified method was found to be directly proportional to the absolute amount of enzyme proteins determined both by chemically and immunochemically. The modified method for measuring true ALAD content in blood cells in lead poisoning is more reliable than previous ones.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Histochemistry and cell biology 94 (1990), S. 257-262 
    ISSN: 1432-119X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary A new method has been developed for the precise identification of human bone marrow colony forming unit erythroid (CFU-E) and burst forming unit erythroid (BFU-E) colonies, and for determination of the hemoglobin contents using microcytofluorometry. The method relies on a photochemical reaction in which intracellular hemoglobin is converted into fluorescent porphyrin under violet light (λ=405 nm) in the presence of an SH-donor (mercaptoethylamine hydrochloride). The CFU-E and BFU-E colonies showed red fluorescence with two spectrum peaks at 600 and 650 nm when illuminated by violet light. These two peaks are consistent with those of porphyrin fluorescence. The porphyrin fluorescence was not inducible in colony forming unit granulocyte-macrophage (CFU-GM) colonies, while 20% of the CFU-GM colonies were false positive with respect to the conventional benzidine reaction. The photochemically inducible fluorescence began to appear in BFU-E colonies on the 4th day of culture, while the same colonies started to be positive for the benzidine reaction on the 9th day. Therefore, the photochemical reaction was more specific and sensitive than the benzidine reaction for the identification of CFU-E and BFU-E colonies. In addition, this method enabled us to measure the hemoglobin level in the cells forming the colonies because the intensity of the fluorescence was proportional to the amount of hemoglobin when the photochemical reaction was carried out for 50 min. As a result of qualitative and quantitative analysis of CFU-E colonies by this method, it was possible to detect the hemoglobin levels in the colonies from 1 of 4 cases of untreated acute nonlymphocytic leukemia and from 2 of 4 cases of myelodysplastic syndrome in which the hemoglobin levels were too low to be detected by the benzidine reaction. These cases, where the CFU-E colonies showed very low levels of hemoglobin, were associated with poor prognosis. Thus, our method is useful for identifying CFU-E colonies, determining their hemoglobin synthesis, and as a cue to predict the clinical course of the patients.
    Materialart: Digitale Medien
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