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  • 1
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2892-2894 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A novel structure, in which the potential profile of the coupled quantum well system is slightly inclined, is proposed for lowering the electric field required to transform the coupled system to a set of uncoupled single quantum wells. Numerical calculations of absorption spectra of graded coupled quantum wells under an electric field and room-temperature photocurrent spectra of fabricated p-i-n diode samples confirm the above enhanced effect.
    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. 2211-2215 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A mobility profiling technique using a field-effect transistor has been successfully applied to characterize the growth interruption interfaces of organometallic vapor-phase epitaxial Si-doped n-GaAs layers. The interface was formed by interrupting the supply of TMGa and SiH4 for certain lengths of time under a pressure of flowing AsH3. The 30-s interruption interface showed a decrease in the carrier concentration and an increase in the mobility, as obtained from the gate capacitance-voltage and transconductance-voltage characteristics. A quantitative analysis led us to a conclusion that the interface in question is not compensated by acceptor impurities or defects, in contrast with an easy conclusion usually deduced only from the carrier concentration profile, but has an effective reduction of Si doping level. A secondary-ion mass spectroscopic (SIMS) depth analysis of Si and C atoms supported the above-mentioned conclusion. The 60-s interruption, however, showed an extremely low drain current, which was caused by overcompensation of Si by C pileup at the interface, as confirmed from the SIMS depth profile. Thus, it was found that electrical compensation of the interface rapidly proceeds during 30–60-s interruption. The mobility profiling, therefore, provides a sensitive and powerful tool for growth interruption analysis.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1620-1622 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We propose a new distributed feedback (DFB) laser structure in which almost pure gain coupling can be embodied in principle, without sacrificing low threshold operation. An analysis of coupling coefficients has revealed the condition for canceling index-coupling component. Utilizing organometallic vapor phase epitaxy, we have fabricated GaAlAs/GaAs ridge waveguide distributed feedback lasers having this structure. Excellent single longitudinal mode oscillation independent of facet reflection has been obtained along with low threshold current. The single-mode spectrum has exhibited distinctive characters of purely gain-coupled DFB lasers.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2674-2676 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A tensile-strained five-step asymmetric coupled quantum well (FACQW) structure is proposed for large field-induced refractive index change without polarization dependence and redshift of the absorption edge. A strong exciton absorption peak is caused by electron-hole transitions between symmetric wave functions and antisymmetric wave functions with a small applied electric field. The field-induced refractive index change of strained the FACQW is larger by one order of magnitude compared to that of a rectangular quantum well and the difference in the refractive index change of TE and TM modes is under 2% when the operation wavelength is not at the absorption edge. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 37-39 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We describe optical short pulse generation in novel gain-coupled distributed feedback (GC-DFB) semiconductor lasers by using a simple electrically pumped gain switching method. An optical pulse as short as 16 ps has been obtained from a 130 ps current pulse. The most exciting result is that the lasers keep single longitudinal mode oscillation with very low wavelength chirping (∼0.12 nm) during the gain switching operation. From the optical pulse width and the amount of the wavelength chirping, we have estimated the α parameter of the GC-DFB laser to be less than 1.6.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 117-118 (Jan. 1993), p. 417-422 
    ISSN: 1662-9752
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0533
    Schlagwort(e): Mitochondrial myopathy ; Cytochrome c oxidase ; Mosaicism of mitochondria ; Electron microscopic histochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Electron microscopic histochemistry was applied to the study of cytochrome c oxidase activity in each mitochondrion of biopsied muscles from four patients with mitochondrial myopathy [one case of fatal infantile mitochondrial myopathy, one case of myoclonus epilepsy associated with ragged-red fibers (MERRF), and two cases of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS)]. In the patient with fatal infantile mitochondrial myopathy, intercellular heterogeneity of mitochondria was recognized. In the three patients with either MERRF or MELAS, cytochrome c oxidase activity was segmentally changed from positive to negative within single muscle fibers. In the two patients with MELAS, small groups of positive-stained mitochondria were located among negative-stained mitochondria in the negative segment of a few muscle fibers. These findings revealed that there were heterogeneous populations of normal and abnormal mitochondria intracellularly or intercellularly within the muscles of these patients.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 85 (1993), S. 370-377 
    ISSN: 1432-0533
    Schlagwort(e): Mitochondrial myopathy ; Cytochrome c oxidase deficiency ; Immunoelectron microscopy ; In situ hybridization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The levels of mitochondrial electron transport system proteins cytochrome c oxidase (COX) and complex III were measured in muscle fibers of patients with mitochondrial encephalomyopathy using quantitative immunoelectron microscopy. In a patient with Leigh's encephalopathy, immunoreactive COX protein was decreased to 20% of the normal mean value in all muscle fibers examined, while the amount of complex III was within the normal range. In a patient with fatal infantile COX deficiency, the level of COX protein was found to be decreased to 27–40% of the normal value in all muscle fibers examined. In patients with mitochondrial myopathy, encephalopathy, lactic acidosis associated with stroke-like episodes (MELAS) and chronic progressive external ophthalmoplegia (CPEO), COX protein levels were decreased to 20% of normal in muscle fibers lacking COX activity. In normal fibers, however, COX protein levels were also normal. The amount of complex III protein was normal in COX-deficient muscle fibers. In two patients, in situ hybridization was performed for detection of mitochondrial mRNA. Mitochondrial mRNAs were found to be abundant in muscle fibers with decreased COX protein, suggesting a defect at the mitochondrial protein-synthesis level in a COX-deficient muscle fiber.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 149 (1990), S. 344-345 
    ISSN: 1432-1076
    Schlagwort(e): Glycogen storage disease Ib ; Secondary amyloidosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We observed the development of generalized amyloidosis in a girl with glycogen storage disease type Ib (GSD-Ib) who showed neutropenia, neutrophil dysfunction and recurrent infections. Renal and thyroid biopsies showed secondary amyloidosis, characterized by the presence of potassium permanganate sensitive Dylon positive deposits in glomeruli, renal vessels and thyroid interstitium. Immunohistochemistry showed that the deposits were composed of amyloid A (AA) protein. Possibly neutrophil abnormalities are involved in the pathogenesis of amyloidosis.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 151 (1992), S. 154-159 
    ISSN: 1432-1076
    Schlagwort(e): Medium-chain acyl-CoA dehydrogenase deficiency ; Sudden infant death ; Reye syndrome ; Mass screening ; DNA diagnosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an autosomal recessive disorder which is known to cause Reye-like syndrome in children and sudden infant death. A point mutation of lysine329-to-glutamic acid329 substitution in the MCAD gene was recently identified as the most common mutation in patients with MCAD deficiency. This mutation is responsible for about 90% of mutant MCAD alleles in Caucasians. Patients with this type of mutation have a variety of symptoms, indicating that the clinical heterogeneity of MCAD deficiency may not be caused entirely by genetic heterogeneity. Screening for the mutation among newborns in England, Australia, and United States of America indicates the prevalence of carriers to be 1 in 40–107, suggesting the high incidence of the mutation. Since presymptomatic diagnosis and appropriate dietary management are important in MCAD deficiency to prevent life-threatening complications, the relatively high incidence of this disorder may warrant population screening. The most common MCAD mutation can now be detected by DNA diagnostic methods using Guthrie cards. This makes it possible to screen a population efficiently for this potentially fatal disorder.
    Materialart: Digitale Medien
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