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  • 1995-1999  (4)
  • 1990-1994
  • 1950-1954
  • 1998  (4)
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  • 1995-1999  (4)
  • 1990-1994
  • 1950-1954
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  • 1
    Electronic Resource
    Electronic Resource
    Optical-field calculations for lossy multiple-layer AlxGa1−xN/InxGa1−xN laser diodes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1196-1203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical-field profiles in wide-band-gap AlxGa1−xN/InxGa1−xN multiple-quantum well (MQW) separate-confinement heterostructure (SCH) laser diodes (LDs) were calculated using a 2×2 transfer-matrix approach that accommodates complex refractive indices. The refractive indices of AlxGa1−xN and InxGa1−xN were approximated by shifting the refractive index of GaN according to the band-gap energy of the solid solution. Current LDs were analyzed and show reasonable optical confinement. Optimization of the SCH waveguide for a three MQW active region was performed by varying the waveguide and cladding layer thicknesses. For 0.8μm thick Al0.10Ga0.90N cladding layers, waveguides on sapphire and SiC substrates had a maximum confinement factor of ∼3.3%. Layers outside of the waveguide strongly affected the optical field for thin (∼0.4 μm) cladding layer thicknesses and resulted in resonant coupling of the light out of the waveguide. Sapphire substrates were found to enhance light confinement, while SiC substrates were found to reduce optical confinement as the cladding layer thickness is reduced. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368185
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Medullomyoblastoma: a histological, immunohistochemical, ultrastructural and molecular genetic study (1998)
    Springer
    Acta neuropathologica 95 (1998), S. 205-212 
    Details
    ISSN: 1432-0533
    Keywords: Key words Medullomyoblastoma ; Medulloblastoma ; c-myc ; c-erb-B2 ; Allelic loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Medullomyoblastoma is a rare variant of medulloblastoma containing myoblastic elements. A 9-year-old boy developed a cerebellar syndrome and signs of increased intracranial pressure, the cause of which was a tumor of the cerebellar vermis measuring 7 × 4.5 × 4.5 cm. Morphologically the tumor largely consisted of a medulloblastoma component but displayed glial, myoblastic and ganglionic differentiation on light microscopic, immunohistochemical and ultrastructural examination. The non-enhancing rim of the tumor on magnetic resonance imaging showed extensive ganglionic differentiation. The tumor did not express bcl-2, c-myc, or c-erb-B2 oncoproteins and was negative for the p53 gene product. On molecular genetic studies, the tumor did not show allelic loss on chromosome loci, frequently altered in medulloblastomas, such as 17p, 1q and 9q.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050788
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Localization of fibroblast growth factor 2 (FGF-2) protein and the receptors FGFR 1–4 in normal human seminiferous epithelium (1998)
    Springer
    Histochemistry and cell biology 110 (1998), S. 57-62 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Fibroblast growth factor 2 (FGF-2), which occurs in various isoforms both species and tissue specifically, regulates cell proliferation and differentiation via a dual receptor system consisting of heparan sulphate proteoglycans and receptor tyrosine kinases (FGFRs). This study demonstrates for the first time the distribution pattern of FGF-2 and the receptors FGFR 1–4 in the normal seminiferous epithelium of adult men. In western blot analyses, the polyclonal antibody, anti-FGF-2, shows two immunoreactive bands at 18 and 24 kDa. On paraffin sections, positive immunoreaction occurs within the cytoplasm of spermatogonia. The distribution pattern of the polyclonal anti-FGFR 1–4 antibodies is as follows: anti-FGFR-1 (one 68-kDa band) stains nuclei and cytoplasm of spermatogonia; anti-FGFR-3 (five bands at 68, 78, 105, 125 and 145 kDa) stains the nuclei of all germ cells except those of elongated spermatids; and anti-FGFR-4 (one 48-kDa band) stains the cytoplasm of primary pachytene spermatocytes. We were unable to demonstrate FGFR-2 immunoreactivity either in western blot analysis or on paraffin sections. This distribution pattern suggests that FGF-2 in spermatogonia is involved in the autocrine and paracrine regulation of the proliferation and differentiation of spermatogonia and spermatocytes via the receptors FGFR-1, FGFR-3 and FGFR-4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180050265
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  • 4
    Electronic Resource
    Electronic Resource
    Decreasing diffusion limitation on exercise in lower-graded interstitial lung disease (1998)
    Springer
    Pflügers Archiv 435 (1998), S. 762-766 
    Details
    ISSN: 1432-2013
    Keywords: Key words Isotopic analysis ; Overall fractionation factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study we investigated the contribution of diffusion limitation to the exercise-induced hypoxaemia in interstitial lung disease (ILD). We applied isotopic analysis to the composition of the stable isotopic oxygen molecules 16O2 and 16O18O in expiratory gas mixtures obtained from six ILD patients and six healthy subjects at rest and during ergometer work (60 W). The changes in the 16O18O/16O2 ratios were interpreted by using the overall fractionation factor of respiration (α O) which would be increased towards 1.03 on increasing diffusion limitation. In addition, the O2 partial pressures of alveolar gas and arterial blood (P AO2, P aO2) were determined. In the patients, α O was significantly reduced from 1.0066 ± 0.0004 (mean ± SD) at rest to 1.0035 ± 0.0004 during exercise and in the healthy subjects from 1.0072 ± 0.0008 to 1.0044 ± 0.0004. Furthermore, the exercise-induced reduction of P aO2 (from 77 to 69 mmHg) was due to a drop of alveolar PO2 found in each patient, whereas in each healthy subject P aO2 was increased on exercise. On the basis of a resistance model we conclude that the patients’ data were inconsistent with increasing diffusion limitation but showed an increasing impairment of O2 transport by ventilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050581
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    Paper (German National Licenses)
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