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  • Articles: DFG German National Licenses  (10)
  • 1995-1999  (10)
  • 1999  (3)
  • 1998  (4)
  • 1997  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3188-3190 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The room-temperature absorption coefficient and ordinary refractive index for a ∼0.4-μm-thick p-type wurtzite Al0.09Ga0.91N epitaxial layer were determined via optical transmission measurements. The layer was grown by metal organic chemical vapor deposition and heavily doped (∼5×1019 cm−3) with Mg. Additional measurements of the refractive index by prism coupling to the layer confirmed the transmission results. The low-temperature AlN buffer layer altered the expected interference fringes of the transmission spectrum below the band-gap energy and had to be accounted for in the analysis. The absorption coefficient exhibited band-tail effects and had a reduced slope near band-gap energy as compared to undoped GaN. Using a detailed balance argument, the reduced slope was consistent with the lack of a peak in the continuous-wave photoluminescent emission. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1196-1203 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 67-69 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dispersion of the ordinary and extraordinary indices of refraction for wurtzite AlxGa1−xN epitaxial layers with x=0.00, 0.04, 0.08, 0.11, and 0.20 in the range of wavelengths 457〈λ〈980 nm were measured via a prism-coupled waveguide technique. The quantitative accuracy of x is ±10% and the accuracy of the refractive indices is ∼±0.01. The dispersion is found to be well described by a 1st-order Sellmeier dispersion formula. A simple functional form is presented that allows calculation of the refractive indices as functions of x and λ. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-5196
    Keywords: Key words Internal cerebral vein thrombosis ; Sinovenous thrombosis ; Colitis ulcerosa ; Trauma ; Schlüsselwörter Hirnvenenthrombose ; Sinusthrombose ; Trauma ; Colitis ulcerosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Venöse Abflußstörungen des Gehirns werden mit unterschiedlicher Häufigkeit im Obduktionsgut aufgeführt. Neben entzündlichen Prozessen, hämorheologischen Störungen und Neoplasien kommen bei der forensischen Begutachtung traumatische Ursachen für die Genese von Thrombosen in Frage. Berichtet wird über eine 14 Jahre alt gewordene Schülerin, die 2 1/2 Tage nach einer tätlichen Auseinandersetzung verstarb. Anamnestisch wurde von einer Colitis ulcerosa berichtet. Initial waren weder äußere Verletzungen noch neurologische Auffälligkeiten erkennbar. In der Nacht wurde sie komatös in der Klinik aufgenommen. Die kranielle computertomographische Untersuchung zeigte eine zunehmende intraventrikuläre und intrazerebrale Blutung, Zeichen der venösen Stauung und ein Hirnödem. Die Patientin verstarb im dissoziierten Hirntod. Neuropathologisch fand sich eine in Organisation stehende Thrombose des Sinus sagittalis superior, die sich in die inneren Hirnvenen fortsetzte und die durch die entzündliche Darmerkrankung verursacht war. Eine traumatische Genese war somit auszuschließen.
    Notes: Abstract Thromboses of the cerebral veins which occur at a frequency of 3.75 to 9.3% in autopsy material are caused by local or systemic inflammatory processes, hematological disorders, neoplasms or traumatic brain damage. We report on a 14-year-old girl who suffered from colitis ulcerosa during the last 4 years of life. Immediately after a brawl with a schoolboy she complained of headache and vertigo, but no physical abnormality was detected by the physician. She was admitted to the hospital after becoming comatose during the following night. On neurological examination she was comatous with a decerebrate state, the pupils were small and non-reactive to light, divergent ocular bulbi and bilateral extensor plantar responses. A cerebral computer tomogramm showed a cerebral edema and a hemorrhage in the left basal ganglia and both cerebral ventricles which subsequently increased to the right cerebral ganglia, the corpus callosum and the right cerebral hemisphere. Despite antiedematous therapy the girl died on the second day after the brawl. A neuropathology examination revealed thrombosis of the superior sagittal sinus extending to the internal cerebral veins and a bilateral hemorrhagic infarction of the thalamus and the basal ganglia with intraventricular hemorrhage. As the thrombus in the sagittal sinus showed signs of organisation, a postraumatic origin alone is improbable and a hemorrheological disorder due to colitis ulcerosa seemed to be the main cause.
    Type of Medium: Electronic Resource
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  • 5
    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
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  • 6
    ISSN: 0942-0940
    Keywords: Malignant rhabdoid tumour ; atypical teratoid/rhabdoid tumour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three cases of primary rhabdoid tumour of the CNS (RT-CNS) are presented. In case 1 a hemispheric tumour developed in a 10.5 months old girl, who survived for 6 months after incomplete resection, radio- and polychemotherapy. Case 2 was a 4 years and 8 months old boy with a large IIIrd ventricle tumour, who died of leptomeningeal tumour dissemination 7 months after diagnosis despite radiotherapy. In case 3 a pineal mass occurring in a 14 month old female was radioresistant and totally exstirpated. The child died due to tumour recurrence two months later. Autopsy examination revealed widespread leptomeningeal dissemination. All three cases fulfilled light and electron microscopic criteria of RT-CNS including abundant eosinophilic cytoplasm, vesicular nuclei with large nucleoli and conspicuous anti-vimentin positive filaments. Extensive immunohistochemical studies showed expression of epithelial (EMA, KL1), macrophage (alpha-1 antichymotrypsin), neuro-ectodermal (GFAP, NSE, β-tubulin III) and myogenic markers (desmin, actin). Different stress proteins (alpha-B crystallin, HSP70) were also expressed. Tumour cells showed a proliferation (MIB1) index of 28.4% (case 1) and 33.4% (case 2). From our study it can be concluded that RT-CNS reveals significant immuno-morphological heterogeneity thus supporting the view that it is not a specific pathological entity but merely a phenotypic appearance of different neoplasms, some of which are linked to primitive neuro-ectodermal tumours.
    Type of Medium: Electronic Resource
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  • 7
    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
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  • 8
    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
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  • 9
    ISSN: 1439-0973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The epididymal, testicular, and prostatic tissue penetration of sparfloxacin, a new quinolone, was assessed in a rat model of acute epididymitis. Seventy-two hours after injection of 0.1 ml (106 cfu/ml) of anEscherichia coli suspension into the right epididymis via the right ductus deferens, a single oral dose of sparfloxacin 50 mg/kg body weight was administered. One, 2, 4, 8, 12, and 24 h after administration the animals were sacrificed and the sparfloxacin concentrations and “areas under the curve” (AUC0–24) in both epididymides, both testes, the prostate gland and in the serum were measured by bioassay. The highest mean AUC0–24 was found in the prostate gland, followed by left epididymis, right epididymis, serum, right testis, and left testis (190, 79, 60, 28, 12, and 9 mg/kg×h, respectively). Though there was no statistically significant difference in the sparfloxacin concentration of both epididymides (p=0.09), the mean AUC0–24 was significantly higher in the non-infected left epididymis (p〈0.0001). The AUC0–24 and sparfloxacin concentrations of the right infected epididymis were significantly higher than those observed in the serum (p〈0.0001). In both testes, the AUC0–24 and sparfloxacin concentrations were lower than in the serum (p〈0.0001), however, the concentration exceeded the MIC tenfold for approximately 20 h. It is concluded that the pharmacokinetic properties of sparfloxacin (goodin vitro activity, high penetration into the prostate gland, testes, infected and non-infected epididymides) make this drug a recommendable choice for the initial treatment of acute epididymitis caused byE. coli.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 288 (1997), S. 539-544 
    ISSN: 1432-0878
    Keywords: Key words: Testis ; hsp60 ; Infertility ; Spermatogonia ; Immunohistochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The immunohistochemical localization of heat-shock protein 60 (hsp60) was investigated in testicular biopsies obtained from 121 adult men with disturbed fertility. In normal unaffected tubules, hsp60 immunoreactivity was localized to spermatogonia, primary spermatocytes and Sertoli cells. In spermatogonia, cytosolic and mitochondrial labelling could be differentiated. In general, the number of stained spermatogonia decreased with the loss of spermatogenic function. A significant (P〈0.01) reduction of stained spermatogonia was observed in testes with maturation arrest of spermatogenesis at the level of primary spermatocytes (30.2±21.6%) compared with testes exhibiting normal spermatogenesis. In addition, the decrease in the score correlated significantly with the diminution of cytosolic hsp60 immmunolabelling (coefficient r=0.25, P=0.03). There was a significant difference (P〈0.01) in the percentage of cytosolic-stained spermatogonia in testes with a score equal to or greater than 5 (14.7±9.8%) and a score less than 5 (8.9±6.9%). These observations suggest that a low level of hsp60 expression in spermatogonia may lead to a different pattern of protection, which in turn could be involved in low spermatogenic efficiency.
    Type of Medium: Electronic Resource
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