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  • 1
    Digitale Medien
    Digitale Medien
    Magneto-optical studies of GaN and GaN/AlxGa1−xN: Donor Zeeman spectroscopy and two dimensional electron gas cyclotron resonance (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8007-8010 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magneto-optical experiments have been performed on free and bound electrons in GaN films and GaN/AlGaN heterojunctions. Cyclotron resonance of two dimensional electron gas in GaN/ AlxGa1−xN heterojunctions has yielded m* = 0.23 m0, x-dependent scattering times consistent with values from transport measurements, and an apparent unexplained level crossing at 70 cm−1. Infrared absorption of doped GaN films has shown that the binding energy of Si donors, 29.0 meV, is much smaller than that of residual donors, in agreement with transport measurements, thus suggesting donor spectroscopy as a useful technique for defect/impurity qualitative analysis. Zeeman effect of the donor spectra has been used to determine the GaN low frequency dielectric constant, ε0 = 10.4. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.362351
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  • 2
    Digitale Medien
    Digitale Medien
    Increase conductivity in UNiSn with the application of magnetic fields : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4928-4930 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on the frequency dependent conductivity of the modified Huesler alloy UNiSn in the antiferromagnetic state and in the presence of a magnetic field. UNiSn is paramagnetic above 43 K and has a semiconducting gap of about 65 meV. Below 43 K, the compound is in an itinerant antiferromagnetic state. The reflectance of UNiSn is measured from 4 meV to 0.4 eV and in fields up to 16 Tesla. At 5 K, there is a shift in spectral weight from the gap region to lower frequencies as the applied magnetic field is increased. This shift in spectral weight gives rise to increase conductivity with applied field in the metallic state. However, the gap value is unaffected by the field. No field dependence is observed for the isostructural compound, ThNiSn, which does not undergo an antiferromagnetic transition. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.364999
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  • 3
    Digitale Medien
    Digitale Medien
    Oscillatory cyclotron resonance effective mass near ν=1 and 2 in modulation-doped ZnSe/Zn1−x−yCdxMnySe (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6466-6468 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The fabrication by molecular-beam epitaxy of modulation-doped magnetic semiconductor heterostructures results in the creation of novel "magnetic" two-dimensional electron gases (2DEGs) with unusual transport properties. We report on the measurements of cyclotron resonance (CR) and effective mass in magnetic 2DEGs formed in modulation-doped ZnSe/Zn1−x−yCdxMnySe single quantum wells. Far-infrared absorption measurements are carried out at a nominal temperature of 4.2 K and in fields up to 30 T on these magnetic samples, as well as on corresponding nonmagnetic samples (ZnSe/Zn1−xCdxSe single quantum wells). The samples have carrier densities ranging from 1 to 4×1011 cm−2 and mobilities as high as 42 000 cm2/V s for the nonmagnetic samples. For the magnetic samples, the magnetic field dependence of the CR frequency shows marked oscillatory deviations from linearity in the vicinity of integer filling factors ν=2 and ν=1. For instance, compared to the nonmagnetic samples, the amplitude of the oscillations in the effective mass of the magnetic samples changes by 15% at half-filling factor. This is significantly larger than similar oscillatory effective mass behavior observed in standard semiconductor 2DEGS (e.g., GaAs/GaAlAs), suggesting a qualitatively different physical origin for this phenomenon in these magnetic systems. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.372740
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  • 4
    Digitale Medien
    Digitale Medien
    Cyclotron resonance in modulation-doped ZnSe/Zn1−xCdxSe and ZnTe/CdSe single quantum wells (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3662-3664 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report low-temperature (4.2 K) cyclotron resonance measurements on high-mobility, two-dimensional electron gases in modulation-doped ZnSe/Zn1−xCdxSe (x=0.06, 0.12, and 0.24) single quantum wells, as well as in a modulation-doped ZnTe/CdSe single quantum well. These experiments carried out in magnetic fields ranging up to 17 T yield reliable measurements of the effective mass m* of conduction-band electrons in Zn1−xCdxSe alloys, including the measurement of m* in cubic CdSe. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.125421
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  • 5
    Digitale Medien
    Digitale Medien
    Superconducting free-standing thin films of YBa2Cu3Ox (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 201-202 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report a new technique of preparing unsupported thin films of YBa2Cu3Ox. These films are about 6×6 mm2 and less than half a micron thick. They were prepared via laser ablation on thin carbon films typically of order 50 μg/cm2 (∼2500 A(ring)). When the film was annealed, the carbon oxidized leaving behind a free-standing film. The film has a superconducting orthorhombic phase and an onset temperature of (approximately-equal-to)85 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.103935
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  • 6
    Digitale Medien
    Digitale Medien
    Ependymomas—an immunohistochemical study of 14 cases (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 13 (1988), S. 0 
    Details
    ISSN: 1365-2559
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2559.1988.tb02063.x
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  • 7
    Digitale Medien
    Digitale Medien
    Immunostaining for α1-antichymotrypsin and α1-antitrypsin in gliomas (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 13 (1988), S. 0 
    Details
    ISSN: 1365-2559
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Antisera to α1-antichymotrypsin, α1-antitrypsin and lysozyme were reacted with 20 cases of glioblastoma multiforme, seven anaplastic astrocytomas, eight astrocytomas, six oligodendrogliomas, four ependymomas and the cerebral cortex from six normal autopsy brains. In addition, two pleomorphic xantho-astrocytomas and two heavily lipidized malignant gliomas were similarly examined. All astrocytic lesions were confirmed with anti-GFAP antisera. Thirty astrocytic tumours (77%), four oligodendrogliomas (67%) and three ependymomas (75%) reacted positively with anti-α1-antichymotrypsin; 25 astrocytic tumours (64%), three oligodendrogliomas (50%) and three ependymomas (75%) showed positive staining for α1-antitrypsin. The pattern of staining with either of these two markers did not correlate with tumour grading. None of the gliomas examined stained positively with anti-lysozyme. Non-neoplastic glial elements did not react with any of the three antisera. The results of this study suggest that staining for α1-antichymotrypsin and α1-antitrypsin is of little value in the differential diagnosis of neuroepithelial or mesenchymal lesions in the brain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2559.1988.tb02005.x
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  • 8
    Digitale Medien
    Digitale Medien
    Intracranial olfactory neuroblastoma mimicking carcinoma: report of two cases (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 12 (1988), S. 0 
    Details
    ISSN: 1365-2559
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Two cases of olfactory neuroblastoma which presented clinically as intracranial lesions are described. Prominent features of epithelial differentiation were present, which led to initial diagnoses of poorly differentiated carcinoma. The true nature of the lesions was only established subsequently by careful histological examination, immunohistochemistry and electron microscopy. The potential towards epithelial differentiation in such tumours was emphasized and certain new histological features were described, including a biphasic epithelial and stromal pattern, papillae formation and positive staining for cytokeratin. These two cases underline the importance of exhaustive examination of poorly differentiated epithelial-like lesions of the frontal lobes by conventional histology, immunohistochemistry and electron microscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2559.1988.tb01954.x
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  • 9
    Digitale Medien
    Digitale Medien
    Microcystic meningiomas—an unusual morphological variant of meningiomas (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 14 (1989), S. 0 
    Details
    ISSN: 1365-2559
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Nine cases of microcystic meningiomas, a distinct morphological variant of meningiomas, are reported. They are characterized by a vacuolated and myxomatous histological appearance with multiple cystic spaces lined by stellate-shaped tumour cells. Immunohistochemically, they shared a similar pattern of positive staining for epithelial membrane antigen and vimentin with other meningiomas. Their unusual histological features might lead to problems in differential diagnosis from other intracranial tumours, including schwannomas, chordomas, astrocytomas and angioblastic meningiomas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2559.1989.tb02109.x
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  • 10
    Digitale Medien
    Digitale Medien
    Cytokeratin immunoreactivity in gliomas (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 14 (1989), S. 0 
    Details
    ISSN: 1365-2559
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Monoclonal antibodies (AE1/3, CAM 5.2 and PKK-1) and polyclonal antisera against the cytokeratin proteins were reacted with a range of astrocytic tumours, oligodendrogliomas and ependymomas. Seven of 12 cases (58%) of glioblastoma multiforme, five of eight (63%) anaplastic astrocytomas and two of five (40%) well-differentiated astrocytomas were immunoreactive with AE1/3 but not with the other anti-cytokeratin antibodies. In oligodendrogliomas, AEl/3 stained isolated astrocyte-like cells as well as scattered neoplastic oligodendrocytes in four of eight cases (50%) cases. Four ependymomas were negative for all cytokeratin markers examined. The immunostaining of astrocytomas and oligodendrogliomas with AE1/3 might represent co-expression of cytokeratin with glial fibrillary acidic protein by gliomas and calls for caution in the use of these antibodies in the differential diagnosis between gliomas and carcinomas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2559.1989.tb02164.x
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