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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2681-2686 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical characteristics of TiSix contacts to nitrogen implanted 6H-SiC are investigated using linear transmission line method structures at temperatures up to 673 K. Nitrogen is implanted into a p-type (NA(approximate)1×1016 cm−3) 6H-SiC epilayer at 500 °C and activated at 1700 °C, resulting in an activated donor concentration of ND=5×1019 cm−3 to a depth of 300 nm with a reduced electrically active surface concentration of about ND(approximate)5×1018 cm−3. Sputtered titanium silicide is used as contact metallization. Five different contact formation temperatures TA ranging from 900 to 1150 °C are applied to the samples in order to investigate the specific contact resistance ρc. Whereas an anneal of at least 950 °C is necessary to achieve an ohmic contact behavior, samples annealed at 1150 °C show specific contact resistance of 7×10−6 Ω cm2 at room temperature, which decreases monotonically to 4×10−6 Ω cm2 at 673 K. The sheet resistance Rs (resistivity ρs) of the n+-implanted layer is 521 Ω/(square, open) (15.6×10−3 Ω cm) at 303 K. Up to 573 K, Rs declines to 354 Ω/(square, open) (10.6×10−3 Ω cm) as the incomplete ionization of the nitrogen dopants dominates the temperature behavior. Above 573 K, the reduction of the electron mobility via phonon scattering dominates, and Rs increases to 363 Ω/(square, open) (10.9×10−3 Ω cm) at 673 K. From the resistivity as a function of temperature, the low field mobility μ0 is 149 cm2/V s at 300 K, and the temperature exponent α=1.62 of the power law dependence can be deduced. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 29 (1996), S. 0 
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report on two cases of low grade follicle centre cell lymphoma with a pronounced parafollicular monocytoid/marginal zone B-cell component. One patient had a history of preceeding follicular high grade B-cell lymphoma of centroblastic type showing the same light chain restriction and identical immunoglobulin heavy chain gene rearrangement as the low grade lymphoma diagnosed 15 months later. Morphologically, in both cases the two constituents of the low grade tumours were clearly distinguishable. Immunohistochemically, the follicular component strongly expressed bcl-2 protein in contrast to a weak staining of the marginal zone B-cell component. Performing PCR, a rearrangement of the major breakpoint region of bcl-2 was not found. Identical light chain restriction of the follicular and the monocytoid B-cell/marginal zone components strongly indicates a clonal relationship between them. A monocytoid/marginal zone B-cell component in follicular lymphoma probably results from differentiation of the follicle centre cells and does not indicate a composite lymphoma.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Gliom ; Astrozytom ; Oligodendrogliom ; Kavernom ; Metastase ; Kortex ; Motorik ; Sprache ; Neuromonitoring ; Neuropsychologie ; Key words Glioma ; Astrocytoma ; Oligodendroglioma ; Cavernoma ; Metastasis ; Brain ; Cortex ; Sensorimotor ; Language ; Speech ; Neuromonitoring ; Neuropsychology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We report on 30 cases where we have used cortical stimulation mapping to define the areas representing sensorimotor, language and speech functions under local anesthesia to facilitate resection of space-occupying lesions near these areas. Under the simplistic concept that Broca’s area lies in the frontal operculum (inferior frontal gyrus) and that Wernicke’s area is located in the posterior perisylvian area (superior temporal, angular and supramarginal gyri), we found language and speech function to be represented outside these areas in up to 4 stimulation sites of 15 patients. The results of cortical stimulation mapping were therefore essential to decide on the optimal access route to the lesions that were located subcortically and on the optimal resection plane in gliomas. After the limits of these areas and of the lesions had been established with stimulation mapping and with intrasurgical microscopic smear preparations, respectively, lesions were safely removed under continuous monitoring of sensorimotor, language and speech function. Immediately after surgery we encountered language and speech deficits in 9 patients (30%), which resolved completely in 5 and inclompletely in 4 instances. Thus, language functions were normal in 26 patients (87%) at the end of the follow-up period. It is concluded that use of this technique allows safe and extensive resection of lesions that would otherwise have been considered hazardous to remove or inexcisable.
    Notes: Zusammenfassung 1990 bis 1994 haben wir 30 Patienten mit Prozessen nahe den kortikalen Sprachzentren in Lokalanästhesie mit Analgosedierung operiert. Die kortikalen Zentren von Sensomotorik, Sprache und Sprechen wurden mittels elektrischer Reizung (kortikales Mapping) identifiziert, die Raumforderung während der selben Operation mikrochirurgisch entfernt. Geht man von der vereinfachten Vorstellung aus, daß das Broca-Sprachzentrum im frontalen Operkulum und das Wernicke-Sprachzentrum um die hinteren Anteile der Sylvischen Fissur liegen, so fand sich bei 15 Patienten auch Sprachrepräsentation an bis zu 4 Reizorten ausserhalb dieser Sprachzentren. Die Ergebnisse des kortikalen Mapping waren deshalb entscheidend für die Wahl des Zugangsweges zu Prozessen unter der Hirnoberfläche und für die Wahl der Resektionsgrenzen bei den Gliomen. Die Tumorresektion wurde beendet, wenn die Resektionsränder zytologisch tumorfrei waren, der Prozeß zu nahe an „eloquente” Hirnareale heranreichte oder wenn Störungen von Sprache, Sprechen oder Körpermotorik auftraten. Unmittelbar postoperativ kam es bei 9 Patienten (30%) zu einem variabel ausgeprägten neuropsychologischen Defizit, das sich bis zur Abschlußuntersuchung bei 5 dieser Patienten normalisierte. Mithin fand sich bei 26 (87%) der 30 Patienten am Ende der Nachuntersuchungszeit kein faßbares neuropsychologisches Defizit. Dies bedeutet, daß die Resektion bis an die Grenzen des funktionell Statthaften gegangen war, daß diese Grenzen aber zumeist nicht überschritten wurden.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1437-9813
    Keywords: Key words Hodgkin's disease ; Recurrent mediastinal mass ; Gallium-67 SPECT ; Thymic rebound ; Chemoradiotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The case of an 11-year-old girl with mediastinal stage III B-E Hodgkin's disease is described. She achieved complete remission with combined chemoradiotherapy according to the Swiss Pediatric Oncology Group-HD Protocol 1985. Six months after all therapy was stopped, a slowly growing retrosternal mass was detected. Computed tomography (CT) and gallium-67 single-photon emission CT (SPECT) could not elucidate the true origin of the tumor, nor did ultrasound-guided transthoracic fine-needle puncture. Open biopsy with histologic examination of the lesion has successfully identified the mass as thymic hyperplasia, a rebound immunologic reaction after chemoradiotherapy that mimicked tumor regrowth.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1437-9813
    Keywords: Hodgkin's disease ; Recurrent mediastinal mass ; Gallium-67 SPECT ; Thymic rebound ; Chemoradiotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The case of an 11-year-old girl with mediastinal stage III B-E Hodgkin's disease is described. She achieved complete remission with combined chemoradiotherapy according to the Swiss Pediatric Oncology Group-HD Protocol 1985. Six months after all therapy was stopped, a slowly growing retrosternal mass was detected. Computed tomography (CT) and gallium-67 single-photon emission CT (SPECT) could not elucidate the true origin of the tumor, nor did ultrasound-guided transthoracic fine-needle puncture. Open biopsy with histologic examination of the lesion has successfully identified the mass as thymic hyperplasia, a rebound immunologic reaction after chemoradiotherapy that mimicked tumor regrowth.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0942-0940
    Keywords: Electrical stimulation ; nerve ; neurography ; neuromonitoring ; brain stem ; cauda equina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To facilitate use of various stimulation modes for intra-operative monitoring during neurosurgical procedures, we designed and produced a variable stimulation system that consists of a coaxial bipolar flush-tip insulated stimulation electrode, and a switch box to administer monopolar or bipolar stimulation through the same stimulation electrode. The electrode is composed of components that are readily available, so that its construction can be duplicated by others at minimal expense. For mapping of neural tissue during surgical procedures, we use the monopolar stimulation mode to identify relative large areas around the site of stimulation which are free of motor nerve fibres. The bipolar stimulation mode is most useful for precise localization of motor nerve fibres and in distinguishing motor from non-motor fibres.
    Type of Medium: Electronic Resource
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