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  • 1995-1999  (133)
  • 1995  (133)
  • Magnetic resonance imaging  (81)
  • Conference proceedings  (52)
  • 1
    Electronic Resource
    Electronic Resource
    Vacuum rabi splitting in semiconductor microcavities with applied electric and magnetic fields (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1781-1786 
    Details
    ISSN: 0392-6737
    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Electroopical effects ; Magnetooptical effects ; Photon interactions with atoms ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We describe the use of measurements of vacuum Rabi splitting to extract values for the exciton oscillator strengths in In0.13Ga0.87As-GaAs and GaAs-Al0.2Ga0.8As quantum wells. By varying both field and temperature we determine the changes in the oscillator strength in applied electric and magnetic fields. We show that these are in good agreement with the results of quantum well exciton calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457280
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Excitation energy dependence of the optical properties of InGaAs/GaAs quantum well heterostructures (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1383-1387 
    Details
    ISSN: 0392-6737
    Keywords: III–V semiconductors ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Excitons and related phenomena (including electron-hole drops) ; III–V compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report an experimental study on a large set of InGaAs/GaAs quantum well structures by means of continuous-wave photoluminescence and photoluminescence excitation. The luminescence spectrum at low temperature systematically exhibits a doublet structure whose lineshape is very sensitive to the excitation energy. Accordingly, the excitation spectra detected by monitoring the emission at the two different luminescence peaks have very different profiles, with peaks and/or dips which are not directly related to absorption resonances. As a matter of fact, the anomalies disappear when increasing the temperature or when using an optical bias with energy above the GaAs energy gap. In these cases, the excitation profiles recover the behaviour typical of 2D systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457214
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Two-photon absorption spectroscopy in ZnSe/ZnSSe strained-layer superlattices (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1635-1639 
    Details
    ISSN: 0392-6737
    Keywords: II–VI compounds and other chalcogenides ; Nonlinear optics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report two-photon absorption photoluminescence excitation (TPA-PLE) measurements in ZnSe/ZnSSe strained-layer superlattices (SLS). Polarization-dependent selection rules are observed in TPA spectra depending on the direction of the exciting field with respect to the growth axis of the SLS. Experimental exciton transition energies have found to be in good agreement with theoretical predictions considering strain and confinement effects. Furthermore by means of comparative non-linear technique the TPA coefficient has been measured at different energies and compared with theoretical predictions including quasi-bidimensional excitonic effects. A satisfactory agreement has been shown for the overall spectral behaviour and in some cases also for the TPA coefficient values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457256
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  • 4
    Electronic Resource
    Electronic Resource
    Optical transitions involving excitons in quantum wires (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1219-1228 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Optical properties of thin films surfaces and layer structures (superlattices, heterojunctions and multilayers) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We present a comprehensive discussion of the excitonic properties of V-shaped GaAs and InGaAs quantum wires grown on patterned substrates. Systematic linear and non-linear spectroscopic studies have been performed in order to clarify the impact of lateral confinement on the exciton wave function, namely: enhanced exciton binding energy, localization in magnetic field, recombination from excited states and multiphoton absorption. The careful evaluation of the electron confinement energies, based on the actual quantum wire profile obtained by TEM micrographs, including the internal piezoelectric field induced by off-diagnoal terms of strain tensor, reproduces quite well the measured one-dimensional states. Finally, application of quantum wires in a p-i-n wave guide for bistable operation is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457193
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  • 5
    Electronic Resource
    Electronic Resource
    Leukoencephalopathy with swelling in children and adolescents: MRI patterns and differential diagnosis (1995)
    Springer
    Neuroradiology 37 (1995), S. 679-686 
    Details
    ISSN: 1432-1920
    Keywords: Leukoencephalopathy ; White matter swelling ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In children, several neurological disorders are characterised by spongiform leukoencephalopathy. MRI of the brain typically shows white matter swelling, but does not enable differentiation of the various underlying disorders. The aim of this article is optimisation of the diagnostic value of MRI in leukoencephalopathy accompanied by swelling. MRI-based inclusion criteria were met by 20 patients in our database. The images were analysed using a detailed scoring list. In 13 of the 20 patients the clinical diagnosis was known (11 definite and 2 probable diagnoses). Characteristic MRI abnormalities could be defined in these patients. Of the 7 patients without a diagnosis, 5 had identical MRI abnormalities: difuse hemisphere swelling and typical cysts in frontoparietal subcortical white matter and the tips of the temporal lobes. The clinical picture was also similar in these patients, suggesting a similar disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00593394
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  • 6
    Electronic Resource
    Electronic Resource
    Leukoencephalopathy with swelling in children and adolescents: MRI patterns and differential diagnosis (1995)
    Springer
    Neuroradiology 37 (1995), S. 679-686 
    Details
    ISSN: 1432-1920
    Keywords: Key words Leukoencephalopathy ; White matter swelling ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In children, several neurological disorders are characterised by spongiform leukoencephalopathy. MRI of the brain typically shows white matter swelling, but does not enable differentiation of the various underlying disorders. The aim of this article is optimisation of the diagnostic value of MRI in leukoencephalopathy accompanied by swelling. MRI-based inclusion criteria were met by 20 patients in our database. The images were analysed using a detailed scoring list. In 13 of the 20 patients the clinical diagnosis was known (11 definite and 2 probable diagnoses). Characteristic MRI abnormalities could be defined in these patients. Of the 7 patients without a diagnosis, 5 had identical MRI abnormalities: diffuse hemisphere swelling and typical cysts in frontoparietal subcortical white matter and the tips of the temporal lobes. The clinical picture was also similar in these patients, suggesting a similar disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050179
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Acute myelopathy of unknown aetiology: a clinical, neurophysiological and MRI study of short-and long-term prognostic factors (1995)
    Springer
    Journal of neurology 242 (1995), S. 497-503 
    Details
    ISSN: 1432-1459
    Keywords: Acute myelopathy ; Magnetic resonance imaging ; Evoked potentials ; Multiple sclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Brain and spinal cord magnetic resonance imaging (MRI), multimodal evoked potentials (EPs) and cerebrospinal fluid (CSF) analysis were performed in 27 patients with acute myelopathy of unknown aetiology (AMUA), to detect the diagnostic and prognostic values of paraclinical tests at presentation. Spinal cord MRI was abnormal in 56% and brain MRI in 33% of the patients. Visual EPs were abnormal in 7%, median somatosensory EPs in 17%, tibial somatosensory EPs in 56% and motor EPs in 35% of the cases examined. Brain-stem acoustic EPs were normal in all the patients. CSF oligoclonal bands (OBs) were detected in 30% of cases. The patients were divided into subgroups according to the short-term clinical outcome (complete, partial or absent recovery). There were no significant differences among the three groups as regards MRI findings. Patients with complete recovery showed a significantly lower frequency of tibial somatosensory EP and motor EP abnormalities. According to the paraclinical findings at onset and on the basis of a long-term clinical follow-up (mean duration 24 months), 6 patients were diagnosed as having clinically definite multiple sclerosis, while 21 did not develop further neurological disturbances. Only the presence of CSF OBs was significantly more frequent in patients with definite multiple sclerosis. Our study indicates that EPs exploring spinal cord function are more powerful than spinal MRI for predicting the short-term outcome of AMUA, while the combined use of brain MRI and CSF OBs has the highest negative predictive value for the subsequent development of clinically definite multiple sclerosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00867419
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  • 8
    Electronic Resource
    Electronic Resource
    Correlation of the findings of thallium-201 chloride scans with those of other imaging modalities and histology following therapy in patients with bone and soft tissue sarcomas (1995)
    Springer
    European journal of nuclear medicine 22 (1995), S. 1232-1237 
    Details
    ISSN: 1619-7089
    Keywords: Soft tissue sarcomas ; Thallium-201 ; Magnetic resonance imaging ; Post-therapy changes ; Residual/recurrent tumors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We performed a prospective study to evaluate the imaging potential of thallium-201 as compared with other imaging modalities in differentiating residual/re-current tumors from post-therapy changes in patients with musculoskeletal sarcomas.201TI scans, magnetic resonance imaging (17), X-ray computed tomography (6) or contrast angiography (6) studies in 29 patients previously treated for musculoskeletal sarcomas were correlated with either histopathologic findings (26 patients) or 2-year clinical follow-up (three patients). All imaging studies were acquired within 2 weeks. Ratios of201T1 tumor uptake to the contralateral (28 patients) or adjacent region of interest were calculated. When qualitative interpretation was in doubt, only those cases with a ratio of 1.5 or more were considered suggestive of recurrent or residual viable tumor tissue. Residual or recurrent tumor tissue was verified in 21 patients by biopsy. All had true-positive201Tl scans while the other imaging modalities were true-positive in 20 and equivocal in one. In eight patients, there was no evidence of viable tumor tissue as proven by biopsy in five and long-term clinical follow-up in three.201Tl scan was false-positive (ratio 1.5) in one patient and true-negative in seven while the other' imaging modalities had four false-positives. The average201T1 ratios were 3.8±1.1 in the true-positive cases and 1.3±0.3 in the true-negative cases. The percentage sensitivities, specificities, and accuracy for201T1 were 100%, 87.5%, and 96.5% versus 95%, 50%, and 82.7% respectively for other imaging modalities These results indicate that201T1 scintigraphy is more accurate than other imaging modalities in differentiating residual/recurrent musculoskeletal sarcomas from post-therapy changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00801605
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  • 9
    Electronic Resource
    Electronic Resource
    The pathology of the lower leg muscles in pure forefoot pes cavus (1995)
    Springer
    Acta neuropathologica 89 (1995), S. 552-559 
    Details
    ISSN: 1432-0533
    Keywords: Key words Pes cavus ; Magnetic resonance imaging ; Pathology ; Morphometry ; Peroneus longus hypertrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Enlargement of the peroneus longus muscle is a common occurrence in patients with forefoot pes cavus, and may contribute to the cavus deformity. The present study compares the morphology of up to five lower leg muscles from 17 patients with forefoot pes cavus with those of normal muscles. Eight cases had an identifiable neurogenic cause for the cavus. In four cases of hereditary motor-sensory neuropathy, the tibialis anterior showed more severe damage than the peroneus longus. In two cases of cerebral palsy, fibre atrophy and increased oxidative enzyme activity were observed. In nine clinically idiopathic cases, the histological appearances ranged from normal to generalised fibre atrophy or hypertrophy in individual muscles. There was a trend for the mean fibre area to be greater in peroneus longus than in tibialis anterior in six of the idiopathic group of patients. The muscle cross-sectional area on magnetic resonance imaging was correlated closely with the mean fibre area measured on tissue sections. In idiopathic forefoot pes cavus, fibre hypertrophy in peroneus longus (relative to tibialis anterior) may contribute to the cavus deformity. Muscle fibre hyperplasia may contribute to the peroneal muscle enlargement in Friedreich's ataxia. In none of the cases was peroneus longus enlargement due to fat or fibrous tissue replacement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571511
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    The pathology of the lower leg muscles in pure forefoot pes cavus (1995)
    Springer
    Acta neuropathologica 89 (1995), S. 552-559 
    Details
    ISSN: 1432-0533
    Keywords: Pes cavus ; Magnetic resonance imaging ; Pathology ; Morphometry ; Peroneus longus hypertrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Enlargement of the peroneus longus muscle is a common occurrence in patients with forefoot pes cavus, and may contribute to the cavus deformity. The present study compares the morphology of up to five lower leg muscles from 17 patients with forefoot pes cavus with those of normal muscles. Eight cases had an identifiable neurogenic cause for the cavus. In four cases of hereditary motor-sensory neuropathy, the tibialis anterior showed more severe damage than the peroneus longus. In two cases of cerebral palsy, fibre atrophy and increased oxidative enzyme activity were observed. In nine clinically idiopathic cases, the histological appearances ranged from normal to generalised fibre atrophy or hypertrophy in individual muscles. There was a trend for the mean fibre area to be greater in peroneus longus than in tibialis anterior in six of the idiopathic group of patients. The muscle cross-sectional area on magnetic resonance imaging was correlated closely with the mean fibre area measured on tissue sections. In idiopathic forefoot pes cavus, fibre hypertrophy in peroneus longus (relative to tibialis anterior) may contribute to the cavus deformity. Muscle fibre hyperplasia may contribute to the peroneal muscle enlargement in Friedreich's ataxia. In none of the cases was peroneus longus enlargement due to fat or fibrous tissue replacement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571511
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    Paper (German National Licenses)
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