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  • 1
    Electronic Resource
    Electronic Resource
    Instantaneous optical modulation in bulk GaAs semiconductor microcavities (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3779-3781 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Picosecond pump–probe experiments at room temperature on a bulk GaAs microcavity are presented. The microcavity device is designed to adjust the cavity mode energy 15 meV below the band gap energy of the intracavity bulk GaAs material. For low pump-energy densities (∼μJ/cm2), ultrafast modulation of the reflectivity is demonstrated due to the purely coherent refractive index change. A 5:1 contrast ratio is achieved and shows the potential of the semiconductor microcavities for implementation in ultrafast all optical switching. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1379783
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  • 2
    Electronic Resource
    Electronic Resource
    Spatial modulation of the dielectric function using free carriers and/or coherent effects in quantum-well semiconductor microcavity (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3056-3058 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results on picosecond degenerate four-wave mixing in semiconductor microcavity are presented. The device is made of GaInAs/GaInAsP multiple quantum wells enclosed in an asymmetric Fabry–Perot microcavity 80%–98%. For incident photon energies below the excitonic energy, the spatial modulation of the dielectric function can be generated by free carriers and/or coherent effects. We show that the last one can be significant; an input diffraction efficiency of 2% with only 1 μJ/cm2 pump fluence is achieved. This result demonstrates a new way to obtain ultrafast, sensitive, and low-dissipative devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124063
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  • 3
    Electronic Resource
    Electronic Resource
    Photorefractive p-i-n diode quantum well operating at 1.55 μm (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3576-3578 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate the performance of a semiconductor photorefractive p-i-n diode operating at 1.55 μm in the longitudinal quantum-confined Stark geometry. The device structure consists of a semi-insulating InP–GaInAs(P) multiple quantum well, sandwiched between two trapping regions, and embedded in a p-n junction. In this structure, the measured output diffraction efficiency reaches 0.6%. This value is close to the output diffraction efficiency value estimated from electroabsorption measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116642
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  • 4
    Electronic Resource
    Electronic Resource
    Fe-doped InGaAs/InGaAsP photorefractive multiple quantum well devices operating at 1.55 μm (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3591-3593 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results on semi-insulating photorefractive multiple quantum well (MQW) devices operating without trapping layers are reported. The device structure consists of a MQW doped with Fe (1017 cm−3) isolated from the doped contact by intrinsic standoff layers. The photocarriers generated by the pump pulse are trapped in the MQW and screen the applied electric field in the MQW. Output diffraction efficiency of 0.2% is measured in a nondegenerate four-wave-mixing configuration and the rise time of the diffraction signal reaches 200 ns. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119242
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  • 5
    Electronic Resource
    Electronic Resource
    Photorefractive multiple quantum well device using quantum dots as trapping zones (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1575-1577 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results on the optical properties of a GaInAs/GaInAsP multiple quantum well photorefractive device operating at 1.55 μm in the longitudinal quantum-confined Stark geometry are reported. Self-assembling quantum dots (SAQDs) have been used in this device to trap the photocarriers in two regions out of the multiple quantum well. An efficient screening of applied electric field and the possibility to reduce the lateral diffusion of carriers with SAQDs are demonstrated. Finally, degenerate four-wave mixing measurements were performed in this device. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118621
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  • 6
    Electronic Resource
    Electronic Resource
    Pineal cyst: normal or pathological? (1993)
    Springer
    Neuroradiology 35 (1993), S. 251-253 
    Details
    ISSN: 1432-1920
    Keywords: Pineal gland ; Cyst ; Pineal cyst ; Normal variant ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Review of 500 consecutive MRI studies was undertaken to assess the frequency and the appearances of cystic pineal glands. Cysts were encountered in 2.4% of cases. Follow-up examination demonstrated no change in these cysts and they were considered to be a normal variant. Size, MRI appearances and signs associated with this condition are reported in order to establish criteria of normality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00602604
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  • 7
    Electronic Resource
    Electronic Resource
    Lipomyeloschisis associated with thoracic syringomyelia and Chiari I malformation (1993)
    Springer
    Neuroradiology 35 (1993), S. 375-377 
    Details
    ISSN: 1432-1920
    Keywords: Chiari malformation ; Dysraphism ; Lipoma ; Lipomyelomeningocele ; Magnetic resonance imaging ; Syringomyelia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Co-existence of Chiari I malformation and myelomeningocele is uncommon. Syringomyelia, when associated with a Chiari I malformation, classically involves the cervical spinal cord. Intramedullary extension of lipoma is unusual in lipomyeloschisis. A patient with lumbar lipomyelomeningocele with tethered cord, lower thoracic syringomyelia and Chiari I malformation, shown by MRI is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588374
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  • 8
    Electronic Resource
    Electronic Resource
    Gadodiamide injection as a contrast medium for MRI of the central nervous system: a comparison with gadolinium-DOTA (1993)
    Springer
    Neuroradiology 35 (1993), S. 490-494 
    Details
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Brain ; Spine ; Contrast enhancement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The tolerance and diagnostic efficacy of a new nonionic, intravenous MRI contrast medium, gadodiamide injection (Omniscan®) are reported and compared with those of gadolinium-DOTA after completion of a double-blind, randomized, parallel study in 60 patients using a dose of 0.1 mmol/kg. Two patients were excluded from the statistical analysis after trial entrance since no contrast medium was injected. The indications for the MRI examination were known or suspected CNS lesions. Vital signs, chemical and haematological parameters were monitored. No significant abnormalities were observed, confirming the excellent tolerance of both contrast media. The usefulness of gadolinium-containing contrast media was again documented, since in 8.6% (5/58) of the patients the lesion(s) could be seen only after injection. Contrast enhancement was seen in 87.8% (43/49) of the patients with abnormal findings, and provided additional diagnostic information in 24.5% (12/49). Lack of contrast enhancement in 12.2% (6/49) of patients with abnormal findings was a significant negative finding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588702
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  • 9
    Electronic Resource
    Electronic Resource
    Gadolinium enhancement of vertebral endplates following lumbar disc surgery (1993)
    Springer
    Neuroradiology 35 (1993), S. 503-505 
    Details
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Postoperative lumbar spine ; Intervertebral discs ; Infection ; Gadolinium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Gadolinium enhancement may be normal in the vertebral endplates adjacent to previously operated intervertebral discs. To determine the frequency of this finding and to differentiate this normal healing process from early lesions due to focal infection, we studied 135 patients who had undergone surgery for herniated lumbar disc, and compared them with 249 unoperated patients with radicular symptoms and 15 with known spondylodiscitis. Hypointense foci which enhanced with gadolinium were identified in the endplates of 25 (18.5%) of the operated patients, 9 of whom required a second operation for recurrent disc herniation, at which time the absence of infection was confirmed. Gadolinium enhancement within the endplates adjacent to the operated disc occurs during normal healing after surgery. Care should be taken before invoking a diagnosis of focal infection or secondary spondylodiscitis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588706
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  • 10
    Electronic Resource
    Electronic Resource
    Stereotactic indications for neuroradiological differential diagnosis (1993)
    Springer
    Acta neurochirurgica 124 (1993), S. 31-33 
    Details
    ISSN: 0942-0940
    Keywords: MR brain ; CT brain ; cerebral angiography ; stereotactic biopsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The modern neurodiagnostic techniques of MR imaging, CT scanning and angiography provide valuable morphological information that, although highly sensitive to tumour localisation, still lacks comparable specificity as to the exact histological nature of those lesions demonstrated. Biopsy remains necessary. To patients with potentially inoperable lesions or lesions best treated by chemotherapy or irradiation, modern techniques of neurosurgery now offer the option of precise stereotactic biopsy through small twist-drill burr holes as opposed to open biopsy. The interrelationships between MR, CT, angiography and stereotactic biopsy and their respective roles in the establishment of a definitive diagnosis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01400712
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