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- Willander, Magnus, et al.
(författare)
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Optical properties of InAs quantum dots
- 2002
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Ingår i: Acta Physica Polonica. A. - : Polish Academy of Sciences Warsaw. - 0587-4246 .- 1898-794X. ; 102:4-5, s. 567-576
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Tidskriftsartikel (refereegranskat)abstract
- InAs quantum dots grown on GaAs substrate were investigated by optical spectroscopy. We particularly emphasized on the photoluminescence intensity, the stability of the photoluminescence intensity versus temperatures and wavelength of the InAs dot emission at various thermal treatments and different structures. We found that hydrogen can strongly passivate nonradiative centers without causing any structure degradation, and both n- and p-type modulation doping can reduce the decrease in the photoluminescence intensity when the sample temperature increases from the helium temperature to room temperature. The emission wavelength and the efficiency of the InAs quantum dots can also be manipulated by choosing proper materials of cap layer.
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| 2. |
- Hedera, P., et al.
(författare)
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Spastic paraplegia, ataxia, mental retardation (SPAR) : A novel genetic disorder
- 2002
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Ingår i: Neurology. - : American Academy of Neurology. - 0028-3878 .- 1526-632X. ; 58:3, s. 411-416
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To describe a kindred with a dominantly inherited neurologic disorder manifested either as uncomplicated spastic paraplegia or ataxia, spastic paraplegia, and mental retardation.Methods: Neurologic examinations and molecular genetic analysis (exclusion of known SCA and HSP genes and loci; and trinucleotide repeat expansion detection [RED]) were performed in six affected and four unaffected subjects in this family. MRI, electromyography (EMG), and nerve conduction studies were performed in three affected subjects.Results: The phenotype of this dominantly inherited syndrome varied in succeeding generations. Pure spastic paraplegia was present in the earliest generation; subsequent generations had ataxia and mental retardation. MRI showed marked atrophy of the spinal cord in all patients and cerebellar atrophy in those with ataxia. Laboratory analysis showed that the disorder was not caused by mutations in genes that cause SCA-1, SCA-2, SCA-3, SCA-6, SCA-7, SCA-8, and SCA-12; not linked to other known loci for autosomal dominant ataxia (SCA-4, SCA-5, SCA-10, SCA-11, SCA-13, SCA-14, and SCA-16); and not linked to known loci for autosomal dominant hereditary spastic paraplegia (HSP) (SPG-3, SPG-4, SPG-6, SPG-8, SPG-9, SPG-10, SPG-12, and SPG-13) or autosomal recessive HSP SPG-7. Analysis of intergenerational differences in age at onset of symptoms suggests genetic anticipation. Using RED, the authors did not detect expanded CAG, CCT, TGG, or CGT repeats that segregate with the disease.Conclusions: The authors describe an unusual, dominantly inherited neurologic disorder in which the phenotype (pure spastic paraplegia or spastic ataxia with variable mental retardation) differed in subsequent generations. The molecular explanation for apparent genetic anticipation does not appear to involve trinucleotide repeat expansion.The spinocerebellar ataxias (SCA) and hereditary spastic paraplegias (HSP), although clinically heterogeneous, typically are discerned as distinct syndromes: insidiously progressive ataxia of SCA typically is distinct from the insidiously progressive spastic gait disturbance of HSP.1-5⇓⇓⇓⇓ We identified a kindred with a unique, dominantly inherited neurologic disorder with features of both HSP and spastic ataxia. The most remarkable feature was the observation that different individuals exhibited different phenotypes within this family. Whereas affected members of the oldest generations exhibited pure spastic paraplegia, affected members in the younger generations exhibited cerebellar ataxia, lower extremity spasticity, and variable mental retardation and subtle dystonia. We designate this novel Spastic Paraplegia, Ataxia, mental Retardation syndrome as SPAR. In this report, we describe the clinical features of this SPAR index family and present our findings supporting that SPAR is genetically distinct from known forms of autosomal dominant HSP and SCA and is not caused by an expanded trinucleotide repeat.
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| 3. |
- Holtz, Per-Olof, 1951-, et al.
(författare)
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Impurities Confined in Quantum Wells
- 2004. - 3
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Quantum Wells, Wires and Dots Second Edition: Theoretical and Computational Physics of Semiconductor Nanostructuresprovides all the essential information, both theoretical and computational, for complete beginners to develop an understanding of how the electronic, optical and transport properties of quantum wells, wires and dots are calculated. Readers are lead through a series of simple theoretical and computational examples giving solid foundations from which they will gain the confidence to initiate theoretical investigations or explanations of their own.Emphasis on combining the analysis and interpretation of experimental data with the development of theoretical ideasComplementary to the more standard textsAimed at the physics community at large, rather than just the low-dimensional semiconductor expertThe text present solutions for a large number of real situationsPresented in a lucid style with easy to follow steps related to accompanying illustrative examples
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| 4. |
- Kerns, JM, et al.
(författare)
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A comparison of peripheral nerve regeneration in acellular muscle and nerve autografts
- 2003
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Ingår i: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery. - : Informa UK Limited. - 1651-2073 .- 0284-4311. ; 37:4, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- Regeneration of the rat sciatic nerve through acellular muscle and nerve autografts was evaluated 6-28 days postoperatively by the sensory pinch test, immunocytochemical staining for neurofilaments, and light and electron microscopy. Data points generated by the pinch test were plotted against postoperative time periods and by the use of regression analysis the initial delay period for muscle grafts was determined to 10.3 days. This value was similar to that previously published for acellular nerve grafts (9.5 days), but significantly longer than that for fresh nerve grafts (3.6 days). The calculated regeneration rate (slope of the regression line) for muscle grafts (1.8 mm/day) did not differ significantly ( p >0.05) from that calculated for acellular nerve grafts (2.1 mm/day) or for fresh nerve grafts (1.5 mm/day). The front of regenerating axons shown by axonal neurofilament staining confirmed the pinch test results. Both types of acellular grafts were repopulated with host non-neuronal cells and the muscle graft contained occasional ectopic muscle fibres. Remnants of graft basal laminae were evident at the ultrastructural level. These results indicate the suitability of either acellular muscle or nerve grafts for nerve repair despite their prolonged initial delay periods compared with conventional fresh nerve grafts.
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| 10. |
- Zhao, Q.X., et al.
(författare)
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Dynamic properties of radiative recombination in p-type d-doped layers in GaAs
- 2001
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 63
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Tidskriftsartikel (refereegranskat)abstract
- We present an optical study of thin Zn-doped GaAs layers embedded in bulk GaAs, grown by metal-organic vapor-phase-epitaxy by means of stationary and time-resolved optical spectroscopy. The concentration of the Zn acceptors was aimed at 2×1020/cm3 in 4-nm-wide doping regions. The intensity of the optical radiative transition (so called the F emission) appearing in photoluminescence spectra was found to be related to holes confined at doping regions. The F emission shows a strong dependence on excitation intensity and temperature. The energy position varies from 1.46 to 1.49 eV as the excitation density changes from about 40 mW/cm2 to 23 W/cm2. The dynamic properties of the F-emission band have been studied by time-resolved spectroscopy. The F emission shows a nonexponential decay character. The decay time of the F emission exhibits a strong dependence on the detection energy within the F-emission band. The decay time becomes longer as the detection energy is redshifted.
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