| 1. |
- Hilson, P., et al.
(författare)
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Versatile gene-specific sequence tags for Arabidopsis functional genomics : Trancript profiling and reverse genetics applications
- 2004
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 14:10B, s. 2176-2189
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Tidskriftsartikel (refereegranskat)abstract
- Microarray transcript profiling and RNA interference are two new technologies crucial for large-scale gene function studies in multicellular eukaryotes. Both rely on sequence-specific hybridization between complementary nucleic acid strands, inciting us to create a collection of gene-specific sequence tags (GSTs) representing at least 21,500 Arabidopsis genes and which are compatible with both approaches. The GSTs were carefully selected to ensure that each of them shared no significant similarity with any other region in the Arabidopsis genome. They were synthesized by PCR amplification from genomic DNA. Spotted microarrays fabricated from the GSTs show good dynamic range, specificity, and sensitivity in transcript profiling experiments. The GSTs have also been transferred to bacterial plasmid vectors via recombinational cloning protocols. These cloned GSTs constitute the ideal starting point for a variety of functional approaches, including reverse genetics. We have subcloned GSTs on a large scale into vectors designed for gene silencing in plant cells. We show that in planta expression of GST hairpin RNA results in the expected phenotypes in silenced Arabidopsis lines. These versatile GST resources provide novel and powerful tools for functional genomics.
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| 2. |
- Leon, R., et al.
(författare)
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Defect states in red-emitting InxAl1-xAs quantum dots
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:8
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Tidskriftsartikel (refereegranskat)abstract
- Optical and transport measurements carried out in pn diodes and Schottky barriers containing multilayers of InAlAs quantum dots embedded in AlGaAs barriers show that while red emission from quantum dot (QD) states is obtained at similar to1.8 eV, defect states dominate the optical properties and transport in these quantum dots. These defects provide nonradiative recombination paths, which shortens the carrier lifetimes in QD's to tens of picoseconds (from similar to1 ns) and produce deep level transient spectroscopy (DLTS) peaks in both p and n type structures. DLTS experiments performed with short filling pulses and bias dependent measurements on InAlAs QD's on n-AlGaAs barriers showed that one of the peaks can be attributed to either QD/barrier interfacial defects or QD electron levels, while other peaks are attributed to defect states in both p and n type structures.
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| 3. |
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| 4. |
- Leon, Rosa, et al.
(författare)
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Dislocation-induced spatial ordering of InAs quantum dots : Effects on optical properties
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:9, s. 5826-5830
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Tidskriftsartikel (refereegranskat)abstract
- Misfit dislocations were used to modify the surface morphology and to attain spatial ordering of quantum dots (QDs) by molecular beam epitaxy. Effects of anneal time and temperature on strain-relaxed InxGa1-xAs/GaAs layers and subsequent spatial ordering of InAs QDs were investigated. Photoluminescence (PL) and time-resolved PL was used to study the effects of increased QD positional ordering, increased QD uniformity, and their proximity to dislocation arrays on their optical properties. Narrower inhomogeneous PL broadening from the QDs ordered on dislocation arrays were observed, and differences in PL dynamics were found.
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| 5. |
- Leon, R., et al.
(författare)
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Effects of proton irradiation on luminescence emission and carrier dynamics of self-assembled III-V quantum dots
- 2002
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 49:6, s. 2844-2851
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Tidskriftsartikel (refereegranskat)abstract
- The effects of proton irradiation (1.5 MeV) on photoluminescence intensities and carrier dynamics were compared between III-V quantum dots and similar quantum well structures. A significant enhancement in radiation tolerance is seen with three-dimensional (3-D) quantum confinement.. Measurements were carried out in different quantum dot (QD) structures, varying in material (InGaAs/GaAs and InAlAS/AlGaAS), QD surface density (4 x 10(8) to 3 x 10(10) cm(-2)), and substrate orientation [(100) and (311) B]. Similar trends were observed for all QD samples. A slight increase in PL emission after low to intermediate proton doses, are also observed in InGaAs/GaAs (100) QD structures. The latter is explained in terms of more efficient carrier transfer from the wetting layer via radiation-induced defects.
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| 6. |
- Leon, R, et al.
(författare)
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Electron irradiation effects on nanocrystal quantum dots used in bio-sensing applications
- 2004
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 51:6, s. 3186-3192
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Tidskriftsartikel (refereegranskat)abstract
- Effects of low energy electron irradiation (5-30 keV) on some of the optical properties of CdSe nanocrystals are examined. Degradation in luminescence intensities are measured and compared for inorganic nanocrystals coated in trioctylphosphine oxide (TOPO) and biologically compatible CdSe nanocrystals coated in mercaptoacetic acid (MAA), as well as CdSe-MAA nanocrystals conjugated with the protein Streptavidin. Electron beam effects are investigated using the technique of cathodolu-minescence, which is seen to induce significant degradation in nanocrystal related fluorescence in all nanocrystals. Varying beam energy and sample temperatures showed faster degradation at cryogenic temperatures and a higher susceptibility to low beam energies in protein conjugated nanocrystals.
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| 7. |
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| 8. |
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| 9. |
- Marcinkevicius, Saulius, et al.
(författare)
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Carrier capture and relaxation in quantum dot structures with different dot densities
- 2000
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Ingår i: Microelectronic Engineering. - 0167-9317 .- 1873-5568. ; feb-51, s. 79-83
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Tidskriftsartikel (refereegranskat)abstract
- Carrier dynamics has been measured by time-resolved photoluminescence in self-assembled InGaAs/GaAs quantum dot structures with dot density of the order of 10(8) to 10(10) cm(2). The time of carrier transfer into a dot, which is in the region from 2 to 20 PS, has been found to decrease with increasing quantum dot density. The temperature and photoexcited carrier density dependencies of the carrier transfer times suggest that potential barriers at the barrier, wetting layer and quantum dot interfaces hinder carrier capture in low-density quantum dot structures.
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| 10. |
- Marcinkevicius, Saulius, et al.
(författare)
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Changes in carrier dynamics induced by proton irradiation in quantum dots
- 2002
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 314:04-jan, s. 203-206
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Tidskriftsartikel (refereegranskat)abstract
- The effects of proton irradiation on carrier dynamics were investigated by time-resolved photoluminescence on different InGaAs/GaAs quantum-dot (QD) structures varying in QD surface density and substrate orientation, as well as thin InGaAs quantum wells. The carrier lifetimes in the dots are much less affected by proton irradiation than in the wells. Decrease in lifetimes of only 40 percent at the highest proton dose are observed in some of the QDs, whereas an similar to20 to similar to40-fold decrease is observed in the wells. Similar trends were observed for all quantum dot samples.
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