| 1. |
- Anand, Srinivasan, et al.
(författare)
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InP-based photonic crystal waveguide filters
- 2010
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Ingår i: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010. - 9781424471119 ; , s. 104-105
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Konferensbidrag (refereegranskat)
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| 2. |
- Anand, Srinivasan, et al.
(författare)
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InP-Based Photonic Crystal Waveguide Technology for Filtering and Sensing Applications
- 2011
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Ingår i: 2011 13TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON). - NEW YORK : IEEE. - 9781457708800
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Konferensbidrag (refereegranskat)abstract
- Photonic crystal (PhC) components in InP-based materials are of practical importance not only for their unique properties but also for integration with conventional optoelectronic components on InP substrate. Several PhC devices in the substrate approach such as filters, lasers, and waveguides have been demonstrated [1,2] and this has been possible due to the development of deep etching of PhCs in InP [3].
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| 3. |
- Jameel, Muhammad, et al.
(författare)
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A novel AP4M1 mutation in autosomal recessive cerebral palsy syndrome and clinical expansion of AP-4 deficiency
- 2014
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Ingår i: BMC Medical Genetics. - : Springer Science and Business Media LLC. - 1471-2350. ; 15, s. 133-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Cerebral palsy (CP) is a heterogeneous neurodevelopmental disorder associated with intellectual disability in one-third of cases. Recent findings support Mendelian inheritance in subgroups of patients with the disease. The purpose of this study was to identify a novel genetic cause of paraplegic CP with intellectual disability in a consanguineous Pakistani family.METHODS:We performed whole-exome sequencing (WES) in two brothers with CP and intellectual disability. Analysis of AP4M1 mRNA was performed using quantitative real-time PCR on total RNA from cultured fibroblasts. The brothers were investigated clinically and by MRI.RESULTS:We identified a novel homozygous AP4M1 mutation c.194_195delAT, p.Y65Ffs*50 in the affected brothers. Quantitative RT-PCR analysis showed markedly reduced AP4M1 mRNA levels suggesting partial non-sense mediated mRNA decay. Several clinical and MRI features were consistent with AP-4 complex deficiency. However, in contrast to previously reported cases with AP4M1 mutations our patients show an aggressive behavior and a relatively late onset of disease.CONCLUSION:This study shows an AP4M1 mutation associated with aggressive behavior in addition to mild dysmorphic features, intellectual disability, spastic paraparesis and reduced head circumference. Our findings expand the clinical spectrum associated with AP-4 complex deficiency and the study illustrates the importance of MRI and WES in the diagnosis of patients with CP and intellectual disability.
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| 4. |
- Khan, Tahir Naeem, et al.
(författare)
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Evidence for autosomal recessive inheritance in SPG3A caused by homozygosity for a novel ATL1 missense mutation
- 2014
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Ingår i: European Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1018-4813 .- 1476-5438. ; 22:10, s. 1180-1184
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Tidskriftsartikel (refereegranskat)abstract
- Hereditary spastic paraplegias (HSPs) comprise a heterogeneous group of disorders characterized by progressive spasticity and weakness of the lower limbs. Autosomal dominant and 'pure' forms of HSP account for similar to 80% of cases in Western societies of whom 10% carry atlastin-1 (ATL1) gene mutations. We report on a large consanguineous family segregating six members with early onset HSP. The pedigree was compatible with both autosomal dominant and autosomal recessive inheritance. Whole-exome sequencing and segregation analysis revealed a homozygous novel missense variant c.353G>A, p.(Arg118Gln) in ATL1 in all six affected family members. Seven heterozygous carriers, five females and two males, showed no clinical signs of HSP with the exception of sub-clinically reduced vibration sensation in one adult female. Our combined findings show that homozygosity for the ATL1 missense variant remains the only plausible cause of HSP, whereas heterozygous carriers are asymptomatic. This apparent autosomal recessive inheritance adds to the clinical complexity of spastic paraplegia 3A and calls for caution using directed genetic screening in HSP.
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| 5. |
- Khan, Tahir Naeem, et al.
(författare)
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Novel missense mutation in the RSPO4 gene in congenital hyponychia and evidence for a polymorphic initiation codon (p.M1l)
- 2012
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Ingår i: BMC Medical Genetics. - : Springer Science and Business Media LLC. - 1471-2350. ; 13, s. 120-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Anonychia/hyponychia congenita is a rare autosomal recessive developmental disorder characterized by the absence (anonychia) or hypoplasia (hyponuchia) of finger- and/or toenails frequently caused by mutations in the R-spondin 4 (RSPO4) gene. Methods: Three hypo/anonychia consanguineous Pakistani families were ascertained and genotyped using microsatellite markers spanning the RSPO4 locus on chromosome 20p13. Mutation screening of the RSPO4 gene was carried out by direct sequencing of the entire coding region and all intron-exon boundaries. Results: Mutations in the RSPO4 gene were identified in all families including a novel missense mutation c.178C>T (p.R60W) and two recurrent variants c.353G>A (p.C118Y) and c.3G>A (p.M1l). The c.3G>A variant was identified in unaffected family members and a control sample in a homozygous state. Conclusions: This study raises to 17 the number of known RSPO4 mutations and further expands the molecular repertoire causing hypo/anonychia. The c.353G>A emerges as a recurrent change with a possible founder effect in the Pakistani population. Our findings suggest that c.3G>A is not sufficient to cause the disorder and could be considered a polymorphism.
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| 6. |
- Li, Mingyu, et al.
(författare)
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Fabrication of Submicrometer InP Pillars by Colloidal Lithography and Dry Etching
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:9, s. II896-II899
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Tidskriftsartikel (refereegranskat)abstract
- A simple method for the fabrication of submicrometer InP pillars with large surface area coverage has been developed based on a combination of colloidal lithography and inductively coupled plasma (ICP) etching technique using Cl-2/H-2/CH4/Ar chemistry. Pillars with different sizes could be fabricated by using colloidal SiO2 particles with different sizes dispersed on the sample serving as masks. Pillars with lateral diameters as small as 60 nm and aspect ratios as high as 10: 1 have been obtained. The effects of etch parameters such as radio-frequency power, ICP power, and etching time on pillar fabrication are investigated. By a suitable choice of etch parameters and utilizing erosion of colloidal (mask) SiO2 particle during etching, the height of the pillars as well as their shape can be modified from nearly cylindrical to conical shapes. Such a control on the shape of the structures in addition to the large surface coverage could be useful for applications in photovoltaics and for the fabrication of photonic crystals. For instance, continuous grading of the refractive index can be obtained for surfaces covered with conical pillars, which can be used as antireflecting surfaces in solar cells or for light extraction in light emitting diodes.
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| 7. |
- Naureen, Shagufta, et al.
(författare)
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Carrier dynamics in InP nanopillar arrays fabricated by low-damage etching
- 2013
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 102:21, s. 212106-
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive characterization of the optical quality of InP nanopillars (NPs) fabricated by a top down approach using micro-photoluminescence (mu-PL), time-resolved PL, and cathodoluminescence (CL). A lattice matched InGaAs layer provided beneath the 1 mu m tall NPs functions as a "detector" in CL for monitoring carrier diffusion in InP NP. Carrier feeding to the InGaAs layer indicated by a double exponential PL decay is confirmed through CL mapping. Carrier lifetimes of over 1 ns and the appreciably long diffusion lengths (400-700 nm) in the InP NPs indicate very low surface damage making them attractive for optoelectronic applications.
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| 8. |
- Naureen, Shagufta, et al.
(författare)
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Generation of substrate-free III-V nanodisks from user-defined multilayer nanopillar arrays for integration on Si
- 2013
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 24:22, s. 225301-
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Tidskriftsartikel (refereegranskat)abstract
- High material quality InP-based multilayer nanopillar (NP) arrays are fabricated using a combination of self-assembly of silica particles for mask generation and dry etching. In particular, the NP arrays are made from user-defined epitaxial multilayer stacks with specific materials and layer thicknesses. An additional degree of flexibility in the structures is obtained by changing the lateral diameters of the NP multilayer stacks. Pre-defined NP arrays made from InGaAsP/InP and InGaAs/InP NPs are then used to generate substrate-free nanodisks of a chosen material from the stack by selective etching. A soft-stamping method is demonstrated to transfer the generated nanodisks with arbitrary densities onto Si. The transferred nanodisks retain their smooth surface morphologies and their designed geometrical dimensions. Both InP and InGaAsP nanodisks display excellent photoluminescence properties, with line-widths comparable to unprocessed reference epitaxial layers of similar composition. The multilayer NP arrays are potentially attractive for broad-band absorption in third-generation solar cells. The high optical quality, substrate-free InP and InGaAsP nanodisks on Si offer a new path to explore alternative ways to integrate III-V on Si by bonding nanodisks to Si. The method also has the advantage of re-usable III-V substrates for subsequent layer growth.
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| 9. |
- Naureen, Shagufta, et al.
(författare)
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High Optical Quality InP-Based Nanopillars Fabricated by a Top-Down Approach
- 2011
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 11:11, s. 4805-4811
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Tidskriftsartikel (refereegranskat)abstract
- Dense and uniform arrays of Top-based nanopillars were fabricated by dry etching using self-assembly of colloidal silica particles for masking. The pillars, both single and arrays, fabricated from epitaxially grown InP and InP/GaInAsP/InP quantum well structures :how excellent photoluminescence (PL) even at room temperature. The measured PL line widths are comparable to the as-grown wafer indicating high quality fabricated pillars. A stamping technique enables transfer with arbitrary densities of the nanopillars freed from the substrate by selectively etching a sacrificial InGaAs layer.
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| 10. |
- Naureen, Shagufta, et al.
(författare)
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Nanostructuring of InP by colloidal lithography and ICP etching for photovoltaic applications
- 2011
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Ingår i: Conference Proceedings - International Conference on Indium Phosphide and Related Materials. - 9783800733569
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a simple and cost effective method to fabricate InP nanopillars using silica particles as masks for etching InP. Oxygen plasma treatment of InP surfaces before dispersion of colloidal mask particles improved surface wettability significantly and helped in uniform coverage of the particles over large areas. Pillars with varied sizes were fabricated by dispersing colloidal SiO2 with different sizes on the sample and/or by reducing size of particles after dispersion. Nanopillars with different heights and shapes from near cylindrical to conical were obtained by varying etch process parameters and by progressive erosion of colloidal SiO 2 particle (mask). Pillars with aspect ratios in excess of 15:1 have been obtained. Investigations are also made on regular close packed hexagonal structures with wide area coverage. Size reduction of colloidal particles after dispersion is used to overcome the lag effect observed in the etching of close packed structures. The demonstrated nanostructuring method is attractive for producing photonic crystals and antireflecting surfaces in solar cells.
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