1,645 research outputs found
Raman spectra of GexAsySe1āxāy glasses
Various GeāAsāSe glasses spanning a mean coordination number (MCN) from 2.2 to 2.94 have been investigated using differential scanning calorimetry and Raman spectroscopy. The glass transition temperature Tg was found to increase with increasing MCN, except for those glasses located within the nanoscale phase-separated region of the phase diagram. The evolution of Raman features at wavenumbers from 150 to 350ācmā»Ā¹ exhibits two transitionlike features. Merging of the 225 and 250ācmā»Ā¹ modes at MCN=2.5 is a symbol of the extinction of SeāSe bonds. Additionally, the appearance of two modes at 280ā290 and 170ācmā»Ā¹ at MCN>2.7 come from the defect modes of ethanelike GeāSeā/ā. The increase in the scattering from these defects is an important factor leading to enhanced optical loss in the glasses with high MCN.This research was partly supported by the Australian
Research Council through its Centres of Excellence and Federation
Fellow Programs
Identification of presumed pathogenic KRT3 and KRT12 gene mutations associated with Meesmann corneal dystrophy.
PurposeTo report potentially pathogenic mutations in the keratin 3 (KRT3) and keratin 12 (KRT12) genes in two individuals with clinically diagnosed Meesmann corneal dystrophy (MECD).MethodsSlit-lamp examination was performed on the probands and available family members to identify characteristic features of MECD. After informed consent was obtained, saliva samples were obtained as a source of genomic DNA, and screening of KRT3 and KRT12 was performed. Potentially pathogenic variants were screened for in 200 control chromosomes. PolyPhen-2, SIFT, and PANTHER were used to predict the functional impact of identified variants. Short tandem repeat genotyping was performed to confirm paternity.ResultsSlit-lamp examination of the first proband demonstrated bilateral, diffusely distributed, clear epithelial microcysts, consistent with MECD. Screening of KRT3 revealed a heterozygous missense variant in exon 1, c.250C>T (p.(Arg84Trp)), which has a minor allele frequency of 0.0076 and was not identified in 200 control chromosomes. In silico analysis with PolyPhen-2 and PANTHER predicted the variant to be damaging to protein function; however, SIFT analysis predicted tolerance of the variant. The second proband demonstrated bilateral, diffusely distributed epithelial opacities that appeared gray-white on direct illumination and translucent on retroillumination. Neither parent demonstrated corneal opacities. Screening of KRT12 revealed a novel heterozygous insertion/deletion variant in exon 6, c.1288_1293delinsAGCCCT (p.(Arg430_Arg431delinsSerPro)). This variant was not present in either of the proband's parents or in 200 control chromosomes and was predicted to be damaging by PolyPhen-2, PANTHER, and SIFT. Haplotype analysis confirmed paternity of the second proband, indicating that the variant arose de novo.ConclusionsWe present a novel KRT12 mutation, representing the first de novo mutation and the first indel in KRT12 associated with MECD. In addition, we report a variant of uncertain significance in KRT3 in an individual with MECD. Although the potential pathogenicity of this variant is unknown, it is the first variant affecting the head domain of K3 to be reported in an individual with MECD and suggests that disease-causing variants associated with MECD may not be restricted to primary sequence alterations of either the helix-initiation or helix-termination motifs of K3 and K12
Investigation of the structure of GexAsySe1āxāy glasses by x-ray photoelectron spectroscopy
We have measured and analyzed x-ray photoelectron spectra of a series of GexAsySe1āxāyglasses. The valence band spectra show that a number of Se-rich structures exist in the samples. After decomposing Ge, As, and Se3dspectra into several doublets and assigning them to the different local bond structures, it was found that, while GeSeā/ā tetrahedral, AsSeā/ā pyramidal, and Se trimers decrease in their integrated areas, most defect bonds increase with increasing mean coordination number. Moreover, while the appearance of Se trimers is reasonable in Se-rich samples, they never vanish, even in Se-poor samples. A possible mechanism to form Se trimers in Se-poor samples is discussed.This research was supported by Australian Research
Council through its Centres of Excellence and Federation
Fellow Programs
High index contrast polysiloxane waveguides fabricated by dry etching
The authors demonstrate the production of low loss enhanced index contrast waveguides by reactive ion etching of IPGā¢ polysiloxane thin films. The use of a silica mask and CHFāāOāetch gas led to large etch selectivity between the silica and IPGā¢ of >20 and etch rates of >100nmāmin. This work indicates that compact optical circuits could be successfully fabricated for telecommunication applications using polysiloxane films.The support of the Australian Research Council through
its Linkage grant and Federation Fellow programs is gratefully
acknowledged as well as the financial support of RPO
Inc
Supercontinuum generation in dispersion engineered highly nonlinear (y=10/W/m) As2S3 chalcogenide planar waveguide
We demonstrate supercontinuum generation in a highly
nonlinear As2S3 chalcogenide planar waveguide which is dispersion
engineered to have anomalous dispersion at near-infrared wavelengths.
This waveguide is 60 mm long with a cross-section of 2 Ī¼m by 870 nm,
resulting in a nonlinear parameter of 10 /W/m and a dispersion of
+29 ps/nm/km. Using pulses with a width of 610 fs and peak power of
68 W, we generate supercontinuum with a 30 dB bandwidth of 750 nm, in
good agreement with theory
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