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Background: Biallelic variants in POLR1C are associated with POLR3-related leukodystrophy (POLR3-HLD), or 4H leukodystrophy (Hypomyelination, Hypodontia, Hypogonadotropic Hypogonadism), and Treacher Collins syndrome (TCS). The clinical spectrum of POLR3-HLD caused by variants in this gene has not been described. Methods: A cross-sectional observational study involving 25 centers worldwide was conducted between 2016 and 2018. The clinical, radiologic and molecular features of 23 unreported and previously reported cases of POLR3-HLD caused by POLR1C variants were reviewed. Results: Most participants presented between birth and age 6 years with motor difficulties. Neurological deterioration was seen during childhood, suggesting a more severe phenotype than previously described. The dental, ocular and endocrine features often seen in POLR3-HLD were not invariably present. Five patients (22%) had a combination of hypomyelinating leukodystrophy and abnormal craniofacial development, including one individual with clear TCS features. Several cases did not exhibit all the typical radiologic characteristics of POLR3-HLD. A total of 29 different pathogenic variants in POLR1C were identified, including 13 new disease-causing variants. Conclusions: Based on the largest cohort of patients to date, these results suggest novel characteristics of POLR1C-related disorder, with a spectrum of clinical involvement characterized by hypomyelinating leukodystrophy with or without abnormal craniofacial development reminiscent of TCS.
Background: Cerebellar atrophy is characterized by loss of cerebellar tissue, with evidence on brain imaging of enlarged interfolial spaces compared to the foliae. Genetic ataxias associated with cerebellar atrophy are a heterogeneous group of disorders. We investigated the prevalence in Canada and the diagnostic yield of whole exome sequencing (WES) for this group of conditions. Methods: Between 2011 and 2017, WES was performed in 91 participants with cerebellar atrophy as part of one of two national research programs, Finding of Rare Genetic Disease Genes (FORGE) or Enhanced Care for Rare Genetic Diseases in Canada (Care4Rare). Results: A genetic diagnosis was established in 58% of cases (53/91). Pathogenic variants were found in 24 known genes, providing a diagnosis for 46/53 participants (87%), and in four novel genes, accounting for 7/53 cases (13%). 38/91 cases (42%) remained unsolved. The most common diagnoses were channelopathies in 12/53 patients (23%) and mitochondrial disorders in 9/53 (17%). Inheritance was autosomal recessive in the majority of cases. Additional clinical findings provided useful clues to some of the diagnoses. Conclusions: This is the first report on the prevalence of genetic ataxias associated with cerebellar atrophy in Canada, and the utility of WES for this group of conditions.
We report on the results of CCD photometric observations of the open cluster NGC 2539. Eight new variable stars have been found in the observed field of this cluster. However, no γ Doradus-type variability was found among the member stars.
An acute gastroenteritis (AGE) outbreak was reported in May 2013 in Gyeonggi Province, South Korea. Eight students who had eaten breakfast on 21 May 2013 at a high-school restaurant exhibited AGE symptoms. Our case-control study showed that a strong association was observed between AGE symptoms and fermented oyster consumption. Virological studies also indicated that noroviruses (NoVs) were detected from both clinical samples and fermented oyster samples, and multiple different genotypes (genogroups GII.4, GII.11 and GII.14) of NoVs were present in both samples. The nucleotide sequence similarity between the strains found in the clinical samples and those in the fermented oysters was more than 99·5%. Therefore, to prevent further outbreaks, proper management of raw oysters is necessary and the food industry should be aware of the risk of viral gastroenteritis posed by fermented oysters contaminated with NoVs.
Copper films on Si(100) were prepared by partially ionized beam at 0 kV and 3 kV acceleration voltages in order to investigate effects of ion energy on electrical property with thickness. X-ray diffraction(XRD) pattern analysis was used to investigate crystallinity of the copper films, microstructure by Scanning electron microscope(SEM) and surface roughness by atomic force microscopy(AFM). The crystallinity of the copper films grown at the 3 kV was more (111) textured than that at the 0 kW. The copper films grown at the both condiitions had nearly same grain size below a thickness of 1000 Å. The 1800 Å Cu film grown at the 3 kV was 3 times rough than that at the 0 kV. The resistivity of copper films increased due to surface and grain boundary scattering, and the change of resistivity was discussed in terms of surface roughness, grain size and film density assisted by average depositing energy.
Undoped tin oxide films were grown on Si substrates by a reactive ion-assisted deposition technique in which oxygen ions were irradiated on depositing Sn particles. In order to investigate the oxidation from SnO to SnO2, the effects of initial oxygen contents and heat treatment on the final crystalline structure of tin oxide films were thoroughly examined. Oxygen to Sn metal ratio (No/Nsn) of as-deposited films were controlled from 1.1 to 1.9 by varying the relative arrival ratio (F) of oxygen ion to Sn particle from 0.025 to 0.1. Heat treatment was carried out in two different ways; one was post vacuum-annealing at 400 ∼ 600°C and the other was in-situ annealing 400 ∼ 500°C. Crystalline structure of as-deposited tin oxide films at room temperature was amorphous. After post-annealing at 400°C, only SnO phase was found below No/Nsn= 1.6 in x-ray diffraction and crystalline structure of the films comprising higher oxygen contents still appeared to be amorphous. Even though the films still showed SnO phase until Γ50 after 500°C post-annealing, however, mixed structures of SnO, SnO2, and intermediate Sn2O3/Sn3O4 were observed for the films Γ75 and Γ100 with higher oxygen contents. At 600°C annealing, perfect SnO2 phase was attained for the films having No/Nsn=1.9. On the other hand, pure polycrystalline SnO2 films could be obtained by in-situ annealing at low temperature. The values of No/Nsn and the chemical shifts with the variation of oxidation were carefully determined by the comparison of Sn MNN and O KLL Auger transitions. Surface microstructure of deposited films was also analyzed using a scanning electron microscopy (SEM) and an atomic force microscope (AFM).
We have investigated the reliability of the inverted-staggered etch stopper structure oxide-based TFTs under negative gate bias stress combined with 400 nm wavelength light illumination and the relationship between the carrier concentration at the channel and the extent of Vth shift. It was found that the photo-induced holes cause the severe Vth degradation at the beginning of stress and the hole trapping rate of a single hole is not altered with the increase of the hole concentration. In oxide-based TFTs, the hole concentration at the channel is the determinant factor of the reliability.
Photo luminescence (PL) signal from the aluminum nitride (AlN) films, excited by near UV (363.8 nm) laser has been measured at the room temperature. The AlN films are deposited by radio frequency (RF) sputtering of aluminum in argon-nitrogen-hydrogen gas mixture. Positions of the PL peaks maximums are influenced by the AlN preparation regimes. The analysis of the PL data is based on the results of the structural studies and electron spectrum investigations.
We studied on the effect of a deposition condition of precursor a-Si thin films on the shape and micro-structure of MILC. The a-Si thin films were prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD) with silane and hydrogen as a source gas and the deposition temperature was varied from 100 to 400∼. The a-Si films deposited at a lower temperature showed a tendency to (111) crystals and leaving some a-Si residues in MILC region, while those with higher deposition temperature tended to be crystallized to (110). These differences were explained in terms of original hydrogen content and following structural changes by the dehydrogenation during annealing.
Second order non-linear optical (NLO) polymers have been the focus of intense research effort in recent years . This effort is justified by the potential value of these materials in a range of attractive optical signal processing applications with lower device costs and enhanced device performance.
Plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) has been successfully employed for the deposition of (100) oriented barium strontium titanate (BST) thin films on a variety of substrate and electrode materials. The incorporation of O2 plasma, which was used as oxidation reactant, has helped to reduce the required temperature for deposition of high-quality STO and BST thin films. This low temperature processing may make it possible to integrate BST on Si and GaAs. BST films with low leakage current densities of about 10−7 A/cm2 at 2-volt (about 105 V/cm) operation were obtained from PE-MOCVD processing. Moreover, the BST results of capacitance-temperature (C-T) measurements show that most of the PE-MOCVD BST films have Curie temperatures of about 30–35°C and a peak dielectric constant of 600–800 at zero bias voltage, The sharp transition in the C-T data indicates that the BST films may have a high induced pyroelectric coefficient at room temperature, which is highly desirable for uncooled IR imaging arrays. The x-ray diffraction and Rutherford backscattering spectrometry results show that the BST film composition reproducibility was well controlled at around Ba0.75Sr0.25TiO3 with a 4% variation. Device quality BST thin films with the thickness of 1000–2000 Å were produced. These results indicate that PE-MOCVD has high potential to be further developed and promoted as a production deposition technique providing high permittivity dielectric thin films for microelectronics and IR sensor industries.
Several segmented, rigid-rod polyimides have been prepared that are soluble in organic solvents in their fully imidized form. The polymers were prepared from commercial dianhydrides and 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFMB). Their intrinsic viscosities ranged from 1.0 to 4.9 dL/g. Tough, colorless films could be cast from m-cresol solutions at 100°C. The polymers had glass transition temperatures (Tgs) above 275°C and displayed outstanding thermal and thermo-oxidative stability. Fibers were prepared from the 3,3′,4,4′-tetracarboxybiphenyl dianhydride (BPDA) based polymers that had moduli of 130 GPa and tensile strengths of 3.2 GPa. The thermal expansion coefficients and dielectric constants of thin films (20–25 μm) of the polymers were as low as −2.40×10−6 and 2.5, respectively.
In situ Zn-doped InP layers are grown by low pressure metalorganic chemical vapor deposition at 620°C. Hole concentration increases with dopant flow rate, but reaches a saturated hole concentration of approximately 1.5 × 1018/cm3. Differently from the Zn-diffused InP case, photoluminescence (PL) of the in situ Zn doped InP shows band edge peak, e/D-A peak and distant D-A peak up to the hole concentration of 7.6 × 1017/cm3. These results can be explained by less generation of interstitial Zn atoms during in situ doping. PL characteristics of the in situ Zn-doped InP at the saturated hole concentration is extensively studied to explain its compensation mechanism. Two new deep bands, presumably responsible for the hole saturation behavior, are observed for the first time.
Tight-binding molecular dynamics calculations reveal a new mechanism for hydrogen diffusion in hydrogenated amorphous silicon. Hydrogen diffuses through the network by successively bonding with nearby silicon and breaking their Si-Si bonds. The diffusing hydrogen carries with it a newly created dangling bond. These intermediate transporting states are densely populated in the network and have lower energies than H at the center of stretched Si-Si bonds.
Three different types of carbon nanotubes being considered for bio-recognition experiments were studied using resonance Raman spectroscopy. Raman spectroscopy, taken using several laser excitation energies, has been shown to provide an effective characterization tool for these carbon nanotubes. The technique yields structural information that both complements and corroborates structural information obtained using electron microscopy techniques, such as TEM, SEM, and AFM.
Zinc composition variation and gross structural defects including grain and tilt boundaries, twins, and mechanical cracks in high pressure Bridgman Cd1−xZnxTe are characterized and correlated to various detector-related responses. Triple axis x-ray diffraction, double crystal x-ray topography, infrared microscopy, and etch pit density measurements are used to reveal and quantify the spatial distribution and the nature of the structural defects. Mechanical cracks in the material are found to act as conductive “shorting paths”, indicated by excessive leakage currents and reduced charge (electron) collection measured along these cracks. Reduced charge collection is also obtained across grain boundaries and in regions with poor crystallinity, indicating that they serve as carrier recombination sites. Finally, the effects of the zinc composition variation on the measured leakage current and the amount of electrons collected are found to be masked by gross structural defects. These characterization techniques provide a wealth of information which can be used not only to study the relationship between the structural and device properties of CdZnTe but also to screen production material for subsequent device fabrication.
We have characterized ZnSe material grown by chemical vapor transport in iodine using triple-axis X-ray diffraction (TAD), photo-induced current transient spectroscopy (PICTS), photoluminescence (PL), current-voltage measurements and gamma-ray spectroscopy. The material was found to have inadequate carrier transport for nuclear spectrometer use, but there was a discernible difference in performance between crystals which could be correlated with crystallinity as determined by the TAD rocking curves.
Amorphous hydrogenated silicon carbide (a-Sil-xCx:H) thin films have been deposited by the electron cyclotron resonance chemical vapor deposition (ECR-CVD) technique at different microwave powers from 100W to 1000W. The films were characterized in terms of their optical absorption and photoluminescence (PL). Their optical band gap E04 ranged from 3.06eV to 3.54eV and when excited at 363.8nm from an Ar+ ion laser, the PL peak emission energy Epl, was found to range from 2.44eV to 2.79eV, corresponding to green to blue emission. The effects of excitation energy Eex, on Epl, and FWHM of the PL spectra were also investigated. A linear relation between the FWHM and Urbach tail width E0was noted, suggesting that the PL bandwidth is mainly contributed by static disorder. The blue emission observed in these a-S1-x-Cx:H films is promising for their applications in large area flat panel displays.
Cadmium Zinc Telluride (CZT) shows great promise as a semiconductor radiation detector material. CZT possesses advantageous material properties over other radiation detector materials in use today, such as a high intrinsic resistivity and a high cross-section for x and γ-rays. However, presently available CZT is not without limitations. The hole transport properties severely limit the performance of these detectors, and the yield of material possessing adequate electron transport properties is currently much lower than desired. The result of these material deficiencies is a lack of inexpensive CZT crystals of large volume for several radiation detector applications. One approach to help alleviate this problem is to measure the spatial distribution (or map) the electrical properties of large area CZT wafers prior to device fabrication. This mapping can accomplish two goals: identify regions of the wafers suitable for detector fabrication and correlate the distribution of crystalline defects with the detector performance. The results of this characterization can then be used by the crystal manufacturers to optimize their growth processes. In this work, we discuss the design and performance of apparatus for measuring the electrical characteristics of entire CZT wafers (up to 10 cm × 10 cm). The data acquisition and manipulation will be discussed and some typical data will be presented.
Zinc composition variation and gross structural defects including grain and tilt boundaries, twins, and mechanical cracks in high pressure Bridgman Cd1−xZnxTe are characterized and correlated to various detector-related responses. Triple axis x-ray diffraction, double crystal x-ray topography, infrared microscopy, and etch pit density measurements are used to reveal and quantify the spatial distribution and the nature of the structural defects. Mechanical cracks in the material are found to act as conductive ‘shorting paths’, indicated by excessive leakage currents and reduced charge (electron) collection measured along these cracks. Reduced charge collection is also obtained across grain boundaries and in regions with poor crystallinity, indicating that they serve as carrier recombination sites. Finally, the effects of the zinc composition variation on the measured leakage current and the amount of electrons collected are found to be masked by gross structural defects. These characterization techniques provide a wealth of information which can be used not only to study the relationship between the structural and device properties of CdZnTe but also to screen production material for subsequent device fabrication.