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  • 1
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 117, No. 5 ( 2020-02-04), p. 2560-2569
    Abstract: De novo mutations (DNMs), or mutations that appear in an individual despite not being seen in their parents, are an important source of genetic variation whose impact is relevant to studies of human evolution, genetics, and disease. Utilizing high-coverage whole-genome sequencing data as part of the Trans-Omics for Precision Medicine (TOPMed) Program, we called 93,325 single-nucleotide DNMs across 1,465 trios from an array of diverse human populations, and used them to directly estimate and analyze DNM counts, rates, and spectra. We find a significant positive correlation between local recombination rate and local DNM rate, and that DNM rate explains a substantial portion (8.98 to 34.92%, depending on the model) of the genome-wide variation in population-level genetic variation from 41K unrelated TOPMed samples. Genome-wide heterozygosity does correlate with DNM rate, but only explains 〈 1% of variation. While we are underpowered to see small differences, we do not find significant differences in DNM rate between individuals of European, African, and Latino ancestry, nor across ancestrally distinct segments within admixed individuals. However, we did find significantly fewer DNMs in Amish individuals, even when compared with other Europeans, and even after accounting for parental age and sequencing center. Specifically, we found significant reductions in the number of C→A and T→C mutations in the Amish, which seem to underpin their overall reduction in DNMs. Finally, we calculated near-zero estimates of narrow sense heritability ( h 2 ), which suggest that variation in DNM rate is significantly shaped by nonadditive genetic effects and the environment.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
    RVK:
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2020
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    American Physical Society (APS) ; 1990
    In:  Physical Review B Vol. 41, No. 3 ( 1990-1-15), p. 1645-1656
    In: Physical Review B, American Physical Society (APS), Vol. 41, No. 3 ( 1990-1-15), p. 1645-1656
    Type of Medium: Online Resource
    ISSN: 0163-1829 , 1095-3795
    RVK:
    Language: English
    Publisher: American Physical Society (APS)
    Publication Date: 1990
    detail.hit.zdb_id: 2844160-6
    detail.hit.zdb_id: 209770-9
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  • 3
    In: Journal of Applied Physics, AIP Publishing, Vol. 105, No. 6 ( 2009-03-15)
    Abstract: Thin films of the phase change material Ge–Sb with Ge concentrations between 7.3 and 81.1 at. % were deposited by cosputtering from elemental targets. Their crystallization behavior was studied using time-resolved x-ray diffraction, Auger electron spectroscopy, differential scanning calorimetry, x-ray reflectivity, profilometry, optical reflectivity, and resistivity versus temperature measurements. It was found that the crystallization temperature increases with Ge content. Calculations of the glass transition temperature (which is a lower limit for the crystallization temperature Tx) also show an increase with Ge concentration closely tracking the measured values of Tx. For low Ge content samples, Sb x-ray diffraction peaks occurred during a heating ramp at lower temperature than Ge diffraction peaks. The appearance of Ge peaks is related to Ge precipitation and agglomeration. For Ge concentrations of 59.3 at. % and higher, Sb and Ge peaks occurred at the same temperature. Upon crystallization, film mass density and optical reflectivity increase as well as electrical contrast (ratio of resistivity in amorphous phase to crystalline phase) all showed a maximum for the eutectic alloy (14.5 at. % Ge). For the alloy with 59.3 at. % Ge there was very little change in any of these parameters, while the alloy with 81.1 at. % Ge behaved opposite to a typical phase change alloy and showed reduced mass density and reflectivity and increased resistivity.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2009
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    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 4
    Online Resource
    Online Resource
    AIP Publishing ; 2014
    In:  Journal of Applied Physics Vol. 115, No. 9 ( 2014-03-07)
    In: Journal of Applied Physics, AIP Publishing, Vol. 115, No. 9 ( 2014-03-07)
    Abstract: GeTe is a well-know prototypical phase change material, while pure Sb is described as a material with strong resonant bonding properties which are indicative of a fast switching phase change material. We have studied the crystallization times and crystallization temperatures of phase-change materials along the GeTe-Sb pseudobinary line with compositions Ge1SbxTe1. It was observed that alloys with x ≈ 1–2 show the highest crystallization temperature and resistance in the crystalline phase (indicative of low reset current) but also the slowest crystallization speed. As many phase change materials, Ge1SbxTe1 materials also suffer from conflicting requirements between speed, thermal stability of the amorphous phase, and low reset current. The Ge-Sb-Te phase-change material compositions must be carefully designed to optimize device performance for a specific application. Ge1Sb6Te1 material is a promising candidate for storage-class memory with fast speed and a crystallization temperature that is substantially higher than Ge2Sb2Te5 thus promises good data retention.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2014
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 5
    In: Journal of Applied Physics, AIP Publishing, Vol. 104, No. 7 ( 2008-10-01)
    Abstract: Crystallization behavior of scalable phase change materials can be studied on nanoscale structures. In this paper, high density ordered phase change nanodot arrays were fabricated using the lift-off technique on a self-assembled diblock copolymer template, polystyrene-poly(methyl-methacrylate). The size of the nanodots was less than 15 nm in diameter with 40 nm spacing. This method is quite flexible regarding the patterned materials and can be used on different substrates. The crystallization behavior of small scale phase change nanodot arrays was studied using time-resolved x-ray diffraction, which showed the phase transition for different materials such as Ge15Sb85, Ge2Sb2Te5, and Ag and In doped Sb2Te. The transition temperatures of these nanodot samples were also compared with their corresponding blanket thin films, and it was found that the nanodots had higher crystallization temperatures and crystallized over a broader temperature range.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 6
    In: Journal of Applied Physics, AIP Publishing, Vol. 102, No. 9 ( 2007-11-01)
    Abstract: We have used time-resolved x-ray diffraction to study the amorphous-crystalline phase transition in 20–80nm particles of the phase change materials Ge2Sb2Te5, nitrogen-doped Ge2Sb2Te5, Ge15Sb85, Sb2Te, and Sb2Te doped with Ag and In. We find that all samples undergo the phase transition with crystallization temperatures close to those of similarly prepared blanket films of the same materials with the exception of Sb2Te that shows the transition at a temperature that is about 40°C higher than that of blanket films. Some of the nanoparticles show a difference in crystallographic texture compared to thick films. Large area arrays of these nanoparticles were fabricated using electron-beam lithography, keeping the sample temperatures well below the crystallization temperatures so as to produce particles that were entirely in the amorphous phase. The observation that particles with diameters as small as 20nm can still undergo this phase transition indicates that phase change solid-state memory technology should scale to these dimensions.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2007
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    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 7
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2009
    In:  MRS Proceedings Vol. 1156 ( 2009)
    In: MRS Proceedings, Springer Science and Business Media LLC, Vol. 1156 ( 2009)
    Abstract: Glancing-incidence X-ray diffraction (GIXRD) has been applied to the investigation of depth-dependent stress distributions within electroplated Cu films due to overlying capping layers. 0.65 μm thick Cu films plated on conventional barrier and seed layers received a CVD SiC x N y H z cap, an electrolessly-deposited CoWP layer, or a CoWP layer followed by a SiC x N y H z cap. GIXRD and conventional X-ray diffraction measurements revealed that strain gradients were created in Cu films possessing a SiC x N y H z cap, where a greater in-plane tensile stress was generated near the film / cap interface. The constraint imposed by the SiC x N y H z layer during cooling from the cap deposition temperature led to an increase in the in-plane stress of approximately 180 MPa from the value measured in the bulk Cu. However, Cu films possessing a CoWP cap without a SiC x N y H z layer did not exhibit depth-dependent stress distributions. Because the CoWP capping deposition temperature was much lower than that employed in SiC x N y H z deposition, the Cu experienced elastic deformation during the capping process. Cross-sectional transmission electron microscopy indicated that the top surface of the Cu films exhibited extrusions near grain boundaries for the samples undergoing the thermal excursion during SiC x N y H z deposition. The conformal nature of these caps confirmed that the morphological changes of the Cu film surface occurred prior to capping and are a consequence of the thermal excursions associated with cap deposition.
    Type of Medium: Online Resource
    ISSN: 0272-9172 , 1946-4274
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2009
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  • 8
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2010
    In:  MRS Proceedings Vol. 1251 ( 2010)
    In: MRS Proceedings, Springer Science and Business Media LLC, Vol. 1251 ( 2010)
    Abstract: Germanium ion implantation at an energy of 30 keV was used as a different method to re-amorphize thin films of crystalline phase change material Ge 2 Sb 2 Te 5 (GST). It was found that rather low doses of 5×10 13 cm -2 were sufficient to re-amorphize GST. Amorphization was determined by X-ray diffraction (XRD) as well as reflectivity measurements. Re-crystallization characteristics of ion-implantation-amorphized samples was studied using time-resolved XRD. It showed that samples re-crystallize at an increased crystallization temperature with increasing dose compared to as-deposited material. A static laser tester was applied to measure the crystallization times of material that was (1) as–deposited amorphous; (2) crystallized by annealing and re-amorphized by melt-quenching using a laser pulse; and (3) crystallized by annealing and re-amorphized by ion implantation. It was found that as-deposited amorphous and high-dose ion implanted samples had longer crystallization times while melt-quenched amorphous and low-dose ion implanted samples had shorter crystallization times.
    Type of Medium: Online Resource
    ISSN: 0272-9172 , 1946-4274
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2010
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  • 9
    Online Resource
    Online Resource
    American Chemical Society (ACS) ; 2013
    In:  Chemistry of Materials Vol. 25, No. 15 ( 2013-08-13), p. 3172-3179
    In: Chemistry of Materials, American Chemical Society (ACS), Vol. 25, No. 15 ( 2013-08-13), p. 3172-3179
    Type of Medium: Online Resource
    ISSN: 0897-4756 , 1520-5002
    Language: English
    Publisher: American Chemical Society (ACS)
    Publication Date: 2013
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  • 10
    Online Resource
    Online Resource
    AIP Publishing ; 2009
    In:  Applied Physics Letters Vol. 94, No. 18 ( 2009-05-04)
    In: Applied Physics Letters, AIP Publishing, Vol. 94, No. 18 ( 2009-05-04)
    Abstract: The crystallization temperature Tx of the phase change material Ge–Sb as a function of film thickness and cladding material was measured using time-resolved x-ray diffraction. For films & gt;5 nm, a weak influence of the cladding material on Tx was found (increase for Si, SiN, Pt, SiC, and TiN and decrease for Al and W). For very thin films, however, Tx differed up to 200 °C. Doping of Ge–Sb with these materials led to an increase in Tx in all cases, up to a maximum of 180 °C for SiN. Such a large influence of interfaces and doping on Tx is of great technological importance.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
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    Language: English
    Publisher: AIP Publishing
    Publication Date: 2009
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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