| 1. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 2. |
- Campbell, PJ, et al.
(författare)
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Pan-cancer analysis of whole genomes
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 578:7793, s. 82-
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Tidskriftsartikel (refereegranskat)abstract
- Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale1–3. Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4–5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter4; identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation5,6; analyses timings and patterns of tumour evolution7; describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity8,9; and evaluates a range of more-specialized features of cancer genomes8,10–18.
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| 3. |
- Carlevaro-Fita, J, et al.
(författare)
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Cancer LncRNA Census reveals evidence for deep functional conservation of long noncoding RNAs in tumorigenesis
- 2020
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Ingår i: Communications biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1, s. 56-
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Tidskriftsartikel (refereegranskat)abstract
- Long non-coding RNAs (lncRNAs) are a growing focus of cancer genomics studies, creating the need for a resource of lncRNAs with validated cancer roles. Furthermore, it remains debated whether mutated lncRNAs can drive tumorigenesis, and whether such functions could be conserved during evolution. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, we introduce the Cancer LncRNA Census (CLC), a compilation of 122 GENCODE lncRNAs with causal roles in cancer phenotypes. In contrast to existing databases, CLC requires strong functional or genetic evidence. CLC genes are enriched amongst driver genes predicted from somatic mutations, and display characteristic genomic features. Strikingly, CLC genes are enriched for driver mutations from unbiased, genome-wide transposon-mutagenesis screens in mice. We identified 10 tumour-causing mutations in orthologues of 8 lncRNAs, including LINC-PINT and NEAT1, but not MALAT1. Thus CLC represents a dataset of high-confidence cancer lncRNAs. Mutagenesis maps are a novel means for identifying deeply-conserved roles of lncRNAs in tumorigenesis.
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| 4. |
- Carlsson, JRA, et al.
(författare)
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A new silicon phosphide, Si12P5 : Formation conditions, structure, and properties
- 1997
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Ingår i: Journal of Vacuum Science and Technology A. - : American Vacuum Society. - 0734-2101. ; 15:2, s. 394-401
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Tidskriftsartikel (refereegranskat)abstract
- The formation conditions, structure, and properties of the recently discovered phosphide, Si12P5 (initially assigned Si7P3), have been studied using x-ray diffraction, high-resolution transmission electron microscopy, photospectrometry, and a four-point probe. The phosphide formed in amorphous Si-P alloy thin films with 30, 35 and 44 at. % P after annealing at 1000°C for 30 min. During annealing at 1100°C, the phosphide dissociated through P evaporation. The Si12P5 phase is proposed to have rhombohedral symmetry with a P31m space group and a C5W12 structure. The hexagonal lattice parameters measured were a = 6.16±0.05 Å and c = 13.17±0.01 Å. The optical band gap and the electrical resistivity of the phosphide were determined to be 1.55 eV and 5 mΩ cm, respectively. The Gibbs free energy diagram for the Si-P system was modified to include this new Si12P5 phase.
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| 5. |
- Edwards, NV, et al.
(författare)
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Real-time assessment of overlayer removal on 4H-SiC surfaces : Techniques and relevance to contact formation
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 338-3, s. 1033-1036
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Tidskriftsartikel (refereegranskat)abstract
- We applied real-time spectroscopic ellipsometric (SE) measurements to assess the removal of overlayer material from 4H-SiC Si- and C-face surfaces in order to investigate the final step of an otherwise standard RCA cleaning regimen commonly used to prepare SiC surfaces for contact formation. The selected treatments (buffered hydrofluoric acid (HF), concentrated HF, dilute HF and 5% HF in Methanol) removed 4 to 40 Angstrom of effective SiO2 overlayer thickness from these surfaces. We also found that the concentrated HF treatment yielded the best surface, i.e. the most abrupt bulk-to-ambient transition region.
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| 6. |
- Edwards, NV, et al.
(författare)
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Real-time assessment of selected surface preparation regimens for 4H-SiC surfaces using spectroscopic ellipsometry
- 2000
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Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 464:1, s. L703-L707
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Tidskriftsartikel (refereegranskat)abstract
- Spectroscopic ellipsometry (SE) was used to assess the removal of overlayer material from 4H-SiC (0001) and (0001) [Si- and C-face] surfaces in real time and, in particular, the critical final step of an otherwise standard RCA cleaning regimen commonly used to prepare SiC surfaces for contact formation. The treatments selected [buffered hydrofluoric acid (HF), concentrated HF, and dilute HF] removed 4-40 Angstrom of effective SiO2 overlayer thickness from these surfaces. The concentrated HF treatment yielded the best surface, i.e. that with the most abrupt transition region between bulk and surface and with the most oxide material removed. A fourth treatment regimen (sequential application of methanol, water, and 5% HF in methanol) was also developed for comparison with the full RCA clean. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 7. |
- Kassamakova, L, et al.
(författare)
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Al/Si ohmic contacts to p-type 4H-SiC for power devices
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 338-3, s. 1009-1012
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Tidskriftsartikel (refereegranskat)abstract
- The formation of Al/Si/p-4H SiC ohmic contacts at temperatures as low as 750 degreesC is reported in this paper. The dependence of electrical properties and contact morphology have been investigated as a function of the annealing regime in the interval 600-700 degreesC. The lowest contact resistivity of 3.8x10(-5) Omega .cm(2) was obtained at 700 degreesC annealing, however the most reproducible results were in the low 10(-4) Omega .cm(2) range. It has been established that the predominate current transport mechanism in the Al/Si/SiC contacts is thermionic-field emission. Atomic force microscopy showed that the addition of Si to the contact layer improves its morphology, and the pitting of annealed Al is not observed. The contacts developed are stable during ageing at 500 degreesC and at operating temperatures up to 450 degreesC. After the contacts testing with current density of 10(3) A/cm(2) at temperatures up to 450 degreesC, their contact resistivity decreases slightly.
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| 8. |
- Kassamakova, L, et al.
(författare)
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Temperature stable Pd ohmic contacts to p-type 4H-SiC formed at low temperatures
- 1999
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 46:3, s. 605-611
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Tidskriftsartikel (refereegranskat)abstract
- The formation of low resistivity Pd-based ohmic contacts to p-type 4H-SiC below 750 degrees C are reported herein, The electrical properties of the contacts were examined using I-V measurements and the transmission-line model (TLM) technique. Contact resistivity as a function of annealing was investigated over the temperature range of 600 degrees C-700 degrees C, The lowest contact resistivity (5.5 x 10(-5) Ohm cm(2)) was obtained after annealing at 700 degrees C for 5 min, Atomic force microscopy of the as-deposited Pd layer showed a root-mean square roughness of similar to 8 nm, while after annealing at 700 degrees C, agglomeration occurred, increasing the roughness to 111 nm, Auger electron spectroscopy depth profiles revealed that with annealing, interdiffusion had resulted in the formation of Pd-rich silicides. However, X-ray diffraction and Rutherford backscattering showed that the majority of the film was still (unreacted) Pd. The thermal stability and reliability of the Pd contacts were examined by aging and temperature dependence electrical tests, The contacts annealed at 700 OC were stable at prolonged heating at a constant temperature of 500 degrees C and they showed thermal stability in air at operating temperatures up to 450 degrees C, This stability was not found for contacts formed at lower temperatures of 600 degrees C or 650 degrees C.
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| 9. |
- McCaffrey, JP, et al.
(författare)
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Determination of the size, shape, and composition of indium-flushed self-assembled quantum dots by transmission electron microscopy
- 2000
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Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 88:5, s. 2272-2277
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Tidskriftsartikel (refereegranskat)abstract
- Single and multiple layers of self-assembled InAs quantum dots (QDs) produced by the indium-flush technique have been studied by transmission electron microscopy (TEM) in an effort to develop techniques to reproducibly grow QDs of uniform size and shape. To monitor the changes in QD dimensions, plan-view samples of capped single layers were studied as well as cross-sectional samples of QDs in multiple layers and stacks. The changes in the observed round- and square-shaped QD images under various plan-view TEM imaging conditions, as well as the contrast reversal in the center of QD images viewed in cross-section are modeled using the many-beam Bloch-wave approach, including strain. The sizes and shapes of the QDs are determined through the interpretation of the observed (primarily strain) contrast in plan-view and the observed (primarily atomic number) contrast in cross-sectional TEM. (C) 2000 American Institute of Physics. [S0021-8979(00)03217-5].
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| 10. |
- McCaffrey, JP, et al.
(författare)
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Size and shape engineering of vertically-stacked InAs quantum dots
- 1999
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Ingår i: Institute of Physics Conference Series. - 0951-3248 .- 2154-6630. ; :164, s. 107-110
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneous formation of nanostructures during epitaxial growth is one of the most successful techniques for in situ fabrication of quantum dots (QDs). We describe new size and shape engineering procedures for the growth of layers of stacked QDs, resulting in a significant narrowing of the size and shape distribution. Transmission electron microscopy (TEM) and photoluminescence (PL) indicate that the main effects of this size and shape engineering are to convert the quantum dots into a population of quantum disks with highly uniform height and diameter.
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| 11. |
- Mishra, A, et al.
(författare)
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Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
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Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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| 12. |
- Rheinbay, E, et al.
(författare)
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Analyses of non-coding somatic drivers in 2,658 cancer whole genomes
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 578:7793, s. 102-
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of drivers of cancer has traditionally focused on protein-coding genes1–4. Here we present analyses of driver point mutations and structural variants in non-coding regions across 2,658 genomes from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium5 of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). For point mutations, we developed a statistically rigorous strategy for combining significance levels from multiple methods of driver discovery that overcomes the limitations of individual methods. For structural variants, we present two methods of driver discovery, and identify regions that are significantly affected by recurrent breakpoints and recurrent somatic juxtapositions. Our analyses confirm previously reported drivers6,7, raise doubts about others and identify novel candidates, including point mutations in the 5′ region of TP53, in the 3′ untranslated regions of NFKBIZ and TOB1, focal deletions in BRD4 and rearrangements in the loci of AKR1C genes. We show that although point mutations and structural variants that drive cancer are less frequent in non-coding genes and regulatory sequences than in protein-coding genes, additional examples of these drivers will be found as more cancer genomes become available.
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| 13. |
- Robbie, K, et al.
(författare)
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Study of contact formation by high temperature deposition of Ni on SiC
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 338-3, s. 981-984
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Tidskriftsartikel (refereegranskat)abstract
- We report the observation, by scanning tunneling microscopy (STM), scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and atomic force microscopy (AFM), of island formation on SIC during high temperature deposition and annealing of thin Ni films. Ni films with a nominal thickness of 2.5 monolayers were sputter deposited onto H-2-etched single crystal 6H-SiC (0001) substrates heated to 600 degreesC in an ultrahigh vacuum STM system. After the substrates were annealed to 800-1000 degreesC, island formation was observed by STM. The islands were 0.1-0.5 mum in diameter, similar to 30 nm high, and separated by similar to2 mum from each other, with an exceptionally flat top with a peculiar 'stitched' surface structure. A second type of island, similar to1.5 mum in diameter, similar to 10 nm high, and separated by similar to 10 mum from each other, was observed by ex situ AFM and SEM. Microspot AES showed that the first islands are composed of Ni and C, while the second islands are composed of Ni, C, and Si. AES lineshape studies showed that the carbon in both types of islands is graphitically bound as opposed to the carbon in the substrate which is carbidically bound. From comparisons to literature, we believe that the first islands are a new type of graphite intercalation compound. An indexing of Ni on the top graphite sheets is presented for each anneal temperature.
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| 14. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 15. |
- Virojanadara, Chariya, et al.
(författare)
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Schottky barrier height studies of Au/4H-SiC(0001) using photoemission and synchrotron radiation
- 2002
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 31:12, s. 1353-1356
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Tidskriftsartikel (refereegranskat)abstract
- The Schottky barrier height (SBH) of Au on 4H-SiC(0001) has been studied using photoemission and synchrotron radiation. The Au was deposited in-situ on clean and well-ordered root3 X roots R30degrees reconstructed SiC surfaces prepared by in situ heating at similar to950degreesC. The SBH was determined from the shift observed in the Si 2p core level, in addition to the initial band bending determined for the clean surface. The results were compared with values obtained by electrical, capacitance-voltage (C-V), and current-voltage (I-V) characterization methods. A favorable comparison between the three independent, SBH determination methods was found.
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| 16. |
- Wahab, Qamar Ul, et al.
(författare)
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Designing, physical simulation and fabrication of high-voltage (3.85 kV) 4H-SiC Schottky rectifiers processed on hot-wall and chimney CVD films
- 2000
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Ingår i: Materials Science Forum, Vols. 338-342. ; , s. 1171-1174
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Konferensbidrag (refereegranskat)abstract
- Physical simulation, fabrication and characterization of high-voltage Ni/4H-SiC Schottky rectifiers are studied. We demonstrate a blocking voltage of 3.85 kV by utilizing a 43 mum thick low doped 4H-SiC epilayer in vertical hot-wall Chimney CVD reactor. A high breakdown voltage of 3.56 kV was achieved on a layer grown by conventional hot-wall CVD reactor. The reverse leakage current on CVD sample was as low as 5 x 10(-6) A cm(-2) at 3.5 kV just before the breakdown.
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| 17. |
- Wahab, Qamar Ul, et al.
(författare)
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Improvements in the electrical performance of high voltage 4H-SiC Schottky diodes by hydrogen annealing
- 2001
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Ingår i: Materials Science Forum, Vols. 353-356. ; , s. 691-694
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Konferensbidrag (refereegranskat)abstract
- A significant improvement in all the important parameters of the diodes were observed by annealing in H-2 at 300 degreesC. The forward current increased from 55 mA to 100 mA at a bias voltage of 2.5 V. The reverse leakage current measured at -500 V was reduced from 3.5 x 10(-9) to 4.8 x 10(-10) Amps for a 0.5 mm diameter diode. The average value of the barrier height increased by at least 0.2 eV, measured by Capacitance-Voltage and Current-Voltage technique indicating the increase of both static and effective barrier heights. The average value of ideality factor also improved and a best value of 1.06 was obtained for the hot-wall CVD grown samples after Hz annealing. Hydrogen atoms may passivate the dangling bends at the metal-semiconductor interface and thus by saturating the dangling bonds reduce the interface state density.
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| 18. |
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