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- Butler-Laporte, G, et al.
(författare)
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Exome-wide association study to identify rare variants influencing COVID-19 outcomes: Results from the Host Genetics Initiative
- 2022
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Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 18:11, s. e1010367-
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Tidskriftsartikel (refereegranskat)abstract
- Host genetics is a key determinant of COVID-19 outcomes. Previously, the COVID-19 Host Genetics Initiative genome-wide association study used common variants to identify multiple loci associated with COVID-19 outcomes. However, variants with the largest impact on COVID-19 outcomes are expected to be rare in the population. Hence, studying rare variants may provide additional insights into disease susceptibility and pathogenesis, thereby informing therapeutics development. Here, we combined whole-exome and whole-genome sequencing from 21 cohorts across 12 countries and performed rare variant exome-wide burden analyses for COVID-19 outcomes. In an analysis of 5,085 severe disease cases and 571,737 controls, we observed that carrying a rare deleterious variant in the SARS-CoV-2 sensor toll-like receptor TLR7 (on chromosome X) was associated with a 5.3-fold increase in severe disease (95% CI: 2.75–10.05, p = 5.41x10-7). This association was consistent across sexes. These results further support TLR7 as a genetic determinant of severe disease and suggest that larger studies on rare variants influencing COVID-19 outcomes could provide additional insights.
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- Alam, Syed Bahauddin, et al.
(författare)
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Small modular reactor core design for civil marine propulsion using micro-heterogeneous duplex fuel. Part I: Assembly-level analysis
- 2019
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Ingår i: Nuclear Engineering and Design. - : Elsevier BV. - 0029-5493 .- 1872-759X. ; 346, s. 157-175
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to de-carbonise commercial freight shipping, there is growing interest in the possibility of using nuclear propulsion systems. In this reactor physics study, we seek to design a soluble-boron-free (SBF) and low-enriched uranium (LEU) (<20% U-235 enrichment) civil nuclear marine propulsion small modular reactor (SMR) core that provides at least 15 effective full-power-years (EFPY) life at 333 MWth using 18% U-235 enriched micro-heterogeneous ThO2-UO2 duplex fuel and 15% U-235 enriched homogeneously mixed all-UO2 fuel. We use WIMS to develop subassembly designs and PANTHER to examine whole-core arrangements.The assembly-level behaviours of candidate burnable poison (BP) materials and control rods are investigated. We examine gadolinia (Gd2O3), erbia (Er2O3) and ZrB2 integral fuel burnable absorber (IFBA) as BPs. We arrive at a design with the candidate fuels loaded into 13 x 13 assemblies using IFBA pins for reactivity control. Taking advantage of self-shielding effects, this design maintains low and stable assembly reactivity with relatively little burnup penalty. Thorium-based duplex fuel offers better performance than all-UO2 fuel with all BP options considered. Duplex fuel has similar to 20% lower reactivity swing and, in consequence, lower initial reactivity than all-UO2 fuel. The lower initial reactivity and smaller reactivity swing make the task of reactivity control through BP design easier in the thorium-rich duplex core. For control rod design, we examine boron carbide (B4C), hafnium, and Ag-In-Cd alloy. All the candidate materials exhibit greater rod worth for the duplex design. For both fuels, B4C has the highest rod worth. In particular, one of the major objectives of this study is to offer/explore a thorium-based candidate alternative fuel platform for the proposed marine core. It is proven by literature reviews that the ability of the duplex fuel was never explored in the context of a single-batch, LEU, SBF, long-life SMR core. In this regard, the motivation of this paper is to observe the neutronic performance of the proposed duplex fuel with respect to the UO2 fuel and 'open the option' of designing the functional cores with both the duplex and UO2 fuel cores.
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| 8. |
- Alam, Syed Bahauddin, et al.
(författare)
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Small modular reactor core design for civil marine propulsion using micro-heterogeneous duplex fuel. Part II: whole-core analysis
- 2019
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Ingår i: Nuclear Engineering and Design. - : Elsevier BV. - 0029-5493 .- 1872-759X. ; 346, s. 176-191
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Tidskriftsartikel (refereegranskat)abstract
- Civil marine reactors face a unique set of design challenges. These include requirements for a small core size and long core lifetime, a 20% cap on fissile loading, and limitations on using soluble neutron absorbers. In this reactor physics study, we seek to design a core that meets these requirements over a 15 effective full-power-years (EFPY) life at 333 MWth using homogeneously mixed all-UO2 and micro-heterogeneous ThO2-UO2 duplex fuels. In a companion (Part I) paper, we found assembly designs using 15% and 18% U-235 for UO2 and duplex fuels, respectively, loaded into 13 x 13 pin arrays. High thickness (150 mu m) ZrB2 integral fuel burnable absorber (IFBA) pins and boron carbide (B4C) control rods are used for reactivity control. Taking advantage of self-shielding effects, these designs maintain low and stable assembly reactivity with little burnup penalty.In this paper (Part II), whole-core design analyses are performed for small modular reactor (SMR) to determine whether the core remains critical for at least 15 EFPY with a reactivity swing of less than 4000 pcm, subject to appropriate constraints. The main challenge is to keep the radial form factor below its limit (1.50). Burnable poison radial-zoning is examined in the quest for a suitable arrangement to control power peaking. Optimized assemblies are loaded into a 3D reactor model in PANTHER. The PANTHER results confirm that the fissile loadings of both fuels are well-designed for the target lifetime: at the end of the (similar to)15-year cycle, the cores are on the border of criticality. The duplex fuel core can achieve (similar to)4% longer core life, has a (similar to)3% lower initial reactivity and (similar to)30% lower reactivity swing over life than the final UO2 core design. The duplex core is therefore the more successful design, giving a core life of (similar to)16 years and a reactivity swing of less than 2500 pcm, while satisfying all the neutronic safety parameters. In particular, one of the major objectives of this study is to offer/explore a thorium-based candidate alternative fuel platform for the proposed marine core. It is proven by literature reviews that the ability of the duplex fuel was never explored in the context of a single-batch, LEU, SBF, long-life SMR core. In this regard, the motivation of this paper is to understand the underlying physics of the duplex fuel and 'open the option' of designing the functional cores with both the duplex and UO2 fuel cores.
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- Rehman, S., et al.
(författare)
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Experimental Investigation of Temperature Effect on Corrosive Sulfur Formation in Transformers
- 2017
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Ingår i: IEEE transactions on dielectrics and electrical insulation. - : IEEE. - 1070-9878 .- 1558-4135. ; 24:5, s. 3201-3206
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents experimental findings of the effect of temperature on corrosive sulfur formation in transformers. To conduct the experimental study, new transformer oil was randomly selected and heated at 40, 60, 80, 120, and 150 degrees C temperature for 72 hours each along with copper strips wrapped with insulation paper and immersed in oil in accordance with IEC-62535 standard test covered conductor deposition (CCD). The oil, copper strips, and the insulation paper samples were evaluated using gas chromatography-sulfur chemiluminescence detector (GC-SCD), X-ray fluorescence spectroscopy (XRF), inductively coupled plasma optical emission spectrometry (ICP), and scanning electron microscopy (SEM) tests after 72 hours exposure at each temperature. The values so obtained, were analyzed and effect of temperature on various parameters was studied individually and as well as collectively. It was found that temperature plays an important role on corrosive sulfur formation process inside the transformers and hence the temperature of the oil should be kept within the allowed operating ranges for avoiding unforeseen failures.
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