| 1. |
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| 2. |
- Heid, Iris M, et al.
(författare)
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Meta-analysis identifies 13 new loci associated with waist-hip ratio and reveals sexual dimorphism in the genetic basis of fat distribution
- 2010
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 42:11, s. 949-960
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Tidskriftsartikel (refereegranskat)abstract
- Waist-hip ratio (WHR) is a measure of body fat distribution and a predictor of metabolic consequences independent of overall adiposity. WHR is heritable, but few genetic variants influencing this trait have been identified. We conducted a meta-analysis of 32 genome-wide association studies for WHR adjusted for body mass index (comprising up to 77,167 participants), following up 16 loci in an additional 29 studies (comprising up to 113,636 subjects). We identified 13 new loci in or near RSPO3, VEGFA, TBX15-WARS2, NFE2L3, GRB14, DNM3-PIGC, ITPR2-SSPN, LY86, HOXC13, ADAMTS9, ZNRF3-KREMEN1, NISCH-STAB1 and CPEB4 (P = 1.9 × 10⁻⁹ to P = 1.8 × 10⁻⁴⁰) and the known signal at LYPLAL1. Seven of these loci exhibited marked sexual dimorphism, all with a stronger effect on WHR in women than men (P for sex difference = 1.9 × 10⁻³ to P = 1.2 × 10⁻¹³). These findings provide evidence for multiple loci that modulate body fat distribution independent of overall adiposity and reveal strong gene-by-sex interactions.
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| 3. |
- Speliotes, Elizabeth K., et al.
(författare)
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Association analyses of 249,796 individuals reveal 18 new loci associated with body mass index
- 2010
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 42:11, s. 937-948
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is globally prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined associations between body mass index and ~2.8 million SNPs in up to 123,865 individuals with targeted follow up of 42 SNPs in up to 125,931 additional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci associated with body mass index (P < 5 × 10−8), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly associated loci may provide new insights into human body weight regulation.
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| 4. |
- Berndt, Sonja I., et al.
(författare)
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Genome-wide meta-analysis identifies 11 new loci for anthropometric traits and provides insights into genetic architecture
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 45:5, s. 501-U69
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Tidskriftsartikel (refereegranskat)abstract
- Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.
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| 5. |
- Kilpeläinen, Tuomas O, et al.
(författare)
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Genome-wide meta-analysis uncovers novel loci influencing circulating leptin levels
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Leptin is an adipocyte-secreted hormone, the circulating levels of which correlate closely with overall adiposity. Although rare mutations in the leptin (LEP) gene are well known to cause leptin deficiency and severe obesity, no common loci regulating circulating leptin levels have been uncovered. Therefore, we performed a genome-wide association study (GWAS) of circulating leptin levels from 32,161 individuals and followed up loci reaching P<10(-6) in 19,979 additional individuals. We identify five loci robustly associated (P<5 × 10(-8)) with leptin levels in/near LEP, SLC32A1, GCKR, CCNL1 and FTO. Although the association of the FTO obesity locus with leptin levels is abolished by adjustment for BMI, associations of the four other loci are independent of adiposity. The GCKR locus was found associated with multiple metabolic traits in previous GWAS and the CCNL1 locus with birth weight. Knockdown experiments in mouse adipose tissue explants show convincing evidence for adipogenin, a regulator of adipocyte differentiation, as the novel causal gene in the SLC32A1 locus influencing leptin levels. Our findings provide novel insights into the regulation of leptin production by adipose tissue and open new avenues for examining the influence of variation in leptin levels on adiposity and metabolic health.
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| 6. |
- Erzurumluoglu, A. Mesut, et al.
(författare)
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Meta-analysis of up to 622,409 individuals identifies 40 novel smoking behaviour associated genetic loci
- 2020
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Ingår i: Molecular Psychiatry. - : Nature Publishing Group. - 1359-4184 .- 1476-5578. ; 25:10, s. 2392-2409
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Tidskriftsartikel (refereegranskat)abstract
- Smoking is a major heritable and modifiable risk factor for many diseases, including cancer, common respiratory disorders and cardiovascular diseases. Fourteen genetic loci have previously been associated with smoking behaviour-related traits. We tested up to 235,116 single nucleotide variants (SNVs) on the exome-array for association with smoking initiation, cigarettes per day, pack-years, and smoking cessation in a fixed effects meta-analysis of up to 61 studies (up to 346,813 participants). In a subset of 112,811 participants, a further one million SNVs were also genotyped and tested for association with the four smoking behaviour traits. SNV-trait associations with P < 5 × 10-8 in either analysis were taken forward for replication in up to 275,596 independent participants from UK Biobank. Lastly, a meta-analysis of the discovery and replication studies was performed. Sixteen SNVs were associated with at least one of the smoking behaviour traits (P < 5 × 10-8) in the discovery samples. Ten novel SNVs, including rs12616219 near TMEM182, were followed-up and five of them (rs462779 in REV3L, rs12780116 in CNNM2, rs1190736 in GPR101, rs11539157 in PJA1, and rs12616219 near TMEM182) replicated at a Bonferroni significance threshold (P < 4.5 × 10-3) with consistent direction of effect. A further 35 SNVs were associated with smoking behaviour traits in the discovery plus replication meta-analysis (up to 622,409 participants) including a rare SNV, rs150493199, in CCDC141 and two low-frequency SNVs in CEP350 and HDGFRP2. Functional follow-up implied that decreased expression of REV3L may lower the probability of smoking initiation. The novel loci will facilitate understanding the genetic aetiology of smoking behaviour and may lead to the identification of potential drug targets for smoking prevention and/or cessation.
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| 7. |
- Sarwar, Nadeem, et al.
(författare)
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Interleukin-6 receptor pathways in coronary heart disease : a collaborative meta-analysis of 82 studies
- 2012
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Ingår i: The Lancet. - New York, NY, USA : Elsevier. - 0140-6736 .- 1474-547X. ; 379:9822, s. 1205-1213
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Tidskriftsartikel (refereegranskat)abstract
- Background: Persistent inflammation has been proposed to contribute to various stages in the pathogenesis of cardiovascular disease. Interleukin-6 receptor (IL6R) signalling propagates downstream inflammation cascades. To assess whether this pathway is causally relevant to coronary heart disease, we studied a functional genetic variant known to affect IL6R signalling. Methods: In a collaborative meta-analysis, we studied Asp358Ala (rs2228145) in IL6R in relation to a panel of conventional risk factors and inflammation biomarkers in 125 222 participants. We also compared the frequency of Asp358Ala in 51 441 patients with coronary heart disease and in 136 226 controls. To gain insight into possible mechanisms, we assessed Asp358Ala in relation to localised gene expression and to postlipopolysaccharide stimulation of interleukin 6. Findings: The minor allele frequency of Asp358Ala was 39%. Asp358Ala was not associated with lipid concentrations, blood pressure, adiposity, dysglycaemia, or smoking (p value for association per minor allele >= 0.04 for each). By contrast, for every copy of 358Ala inherited, mean concentration of IL6R increased by 34.3% (95% CI 30.4-38.2) and of interleukin 6 by 14.6% (10.7-18.4), and mean concentration of C-reactive protein was reduced by 7.5% (5.9-9.1) and of fibrinogen by 1.0% (0.7-1.3). For every copy of 358Ala inherited, risk of coronary heart disease was reduced by 3.4% (1.8-5.0). Asp358Ala was not related to IL6R mRNA levels or interleukin-6 production in monocytes. Interpretation: Large-scale human genetic and biomarker data are consistent with a causal association between IL6R-related pathways and coronary heart disease.
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| 8. |
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| 9. |
- Andersson, Peter, 1981-, et al.
(författare)
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Simulation of the response of a segmented High-Purity Germanium detector for gamma emission tomography of nuclear fuel
- 2020
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Ingår i: SN Applied Sciences. - : Springer. - 2523-3963 .- 2523-3971. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Irradiation testing of nuclear fuel is routinely performed in nuclear test reactors. For qualification and licensing of Accident Tolerant Fuels or Generation IV reactor fuels, an extensive increase in irradiation testing is foreseen in order to fill the gaps of existing validation data, both in normal operational conditions and in order to identify operational limits.Gamma Emission Tomography (GET) has been demonstrated as a viable technique for studies of the behavior of irradiated nuclear fuel, e.g. measurement of fission gas release and inspection of fuel behavior under Loss-Of-Coolant Accident conditions. In this work, the aim is to improve the technique of GET for irradiated nuclear fuel by developing a detector concept for an improved tomography system that allows for a higher spatial resolution and/or faster interrogation.We present the working principles of a novel concept for gamma emission tomography using a segmented High Purity Germanium (HPGe) detector. The performance of this concept was investigated using the Monte Carlo particle transport code MCNP. In particular, the data analysis of the proposed detector was evaluated, and the performance, in terms of full energy efficiency and localization failure rate, has been evaluated.We concluded that the segmented HPGe detector has an advantageous performance as compared to the traditional single-channel detector systems. Due to the scattering nature of gamma rays, a trade-off is presented between efficiency and cross-talk; however, the performance is nevertheless a substantial improvement over the currently used single-channel HPGe detector systems.
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| 10. |
- Atak, Haluk, et al.
(författare)
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The degradation of gamma-ray mass attenuation of UOX and MOX fuel with nuclear burnup
- 2020
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Ingår i: Progress in nuclear energy (New series). - : Elsevier BV. - 0149-1970 .- 1878-4224. ; 125
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Tidskriftsartikel (refereegranskat)abstract
- Nondestructive gamma-ray spectrometry of nuclear fuel is routinely performed in axial gamma scanning devices and more recently with gamma emission tomography. Following the irradiation of a fresh nuclear fuel with high intensity neutron flux in a nuclear reactor core, a great number of gamma-emitting radionuclides are created. These can be utilized for gamma spectrometric techniques. However, due to the high density and atomic number of the nuclear fuel, self-attenuation of gamma-rays is a challenge, which requires attenuation correction in order to perform accurate analysis of the source activity in the fuel.In this study, the degradation of the gamma-ray mass attenuation with burnup was investigated and, in addition, a predictive model was created by investigating the attenuation change at various gamma energies caused by the burnup of the nuclear fuel. This model is intended for use by spectrometry practitioners inspecting nuclear fuel. To this aim, the energy-dependent gamma-ray mass-attenuation coefficients were investigated as a function of burnup for UOX, and three MOX fuels having different initial Pu contents. The Serpent 2 reactor physics code was used to simulate the burnup history of the fuel pins. The nuclide inventory of the Serpent 2 output is combined with the NIST XCOM database to calculate the mass attenuation coefficients.The mass attenuation coefficient of the fuel was found to decrease with the fuel burnup, in the range of a few percent, depending on the burnup and gamma energy. Also, a theoretical burnup dependent swelling model was imposed on fuel density to see how linear attenuation coefficient of fuel material is changed. Furthermore, greater effect may be expected on the transmitted intensity, where a simulation study of a PWR assembly revealed that the contribution from the inner rods in a scanned fuel assembly increased by tens of percent compared to the one with non-irradiated fresh fuels, when shielded by the outer rods of the assembly. A sensitivity analysis was performed in order to test the effect of a number of geometrical and operational reactor parameters that were considered to potentially effect the mass attenuation coefficient. Finally, a simple-to-use predictive model was constructed providing the mass-attenuation coefficient [cm2/g] of fuel as a function of burnup [MWd/kgHM] and initial Pu content [wt%]. The resulting predictive model was optimized by using the nonlinear regression method.
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| 11. |
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| 12. |
- Davour, Anna, et al.
(författare)
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Applying image analysis techniques to tomographic images of irradiated nuclear fuel assemblies
- 2016
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 96, s. 223-229
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a set of image analysis techniques used for extraction of information from cross-sectional images of nuclear fuel assemblies, achieved from gamma emission tomography measurements. These techniques are based on template matching, an established method for identifying objects with known properties in images.We demonstrate a rod template matching algorithm for identification and counting of the fuel rods present in the image. This technique may be applicable in nuclear safeguards inspections, because of the potential of verifying the presence of all fuel rods, or potentially discovering any that are missing.We also demonstrate the accurate determination of the position of a fuel assembly, or parts of the assembly, within the imaged area. Accurate knowledge of the assembly position enables detailed modelling of the gamma transport through the fuel, which in turn is needed to make tomographic reconstructions quantifying the activity in each fuel rod with high precision.Using the full gamma energy spectrum, details about the location of different gamma-emitting isotopes within the fuel assembly can be extracted. We also demonstrate the capability to determine the position of supporting parts of the nuclear fuel assembly through their attenuating effect on the gamma rays emitted from the fuel. Altogether this enhances the capabilities of non-destructive nuclear fuel characterization.
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| 13. |
- Dekker Nitert, Marloes, et al.
(författare)
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Impact of an Exercise Intervention on DNA Methylation in Skeletal Muscle From First-Degree Relatives of Patients With Type 2 Diabetes.
- 2012
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797.
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Tidskriftsartikel (refereegranskat)abstract
- To identify epigenetic patterns, which may predispose to type 2 diabetes (T2D) due to a family history (FH) of the disease, we analyzed DNA methylation genome-wide in skeletal muscle from individuals with (FH(+)) or without (FH(-)) an FH of T2D. We found differential DNA methylation of genes in biological pathways including mitogen-activated protein kinase (MAPK), insulin, and calcium signaling (P ≤ 0.007) and of individual genes with known function in muscle, including MAPK1, MYO18B, HOXC6, and the AMP-activated protein kinase subunit PRKAB1 in skeletal muscle of FH(+) compared with FH(-) men. We further validated our findings from FH(+) men in monozygotic twin pairs discordant for T2D, and 40% of 65 analyzed genes exhibited differential DNA methylation in muscle of both FH(+) men and diabetic twins. We further examined if a 6-month exercise intervention modifies the genome-wide DNA methylation pattern in skeletal muscle of the FH(+) and FH(-) individuals. DNA methylation of genes in retinol metabolism and calcium signaling pathways (P < 3 × 10(-6)) and with known functions in muscle and T2D including MEF2A, RUNX1, NDUFC2, and THADA decreased after exercise. Methylation of these human promoter regions suppressed reporter gene expression in vitro. In addition, both expression and methylation of several genes, i.e., ADIPOR1, BDKRB2, and TRIB1, changed after exercise. These findings provide new insights into how genetic background and environment can alter the human epigenome.
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| 14. |
- Favalli, Andrea, et al.
(författare)
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Determining initial enrichment, burnup, and cooling time of pressurized-water-reactor spent fuel assemblies by analyzing passive gamma spectra measured at the Clab interim-fuel storage facility in Sweden
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 820, s. 102-111
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the Next Generation Safeguards Initiative (NGSI)–Spent Fuel (SF) project is to strengthen the technical toolkit of safeguards inspectors and/or other interested parties. The NGSI–SF team is working to achieve the following technical goals more easily and efficiently than in the past using nondestructive assay measurements of spent fuel assemblies: (1) verify the initial enrichment, burnup, and cooling time of facility declaration; (2) detect the diversion or replacement of pins; (3) estimate the plutonium mass [which is also a function of the variables in (1)]; (4) estimate the decay heat; and (5) determine the reactivity of spent fuel assemblies. Since August 2013, a set of measurement campaigns has been conducted at the Central Interim Storage Facility for Spent Nuclear Fuel (Clab), in collaboration with Swedish Nuclear Fuel and Waste Management Company (SKB). One purpose of the measurement campaigns was to acquire passive gamma spectra with high-purity germanium and lanthanum bromide scintillation detectors from Pressurized Water Reactor and Boiling Water Reactor spent fuel assemblies. The absolute 137Cs count rate and the 154Eu/137Cs, 134Cs/137Cs, 106Ru/137Cs, and 144Ce/137Cs isotopic ratios were extracted; these values were used to construct corresponding model functions (which describe each measured quantity’s behavior over various combinations of burnup, cooling time, and initial enrichment) and then were used to determine those same quantities in each measured spent fuel assembly. The results obtained in comparison with the operator declared values, as well as the methodology developed, are discussed in detail in the paper.
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| 15. |
- Grogan, B., et al.
(författare)
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NDA Measurement Analysis of Spent Nuclear Fuel Assemblies at the SwedishClab Facility Using the INDEPTH Code
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A project to research the application of non-destructive assay (NDA) to spent fuel assemblies is underwayamong a team comprised of the European Commission, DG Energy, Directorate Safeguards; the SwedishNuclear Fuel and Waste Management Company; Uppsala University; and US national laboratories (LosAlamos National Laboratory, Lawrence Livermore National Laboratory, and Oak Ride NationalLaboratory). The research goals of this project combine safeguards goals (detection of missing/substitutedfuel pins and verification of operator declarations) and non-safeguards goals (estimation of decay heat andreactivity of each assembly). The final objective of this project is to quantify the capability of severalintegrated NDA instruments being developed to meet the aforementioned safeguards and non-safeguardsgoals using combined signatures of neutron, gamma-ray, and decay heat.In support of these goals, passive gamma and neutron measurements were made on 50 spent fuelassemblies at the Swedish Central Interim Storage Facility for Spent Nuclear Fuel (Clab) using high-purity germanium and Fork detectors. The Oak Ridge National Laboratory (ORNL) Inverse DepletionTheory (INDEPTH) code was used to reconstruct the spent fuel parameters (initial enrichment, burnup,and cooling time) for each assembly. INDEPTH uses a gradient-based search technique—combined withthe ORIGEN code for forward depletion calculations—to find the spent fuel parameters that result inpassive gamma and neutron outputs that best match the measurements. The results of the INDEPTHcalculations are presented and compared to the operator declarations (trusted in this case) in order toassess how accurately these parameters can be determined using current passive gamma and neutronmeasurements. These results will provide a baseline which can be used to assess whether and by howmuch new safeguards instruments being developed for NDA measurements can improve the accuracy ofreconstructed fuel parameter values.
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| 16. |
- Hellesen, Carl, 1980-, et al.
(författare)
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Nuclear Spent Fuel Parameter Determination using Multivariate Analysis of Fission Product Gamma Spectra
- 2017
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 110, s. 886-895
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate the application of multivariate data analysis methods to the analysis of gamma spectroscopy measurements of spent nuclear fuel (SNF). Using a simulated irradiation and cooling of nuclear fuel over a wide range of cooling times (CT), total burnup at discharge (BU) and initial enrichments (IE) we investigate the possibilities of using a multivariate data analysis of the gamma ray emission signatures from the fuel to determine these fuel parameters. This is accomplished by training a multivariate analysis method on simulated data and then applying the method to simulated, but perturbed, data.We find that for SNF with CT less than about 20 years, a single gamma spectrum from a high resolution gamma spectrometer, such as a high-purity germanium spectrometer, allows for the determination of the above mentioned fuel parameters.Further, using measured gamma spectra from real SNF from Swedish pressurized light water reactors we were able to confirm the operator declared fuel parameters. In this case, a multivariate analysis trained on simulated data and applied to real data was used.
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| 17. |
- Hellesen, Carl, et al.
(författare)
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Transient Simulation of Gas Bubble in a Medium Sized Lead Cooled Fast Reactor
- 2014
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Ingår i: Proceedings of the International Conference on Physics of Reactors (PHYSOR 2014).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A common problem for many liquid metal cooled fast reactor designs is the positive void worth of the coolant. In this context, an advantage of lead cooled fast reactors is the high temperature of coolant boiling. In contrast to sodium cooled fast reactors this, in practice, precludes coolant boiling. However, partial voiding of the core could result from e.g. gas bubbles entering the core from below. This would introduce a positive reactivity, if the bubble is large enough. In this paper we model this type of event using a point kinetics code coupled to a heat transport code. The reactivity parameters are obtained from a Monte Carlo code. The 300 MWth reactor design Alfred is used as a test case. We show that in general the reactor design studied is robust in such events, and we conclude that small bubbles a measureable Power oscillation would occur. For very large bubbles there exist a possibility of core damage. The cladding is the most sensitive part.
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| 18. |
- Ingvander, Susanne, 1979-
(författare)
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Snow particle size investigations using digital image analysis - implications for ground observations and remote sensing of snow
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the past century climate warming has caused rapid changes in the Cryosphere. This has increased the need to accurately monitor rates of change in snow and ice in remote or sparsely populated areas where environmental observing capacity is limited. Monitoring snow cover requires understanding of the snow pack and the snow surface attributes. Snow particle size is an important parameter for characterization of snow pack properties. The size and shape of the snow particles affects the snow/air-ratio which in turn affect how energy is reflected on the snow surface. This governs the snow pack energy balance by changing the albedo or backscattering properties of the snow. Both the albedo and the snow particle size can be quantified by remote sensing. However, the snow particle size estimated by remote sensing, also called the optically equivalent particle size, represents only an approximation of the true or physical particle size of snow. Thus, there is demand for methods that relate both parameters and help to improve the interpretation of remote sensing data of snow at higher spatial and temporal scales. To address this demand the aim of this dissertation thesis is to improve existing sampling methods of the physical snow particle size to retrieve high-resolution, spatial and temporal data sets for validation of remote sensing data. A field sampling method based on object-oriented analysis of digital images was developed that allows measurements of various snow particle size parameters such as length, width, area, specific surface area and shape. The method generates a continuous snow particle size distribution that supports the detailed statistical characterization of a large number of samples. The results show its possibility to compare data from different existing methods. The sampling method was applied in field sites in Antarctica and in northern Sweden, to characterize the spatial variability in the physical snow particle size and to estimate correlations between various remote sensing products and the observed physical snow particle size. The results of the presented studies show that more detailed measurements of snow particle size in the field at higher temporal and spatial scales can improve the interpretation of active and passive satellite retrieved data.
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| 19. |
- Jacobsson, Staffan, 1970-, et al.
(författare)
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Outcomes of the JNT 1955 Phase I Viability Study of Gamma Emission Tomography for Spent Fuel Verification
- 2017
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Ingår i: ESARDA Bulletin. - 1977-5296. ; :55, s. 10-28
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Tidskriftsartikel (refereegranskat)abstract
- The potential for gamma emission tomography (GET) to detect partial defects within a spent nuclear fuel assembly has been assessed within the IAEA Support Program project JNT 1955, phase I, which was completed and reported to the IAEA in October 2016. Two safeguards verification objectives were identified in the project; (1) independent determination of the number of active pins that are present in a measured assembly, in the absence of a priori information about the assembly; and (2) quantitative assessment of pin-by-pin properties, for example the activity of key isotopes or pin attributes such as cooling time and relative burnup, under the assumption that basic fuel parameters (e.g., assembly type and nominal fuel composition) are known. The efficacy of GET to meet these two verification objectives was evaluated across a range of fuel types, burnups and cooling times, while targeting a total interrogation time of less than 60 minutes.The evaluations were founded on a modelling and analysis framework applied to existing and emerging GET instrument designs. Monte Carlo models of different fuel types were used to produce simulated tomographer responses to large populations of "virtual" fuel assemblies. The simulated instrument response data were then processed using a variety of tomographic-reconstruction and image- processing methods, and scoring metrics were defined and used to evaluate the performance of the methods.This paper describes the analysis framework and metrics used to predict tomographer performance. It also presents the design of a "universal" GET (UGET) instrument intended to support the full range of verification scenarios envisioned by the IAEA. Finally, it gives examples of the expected partial-defect detection capabilities for some fuels and diversion scenarios, and it provides a comparison of predicted performance for the notional UGET design and an optimized variant of an existing IAEA instrument.
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| 20. |
- Jacobsson Svärd, Staffan, 1970-, et al.
(författare)
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Tomographic determination of spent fuel assembly pin-wise burnup and cooling time for detection of anomalies
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The IAEA has initiated Member States’ Support Program project JNT A 1955 to assess the partial defect detection capabilities of gamma emission tomography (GET) for spent nuclear fuel assembly verification. The GET technique is based on measurements of the gamma-ray flux distribution around a spent fuel assembly using dedicated, tomographic equipment and subsequent reconstruction of the internal source distribution using tomographic algorithms applied on the recorded data. One of the verification objectives identified for the project is the quantitative measurement of pin-by-pin properties, e.g. burnup and/or cooling time, for the detection of anomalies and/or verification of operator-declared data. For this objective, reconstruction algorithms that return quantitative, isotopic pin-by-pin data are applied.Previously, GET measurements performed on commercial nuclear fuel assemblies in Sweden have proven capable of determining the relative pin-by-pin power distribution with high precision in BWR fuel with short cooling time, based on the measured distribution of the gamma-ray emitting fission product 140Ba/La in the fuel. In the current project, the capabilities of GET to determine additional pin-wise fuel parameters in additional fuel types are being assessed. The evaluations are based on Monte Carlo simulations of the emission of gamma-rays from the fuel and their detection in a tomographic measurement device.This paper describes the algorithms used for reconstructing quantitative pin-wise data and the results that are anticipated with this technique. It is argued that detailed modelling of the gamma-ray attenuation through the highly inhomogeneous mix of strongly-attenuating fuel rods and less-attenuating surrounding water (wet storage) or air (dry storage) is required to yield high precision in the reconstructed data. The burnup distribution assessment would be based on the recording of 662-keV gamma radiation from 137Cs, whereas the assessment of both burnup and cooling time simultaneously requires the GET measurement and pin-wise reconstruction of at least two isotopes, which puts constraints on the measurement equipment used.
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| 21. |
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| 22. |
- Jansson, Peter, 1971-, et al.
(författare)
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A new methodology for thermal analysis of geological disposal of spent nuclear fuel using integrated simulations of gamma heating and finite element modeling
- 2022
-
Ingår i: Annals of Nuclear Energy. - : Elsevier. - 0306-4549 .- 1873-2100. ; 172
-
Tidskriftsartikel (refereegranskat)abstract
- A new methodology is illustrated, where the evolution of temperature in a geological disposal system for spent nuclear fuel is estimated by integrated calculations of a spatially distributed gamma heating source with conventional finite element thermal transport modeling. A case with one canister loaded with fuel assemblies with a cooling time of 30 years in a KBS-3 type repository illustrates the methodology. For this particular case, the effect of including distributed gamma heating rate in the modeling has a small impact on the temperature distribution compared to the conventional case of heat generated locally in the canister, resulting in a small decrease of the maximum temperature in the canister. A large proportion of gamma heating occurs inside the outer boundary of the copper canister for this case. Other potential consequences of radiation escaping the canister are discussed.
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| 23. |
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| 24. |
- Jansson, Peter, et al.
(författare)
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Blind Benchmark Exercise for Spent Nuclear Fuel Decay Heat
- 2022
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Ingår i: Nuclear science and engineering. - : Informa UK Limited. - 0029-5639 .- 1943-748X. ; 196:9, s. 1125-1145
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Tidskriftsartikel (refereegranskat)abstract
- The decay heat rate of five spent nuclear fuel assemblies of the pressurized water reactor type were measured by calorimetry at the interim storage for spent nuclear fuel in Sweden. Calculations of the decay heat rate of the five assemblies were performed by 20 organizations using different codes and nuclear data libraries resulting in 31 results for each assembly, spanning most of the current state-of-the-art practice. The calculations were based on a selected subset of information, such as reactor operating history and fuel assembly properties. The relative difference between the measured and average calculated decay heat rate ranged from 0.6% to 3.3% for the five assemblies. The standard deviation of these relative differences ranged from 1.9% to 2.4%.
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| 25. |
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| 26. |
- Jansson, Peter, 1971-, et al.
(författare)
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Monte Carlo simulations of a Universal Gamma-Ray Emission Tomography Device
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A design of a universal gamma-ray emission tomography (UGET) device has been definedwithin the IAEA MSSP project JNT1955 in order to evaluate partial defect detectioncapabilities when using tomography on used nuclear fuel assemblies. The design isintended to allow for fuel assembly verification using single photon emission tomographyon a broad range of fuel assembly types and fuel parameters.In this paper, results from a set of Monte Carlo radiation transport simulations for the UGETdesign are presented. In these simulations, two cases are studied, each of them with a PWR fuel, in one case the complete fuel assembly and in the other with 11 missing rods.The characteristic features of the design are presented including expected performancerequirements on the gamma-ray collimator and detector system, supported by thesimulation results. In addition, the agreement between the two simulation tools used, Geant4 and MCNP, indicate that any of the two can give satisfactory accuracy for this purpose.
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| 27. |
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| 28. |
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| 29. |
- Kanoni, Stavroula, et al.
(författare)
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Analysis with the exome array identifies multiple new independent variants in lipid loci
- 2016
-
Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 25:18, s. 4094-4106
-
Tidskriftsartikel (refereegranskat)abstract
- It has been hypothesized that low frequency (1-5% minor allele frequency (MAF)) and rare (<1% MAF) variants with large effect sizes may contribute to the missing heritability in complex traits. Here, we report an association analysis of lipid traits (total cholesterol, LDL-cholesterol, HDL-cholesterol triglycerides) in up to 27 312 individuals with a comprehensive set of low frequency coding variants (ExomeChip), combined with conditional analysis in the known lipid loci. No new locus reached genome-wide significance. However, we found a new lead variant in 26 known lipid association regions of which 16 were >1000-fold more significant than the previous sentinel variant and not in close LD (six had MAF <5%). Furthermore, conditional analysis revealed multiple independent signals (ranging from 1 to 5) in a third of the 98 lipid loci tested, including rare variants. Addition of our novel associations resulted in between 1.5- and 2.5-fold increase in the proportion of heritability explained for the different lipid traits. Our findings suggest that rare coding variants contribute to the genetic architecture of lipid traits.
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| 30. |
- Kyrpides, Nikos C, et al.
(författare)
-
Genomic encyclopedia of bacteria and archaea: sequencing a myriad of type strains.
- 2014
-
Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1545-7885. ; 12:8
-
Tidskriftsartikel (refereegranskat)abstract
- Microbes hold the key to life. They hold the secrets to our past (as the descendants of the earliest forms of life) and the prospects for our future (as we mine their genes for solutions to some of the planet's most pressing problems, from global warming to antibiotic resistance). However, the piecemeal approach that has defined efforts to study microbial genetic diversity for over 20 years and in over 30,000 genome projects risks squandering that promise. These efforts have covered less than 20% of the diversity of the cultured archaeal and bacterial species, which represent just 15% of the overall known prokaryotic diversity. Here we call for the funding of a systematic effort to produce a comprehensive genomic catalog of all cultured Bacteria and Archaea by sequencing, where available, the type strain of each species with a validly published name (currently∼11,000). This effort will provide an unprecedented level of coverage of our planet's genetic diversity, allow for the large-scale discovery of novel genes and functions, and lead to an improved understanding of microbial evolution and function in the environment.
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| 31. |
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| 32. |
- Lyth, Johan, 1980-, et al.
(författare)
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Trends in cutaneous malignant melanoma in Sweden 1997-2011: Thinner tumours and improved survival among men
- 2015
-
Ingår i: British Journal of Dermatology. - : Wiley-Blackwell. - 0007-0963 .- 1365-2133. ; 172:3, s. 700-706
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Both patient survival and the proportion of patients diagnosed with thin cutaneous malignant melanoma (CMM) have been steadily rising in Sweden as in most western countries, though the rate of improvement in survival appears to have declined in Sweden at the end of last millennium.Objectives: To analyse the most recent trends in the distribution of tumour thickness (T-category) as well as CMM-specific survival in Swedish patients diagnosed 1997-2011.Methods: This nationwide population-based study included 30 590 patients registered in the Swedish Melanoma Register (SMR) and diagnosed with a first primary invasive CMM 1997-2011. The patients were followed through 2012 in the national Cause-of-Death Register.Results: Logistic and Cox regression analyses adjusting for age at diagnosis, tumour site, and health care region were carried out. The odds ratio for being diagnosed with thicker tumours was significantly reduced (P = 0·0008) and the CMM-specific survival significantly improved in men diagnosed 2007-2011 compared to men diagnosed 1997-2001 (hazard ratio=0·81; 95% CI 0·72-0·91, P = 0·0009) while the corresponding differences for women were not significant. Women were diagnosed with significantly thicker tumours during 2002-2006 and a tendency towards decreased survival was observed compared to those diagnosed earlier 1997-2001 and later 2007-2011.Conclusion: In Sweden, the CMMs of men are detected earlier over time and this seems to be followed by an improved CMM-specific survival for men. Women are still diagnosed with considerably thinner tumours and they experience a better survival than men.
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| 33. |
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| 34. |
- Moore, Peter L., et al.
(författare)
-
Effect of a cold margin on ice flow at the terminus of Storglaciären, Sweden : implications for sediment transport
- 2011
-
Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 57:201, s. 77-87
-
Tidskriftsartikel (refereegranskat)abstract
- The cold-based termini of polythermal glaciers are usually assumed to adhere strongly toan immobile substrate and thereby supply significant resistance to the flow of warm-based ice upglacier.This compressive environment is commonly thought to uplift basal sediment to the surface ofthe glacier by folding and thrust faulting. We present model and field evidence from the terminus ofStorglaci¨aren, Sweden, showing that the cold margin provides limited resistance to flow from up-glacier.Ice temperatures indicate that basal freezing occurs in this zone at 10−1 –10−2 ma−1, but model resultsindicate that basal motion at rates greater than 1ma−1 must, nevertheless, persist there for surface andbasal velocities to be consistent with measurements. Estimated longitudinal compressive stresses of 20–25 kPa within the terminus further indicate that basal resistance offered by the cold-based terminusis small. These results indicate that where polythermal glaciers are underlain by unlithified sediments,ice-flow trajectories and sediment transport pathways may be affected by subglacial topography andhydrology more than by the basal thermal regime
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| 35. |
- Moore, Peter L., et al.
(författare)
-
Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden
- 2013
-
Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 42:1, s. 71-83
-
Tidskriftsartikel (refereegranskat)abstract
- Internal structure, stable isotope composition and tritium concentration were measured in and around debrisbearingice at the margin of Storglaciären, where englacial debris bands have previously been inferred to form bythrusting. Two types of debris bands were distinguished: (i) an unsorted diamicton band that is laterally continuousfor more than 200 m, and (ii) well-sorted sand and gravel bands that are lenticular and discontinuous.Above-background tritium levels and enrichment of d18O and dD in ice from the diamicton band indicateentrainment by basal freeze-on since 1952. Isotopic enrichment and tritium-free ice in the sandy debris bands alsoindicate entrainment in freezing water, but prior to 1952. The lenticular cross-section, sorting and stratification ofthe sandy bands suggest that they were deposited englacially. The basally accreted diamicton band has beenelevated tens of metres above the bed and presently overlies the englacially deposited sandy bands, suggesting thatthe stratigraphy has been disrupted. Three interpretations could account for these observations: (i) thrusting offast-moving ice over slow, marginal ice uplifting recently accreted basal ice along the fault; (ii) folding near themargin, elevating young basal ice over older basal and englacial ice; and (iii) debris-band formation by anunknown mechanism and subsequent contamination of ice geochemical properties by meltwater flow throughdebris bands. Although none of these interpretations is consistent with all measurements, folding is mostcompatible with observations and local ice-flow kinematics.
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| 36. |
- Nicolas, Aude, et al.
(författare)
-
Genome-wide Analyses Identify KIF5A as a Novel ALS Gene
- 2018
-
Ingår i: Neuron. - : Cell Press. - 0896-6273 .- 1097-4199. ; 97:6, s. 1268-1283.e6
-
Tidskriftsartikel (refereegranskat)abstract
- To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.
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| 37. |
- Rantakokko, Jouni, et al.
(författare)
-
Positioning of emergency personnel in rescue operations :
- 2007
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Summary and recommendations Presently, GPS-equipped mobile phones are launched at a large scale, enabling a variety of positioning based services. Indeed, GPS is expected to be the future killer application for mobile phones and services. The concept of accurate positioning by technical means implies a large number of applications not only for the mass market, but also for rescue services, fire brigades, police forces, and military and so on. For professional and governmental safety-of-life services the current systems are far from usable and large efforts have to be concentrated on research and development. Technologies based on GPS and other satellite-based positioning systems alone are vulnerable and are expected to malfunction in indoor or challenging electromagnetic environments, or due to antagonistic measures. Satellite-based positioning is a key component in a robust communication and positioning system aimed for first responders. Satellite based positioning in combination with local radio-based positioning systems and dead-reckoning or inertial navigation systems are enablers to fulfill the users? requirements on accuracy and availability of the positioning service. Sweden is a competent player within security. Around 300 companies with some 22.000 employees have been identified within the area. Swedish industry, research institutes and universities are expected to take part in international consortiums within EU FP7, as well as being a player within DHS funded research and development within the personal positioning and navigation area. The market potential for professional and safety-of-life personal equipment for robust positioning and communication with suitable means for information presentation is significant. In the US and the EU there are some 2 million incident responders each. On a national level we count some 35.000 fire fighters, police, and military personnel in international operations. A migration of the technology to private end-consumers as implemented in consumer electronics opens up a gigantic market for wireless services within navigation, gaming, and position-awareness services. Within the project positioning of first responders in rescue operations, robust positioning has been studied. From a system perspective, technologies for positioning of personnel are key system components within a platform for positioning, information transfer for command and control, and information processing and presentation for the personnel at all levels. \? Systems for training are needed to introduce the end-user to the technology, and for training and simulation of novel strategies enabled by the technology. Stationary training systems can be implemented with state-of-the art positioning methods. Feedback from the end-user to the R&D community is instrumental in the specification and development of future means for positioning of first responders. A research infrastructure, or test-bed, for implementation and evaluation of robust positioning is an essential tool. \? The functionality of the equipment has to be robust against hostile electromagnetic environments, either due to the actual physical environment (indoor scenario, intersystem interference from nearby electronic equipment, scenario within a large steel constructions, or power plant, etc), or due to electronic warfare antagonistic actions. Research has to be performed in several areas such as channel characterization for radio positioning, quality of satellite signals subjected to interference, and integrity of sensor information due to external influences. \? Contemporary MEMS-technology provides small-size sensors with low energy consumption. The rapid development within sensor technologies enables data fusion from a plurality of sensors by digital signal processing. Fundamental issues within digital signal processing have to be studied in several fields, including methods to enhance sensor performance by incorporating behavioral modeling; fusion of digital information from a plurality of sensors; aspects of hardware implementation to fulfill requirements on size, weight and uptime, and software defined receivers for radio-based positioning, communication and mapping. In summary, future systems for positioning of first responders in rescue operations rely on the development of infra-structure aimed for end-users in a training scenario; and a platform for R&D-purposes. In parallel, fundamental issues have to be studied regarding the electromagnetic environment, as well as methodologies in digital signal processing.
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| 38. |
- Rathore, Vikram, et al.
(författare)
-
Calculation of Spatial Response of a Collimated Segmented HPGe detector for Gamma Emission Tomography by MCNP Simulations
- 2022
-
Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 69:4, s. 714-721
-
Tidskriftsartikel (refereegranskat)abstract
- We have proposed a planar electronically segmented HPGe detector concept in combination with a multi-slit collimator for gamma emission tomography. In this work, the spatial resolution achievable by using the collimated segmented HPGe detector was evaluated, prior to the manufacture and operation of the detector. The spatial response of a collimated segmented HPGe detector concept was evaluated using simulations performed with Monte Carlo N-Particle transport code MCNP6. The full detector and multi-slit collimator system were modeled and for the quantification of the spatial response, the Modulation Transfer Function (MTF) was chosen as a performance metric. The MTF curve was obtained through the calculation of the Line Spread Function (LSF) by analyzing simulated projection data. In addition, tomographic reconstructions of the simulated simplified test objects were made to demonstrate the performance of the segmented HPGe detector in the planned application. For 662 keV photons, the spatial resolution obtained was approximately the same as the collimator slit width for both 100 and 150 mm long collimators. The corresponding spatial resolution at 1596 keV photon energy was almost twice the slit width for 100 mm collimator, due to the partial penetration of the high-energy gamma rays through the collimator bulk. For a 150 mm long collimator, an improved resolution was obtained.
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| 39. |
- Rathore, Vikram, et al.
(författare)
-
Geometrical optimisation of a segmented HPGe detector for spectroscopic gamma emission tomography : A simulation study
- 2021
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 998
-
Tidskriftsartikel (refereegranskat)abstract
- Segmented coaxial HPGe (High Purity Germanium) detectors have recently been shown to be feasible for Gamma Emission Tomography (GET). This type of detector allows for a combination of high efficiency and high energy resolution in gamma spectrometry of irradiated nuclear fuel. The ultimate aim of developing segmented HPGe for GET measurements is to achieve a high spatial resolution to facilitate imaging of rod-internal features and interrogation of smaller irradiated fuel samples.In this work, we present the optimisation of a segmented HPGe detector through a simulation study using the Monte Carlo particle transport code MCNP. Constraints to each dimension of the detector were identified, from manufacturing limitations and requirements arising from the use of a finite-sized collimator slit. In particular, a relationship between the minimum inner radius of the coaxial detector and the segments azimuthal dimension was derived based on the identified constraints. Segment azimuthal and radial dimensions have been varied (based on the derived relationship between the azimuthal and radial dimension) and the full energy efficiency and misidentification rate were evaluated to obtain the optimal dimensions. The optimal ranges of the segment dimensions were determined.
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| 40. |
- Rubino, Stefano, 1978-, et al.
(författare)
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In-situ contacting of nanosheets and remote EMCD
- 2009
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Ingår i: 2nd International Workshop on Remote Electron Microscopy and In Situ Studies, Gothenburg, Sweden 16-18 November 2009.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 41. |
- Rudbeck Jepsen, Martin, et al.
(författare)
-
Transitions in European land-management regimes between 1800 and 2010
- 2015
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Ingår i: Land use policy. - : Elsevier BV. - 0264-8377 .- 1873-5754. ; 49:SI, s. 53-64
-
Tidskriftsartikel (refereegranskat)abstract
- Land use is a cornerstone of human civilization, but also intrinsically linked to many global sustainability challenges—from climate change to food security to the ongoing biodiversity crisis. Understanding the underlying technological, institutional and economic drivers of land-use change, and how they play out in different environmental, socio-economic and cultural contexts, is therefore important for identifying effective policies to successfully address these challenges. In this regard, much can be learned from studying long-term land-use change. We examined the evolution of European land management over the past 200 years with the aim of identifying (1) key episodes of changes in land management, and (2) their underlying technological, institutional and economic drivers. To do so, we generated narratives elaborating on the drivers of land use-change at the country level for 28 countries in Europe. We qualitatively grouped drivers into land-management regimes, and compared changes in management regimes across Europe. Our results allowed discerning seven land-management regimes, and highlighted marked heterogeneity regarding the types of management regimes occurring in a particular country, the timing and prevalence of regimes, and the conditions that result in observed bifurcations. However, we also found strong similarities across countries in the timing of certain land-management regime shifts, often in relation to institutional reforms (e.g., changes in EU agrarian policies or the emergence and collapse of the Soviet land management paradigm) or to technological innovations (e.g., drainage pipes, tillage and harvesting machinery, motorization, and synthetic fertilizers). Land reforms frequently triggered changes in land management, and the location and timing of reforms had substantial impacts on land-use outcomes. Finally, forest protection policies and voluntary cooperatives were important drivers of land-management changes. Overall, our results demonstrate that land-system changes should not be conceived as unidirectional developments following predefined trajectories, but rather as path-dependent processes that may be affected by various drivers, including sudden events.
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| 42. |
- Sannel, A. Britta K., 1968-
(författare)
-
Holocene dynamics in subarctic peat plateaus of west-central Canada : Vegetation succession, peat accumulation and permafrost history
- 2007
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dynamics in vegetation, permafrost and peat and net carbon accumulation rates throughout the Holocene have been studied in two subarctic peat plateaus of west-central Canada through plant macrofossil analysis, geochemical analyses and AMS radiocarbon dating. Peatland formation at the studied sites began around 6600-5900 cal yr BP as a result of paludification of upland forests. Permafrost aggradation probably occurred 5600-4500 cal yr BP when Sphagnum fuscum became established and rootlet layers started to appear. Alternating layers of Sphagnum fuscum and rootlet peat throughout most of the peat profiles are indicating relatively dry surface conditions, suggesting that permafrost conditions have remained stable since the peat plateau stages were initiated. Local fires have occurred in the peatlands, but most fires did not cause degradation of the permafrost. However, lower peat and net carbon accumulation rates are recorded from rootlet layers containing charcoal. The long-term peat and net carbon accumulation rates for both studied peat profiles are 0,30-0,31 mm/yr and 12,5-12,7 gC/m2yr. Accumulation rates are variable depending on peat plateau stage. Peat accumulation rates are in general 4-5 times higher in S. fuscum than in rootlet stages, and net carbon accumulation rates are 3-4 times higher. Therefore even though Sphagnum peat makes up a majority of the peat profile depth, rootlet peat stages can represent most of the time since the peatland was initiated. The gross stratigraphy and plant macrofossil analyses show that there have been no wet phases, indicating permafrost collapse, since the peat plateau stages were initiated. This suggests that subarctic peat plateaus with alternating Sphagnum fuscum and rootlet peat layers have been acting as long-term net carbon sinks, accumulating carbon which has been incorporated into the permafrost, throughout most of the Holocene. High and stable carbon/nitrogen ratios throughout most of the profiles suggest that decomposition has not occurred in the perennially frozen peat. Since the peat plateaus are characterized by no decay in the permafrost and dry surface conditions, methane emissions are negligible from these ecosystems. In a future warmer climate carbon that has been stored under permafrost conditions can be remobilized. The warming may cause drier surface conditions resulting in increased emissions of carbon dioxide or, alternatively, permafrost collapse resulting in wetter surface conditions and increased methane emissions.
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| 43. |
- Sannel, A. Britta K., et al.
(författare)
-
Permafrost Warming in a Subarctic Peatland - Which Meteorological Controls are Most Important?
- 2016
-
Ingår i: Permafrost and Periglacial Processes. - : Wiley. - 1045-6740 .- 1099-1530. ; 27:2, s. 177-188
-
Tidskriftsartikel (refereegranskat)abstract
- Because climate change can affect the carbon balance and hydrology in permafrost peatlands, a better understanding of their sensitivity to changes in temperature and precipitation is needed. In Tavvavuoma, northernmost Sweden, meteorological parameters and ground thermal properties have been monitored in a peat plateau from 2006 to 2013. During this time period, the air temperature record shows no warming trend, and the late-season thaw depth has been relatively stable at around 55-60cm. Meanwhile, the mean annual ground temperature at 1m depth has increased by 0.06 degrees C/yr and at 2-5m depth the permafrost is currently warmer than -0.3 degrees C. Statistical analyses suggest that interannual changes in thaw depth and ground temperatures are affected by different meteorological factors. Summer air temperatures and annual thawing degree-days control thaw depth (p0.05), whereas winter precipitation/snow depth affects ground temperatures (p0.1). The permafrost in this peat plateau is likely relict and not in equilibrium with current climatic conditions. Since the early 20(th) century, there has been a regional increase in air temperature and snow depth. If the ongoing permafrost warming in Tavvavuoma is a result of these long-term trends, short-term variability in meteorological parameters can still have an impact on the rate of permafrost degradation, but unless pronounced climate cooling occurs, thawing of the peat plateau is inevitable.
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| 44. |
- Sannel, A. Britta K., 1968-
(författare)
-
Temporal and spatial dynamics in subarctic peat plateaus and thermokarst lakes
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Permafrost peatlands are widespread at high northern latitudes and are important soil organic carbon reservoirs. A future warming in these areas, as suggested by global climate models, can cause thawing and increased ground subsidence (thermokarst), resulting in changes in surface hydrology and ecosystem functioning. The aim of this thesis is to increase our knowledge of temporal and spatial dynamics in subarctic peat plateaus with interspersed thermokarst lakes in order to better understand how these ecosystems respond to climate change. Detailed plant macrofossil and carbon/nitrogen ratio analyses of two peat plateaus located in the continuous and northern discontinuous permafrost zones in west-central Canada show that permafrost conditions have been stable since permafrost developed around 5600–4500 cal yr BP. Peat plateaus act as carbon sinks over time. The lack of wet phases since the plateaus formed, despite several local fires, suggests that this type of peatlands have been negligible as methane sources throughout most of their history, representing a negative net radiative forcing on climate. Thermokarst lakes are common features in peat plateaus across the northern permafrost region. A time-series analysis of aerial photographs and high resolution satellite images in three peat plateau/thermokarst lake complexes along a climatic and permafrost gradient shows that where the mean annual air temperature (MAAT) is below -5ºC and ground temperatures are -2ºC or colder, only minor changes in thermokarst lake extent have occurred from the mid 1970s until the mid 2000s. During the same time interval extensive lake drainage and new lake formation has taken place where the MAAT is ca -3ºC and the ground temperature is close to 0ºC. In a future progressively warmer and wetter climate, permafrost degradation can cause significant impacts on landscape pattern and greenhouse gas exchange also in the vast peat plateaus presently experiencing stable permafrost conditions.
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| 45. |
- Scott, Robert A., et al.
(författare)
-
A genomic approach to therapeutic target validation identifies a glucose-lowering GLP1R variant protective for coronary heart disease
- 2016
-
Ingår i: Science Translational Medicine. - : American Association for the Advancement of Science (AAAS). - 1946-6234 .- 1946-6242. ; 8:341
-
Tidskriftsartikel (refereegranskat)abstract
- Regulatory authorities have indicated that new drugs to treat type 2 diabetes (T2D) should not be associated with an unacceptable increase in cardiovascular risk. Human genetics may be able to guide development of antidiabetic therapies by predicting cardiovascular and other health endpoints. We therefore investigated the association of variants in six genes that encode drug targets for obesity or T2D with a range of metabolic traits in up to 11,806 individuals by targeted exome sequencing and follow-up in 39,979 individuals by targeted genotyping, with additional in silico follow-up in consortia. We used these data to first compare associations of variants in genes encoding drug targets with the effects of pharmacological manipulation of those targets in clinical trials. We then tested the association of those variants with disease outcomes, including coronary heart disease, to predict cardiovascular safety of these agents. A low-frequency missense variant (Ala316Thr; rs10305492) in the gene encoding glucagon-like peptide-1 receptor (GLP1R), the target of GLP1R agonists, was associated with lower fasting glucose and T2D risk, consistent with GLP1R agonist therapies. The minor allele was also associated with protection against heart disease, thus providing evidence that GLP1R agonists are not likely to be associated with an unacceptable increase in cardiovascular risk. Our results provide an encouraging signal that these agents may be associated with benefit, a question currently being addressed in randomized controlled trials. Genetic variants associated with metabolic traits and multiple disease outcomes can be used to validate therapeutic targets at an early stage in the drug development process.
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| 46. |
- Senis, Lorenzo, et al.
(författare)
-
A computational methodology for estimating the detected energy spectra of the gamma-ray flux from irradiated nuclear fuel
- 2022
-
Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 69:4, s. 703-713
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray spectrometry using collimated detectors is a well-established examination method for irradiated nuclear fuel. However, the feasibility of examining a particular nuclide of interest is subject to constraints; the peak must be statistically determinable with the desired precision and the total spectrum count rate in the detector should not cause throughput issues. Methods were assembled for gamma spectrum prediction to optimize instruments for gamma emission tomography and to enable a priori feasibility evaluation of determination of single peaks of irradiated nuclear fuel. The aim was to find reliable results (~10% accuracy) regarding total spectrum and peak count rates with faster computation time than a full-Monte Carlo approach. For this purpose, the method is based on depletion calculations with SERPENT2, a point-source kernel method for the collimator response, a rig response matrix and a detector response matrix, both computed with MCNP6. The computational methodology uses as input the fuel properties (dimensions, materials, power history, and cooling time), and the instrumental setup (collimator and detector dimensions and materials). The prediction method was validated using measured data from a high-burnup, short-cooled test fuel rodlet from the Halden reactor. Absolute count rates and ratios of characteristic peaks were compared between predicted and measured spectra, showing a total count rate overestimation of 7% and discrepancies between 2-20% for the single peaks (same order of magnitude of the uncertainty). This level of agreement is deemed sufficient for measurement campaigns planning, and the optimization of spectroscopic instruments for use in gamma scanning and tomography of nuclear fuel.
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| 47. |
- Senis, Lorenzo, et al.
(författare)
-
Evaluation of gamma-ray transmission through rectangular collimator slits for application in nuclear fuel spectrometry
- 2021
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 1014
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray spectrometry is widely applied in several science fields, and in particular in non-destructive gamma scanning and gamma emission tomography of irradiated nuclear fuel. Often, a collimator is used in the experimental setup, to selectively interrogate a region of interest in the fuel. For the optimization of instrument design, as well as for planning measurement campaigns, predictive models for the transmitted gamma-ray intensity through the collimator are needed. Commonly, Monte Carlo Radiation Transport tools are used for accurate prediction of gamma-ray transport, however, the long computation time requirements when used in low-efficiency experimental setups present challenges.In this work, the full-energy peak intensity transmitted through a rectangular collimator slit was examined. A uniform planar surface source emitting isotropically was considered, and the rate of photons reaching an ideal counter plane on the opposite side of the collimator was evaluated by analytical integration. To find a closed-form primitive function, some idealizations were required, and thereby parametric models were obtained for the optical field of view, dependent on slit dimensions (length, height and width) and source-to-collimator distance. It was shown that the count rate in the detector is independent of the collimator-to-source distance. For contributions from outside the optical field of view, where a closed-form expression cannot be found, instead fast numerical integration methods were proposed.The results were validated using the Monte Carlo code MCNP6. For the analytical method, deviations were larger, the shorter the collimator, with up to 25% of underestimation obtained for the shortest examined collimator of 10 cm length. However, the longer the collimator, the better the observed agreement. This accuracy is deemed to be sufficient for instrument design and measurement planning, where often the order of magnitude of the count rate is not a priori known. For the numerical method, the results showed an agreement within 3 % for all evaluated collimator settings. The methods are planned for use in iterative optimization routines in the design of Gamma Emission Tomography devices, as well as for the prediction of gamma spectra obtained in the planning of fuel inspections. An application of the proposed method was demonstrated in spectrum prediction for a short cooling-time fuel rod test from the Halden reactor.
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| 48. |
- Senis, Lorenzo, et al.
(författare)
-
Feasibility study of gamma-ray micro-densitometry for the examination of nuclear fuel swelling
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Nuclear fuel undergoes several thermo-mechanical changes during irradiation in a nuclear reactor, such as change of density, caused by solid and gaseous swelling. This affects the heat transport within the pellet and, when leading to the pellet-cladding gap closure, it also affects the gap conductance, causing stress in the cladding. The density of irradiated fuel pellets can be measured in post-irradiation examination using several methods. In this work, a feasibility study was made using the gamma-ray transmission micro-densitometry technique. This is based on the comparison of two intensity measurements, with and without a sample with well-characterized thickness. Using a collimated source, a local examination of the density can be performed, scanning a pellet slice radially. The proposed technique aims to obtain a spatial resolution of cca. 100 microns. In this work, the parameters of the setup, such as the source activity, detector counting time, slit dimensions, collimator length, and sample thickness, are used to predict detector efficiency and expected count rates. The obtainable precision of the density is assessed by first-order uncertainty propagation of counting errors in the gamma-ray detection to the density estimate. A collimator design was presented that achieves a reasonable compromise between time requirements, precision, and spatial resolution. The sensitivity of the performance to set-up parameters was investigated. In addition, a realistic setup was modeled in MCNP6 for validation of the peak count-rate, and to ensure that the total spectrum count-rate is within typical throughput capabilities of HPGe detectors. The MCNP model was also used to confirm that the assumed attenuation law is valid in a relevant geometry, and to assess the spatial resolution, using the 10-90% edge spread of an Edge Spread Function. It is concluded that fuel density can be determined with <1 % precision, using a 100-micron wide slit, and 1 hour of measurement.
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| 49. |
- Sidstedt, Maja, et al.
(författare)
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Ultrasensitive sequencing of STR markers utilizing unique molecular identifiers and the SiMSen-Seq method
- 2024
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Ingår i: Forensic Science International: Genetics. - : Elsevier Ireland Ltd. - 1872-4973 .- 1878-0326. ; 71
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Tidskriftsartikel (refereegranskat)abstract
- Massively parallel sequencing (MPS) is increasingly applied in forensic short tandem repeat (STR) analysis. The presence of stutter artefacts and other PCR or sequencing errors in the MPS-STR data partly limits the detection of low DNA amounts, e.g., in complex mixtures. Unique molecular identifiers (UMIs) have been applied in several scientific fields to reduce noise in sequencing. UMIs consist of a stretch of random nucleotides, a unique barcode for each starting DNA molecule, that is incorporated in the DNA template using either ligation or PCR. The barcode is used to generate consensus reads, thus removing errors. The SiMSen-Seq (Simple, multiplexed, PCR-based barcoding of DNA for sensitive mutation detection using sequencing) method relies on PCR-based introduction of UMIs and includes a sophisticated hairpin design to reduce unspecific primer binding as well as PCR protocol adjustments to further optimize the reaction. In this study, SiMSen-Seq is applied to develop a proof-of-concept seven STR multiplex for MPS library preparation and an associated bioinformatics pipeline. Additionally, machine learning (ML) models were evaluated to further improve UMI allele calling. Overall, the seven STR multiplex resulted in complete detection and concordant alleles for 47 single-source samples at 1 ng input DNA as well as for low-template samples at 62.5 pg input DNA. For twelve challenging mixtures with minor contributions of 10 pg to 150 pg and ratios of 1–15% relative to the major donor, 99.2% of the expected alleles were detected by applying the UMIs in combination with an ML filter. The main impact of UMIs was a substantially lowered number of artefacts as well as reduced stutter ratios, which were generally below 5% of the parental allele. In conclusion, UMI-based STR sequencing opens new means for improved analysis of challenging crime scene samples including complex mixtures.
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| 50. |
- Smith, Eric L., et al.
(författare)
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A Viability Study of Gamma Emission Tomography for Spent Fuel Verification : JNT 1955 Phase I Technical Report
- 2016
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Rapport (refereegranskat)abstract
- The potential for gamma emission tomography (GET) to detect partial defects within a spent nuclear fuel assembly is being assessed through a collaboration of Support Programs to the International Atomic Energy Agency (IAEA). In the first phase of this study, two safeguards verification objectives have been identified. The first is the independent determination of the number of active pins that are present in the assembly, in the absence of a priori information about the assembly. The second objective is to provide quantitative assay of pin-by-pin properties, for example the activity of key isotopes or pin attributes such as cooling time and relative burnup, under the assumption that basic fuel parameters (e.g., assembly type and nominal fuel composition) are known. The efficacy of GET to meet these two verification objectives has been evaluated across a range of fuel types, burnups, and cooling times, and with a target total interrogation time of less than 60 minutes. This evaluation of GET viability for safeguards applications was founded on a modelling and analysis framework applied to existing and emerging GET instrument designs. Monte Carlo models of different fuel types were used to produce simulated tomographer responses to large populations of “virtual” fuel assemblies. Instrument response data were processed using a variety of tomographic-reconstruction and image-processing methods, and scoring metrics specific to each of the verification objectives were used to predict performance. This report describes the analysis framework and metrics used to predict tomographer performance, the design of a “universal” GET (UGET) instrument intended to support the full range of verification scenarios envisioned by the IAEA, and a comparison of predicted performance for the notional UGET design and an optimized variant of an existing IAEA instrument.
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