| 1. |
- Jacobsson Svärd, Staffan, 1972-, et al.
(författare)
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Gamma-ray Emission Tomography: Modelling and evaluation of partial-defect testing capabilities
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Assessment of gamma emission tomography (GET) for spent nuclear fuel verification is the task in IAEA MSP project JNT1955. In line with IAEA Safeguards R&D plan 2012-2023, the aim of this effort is to “develop more sensitive and less intrusive alternatives to existing NDA instruments to perform partial defect tests on spent fuel assemblies prior to transfer to difficult to access storage". The current viability study constitutes the first phase of three, with evaluation and decision points between each phase. Two verification objectives have been identified; (1) counting of fuel pins in tomographic images without any a priori knowledge of the fuel assembly under study, and (2) quantitative measurements of pin-by-pin properties, e.g. burnup, for the detection of anomalies and/or verification of operator-declared data.Previous measurements performed in Sweden and Finland have proven GET highly promising for detecting removed or substituted fuel pins (i.e. partial defects) in BWR and VVER-440 fuel assemblies even down to the individual fuel pin level. The current project adds to previous experiences by pursuing a quantitative assessment of the capabilities of GET for partial defect detection, across a broad range of potential IAEA applications, fuel types, and fuel parameters. A modelling and performance-evaluation framework has been developed to provide quantitative GET performance predictions, incorporating burn-up and cooling-time calculations, Monte Carlo radiation-transport and detector-response modelling, GET instrument definitions (existing and notional) and tomographic reconstruction algorithms, which use recorded gamma-ray intensities to produce cross-sectional images of the source distribution in the fuel assembly or conclusive pin-by-pin data. The framework also comprises image-processing algorithms and performance metrics that recognize the inherent trade-off between the probability of detecting missing pins and the false-alarm rate. Here, the modelling and analysis framework is described and preliminary results are presented.
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| 2. |
- Jansson, Peter, 1971-, et al.
(författare)
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Gamma Transport Calculations for Gamma Emission Tomography on Nuclear Fuel within the UGET Project
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The unattended gamma emission tomography (UGET) for spent nuclear fuel verification is an on-going project in the IAEA member states’ support program. In line with the long term R&D plan of the IAEA Department of Safeguards, it is anticipated that this effort will help develop “more sensitive and less intrusive alternatives to existing NDA instruments to perform partial defect test on spent fuel assembly prior to transfer to difficult to access storage”.In the first phase of the project, gamma transport calculations and modelling of exist- ing and proposed new designs of tomographic instruments is performed. In this paper, a set of Monte Carlo calculations regarding modelling of various tomographic devices are presented, including two existing tomographic instruments previously used for spent fuel measurements; one instrument based on scintillator detectors, developed by Uppsala University, and another based on CdTe detector arrays, developed by the JNT 1510 col- laborative effort (Hungary, Finland). Detailed models of the tomographic instruments, including structural materials, and the measured fuel assemblies are used in the simula- tions. The calculated results are compared to the experimentally measured data to provide a benchmark for the simulation procedure.The developed modelling capabilities are also used for evaluation of the partial-defect detection capabilities of the tomographic technique based on a proposed GET instrument design.
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| 3. |
- Nissen, Anna, 1981-
(författare)
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High Order Finite Difference Methods with Artificial Boundary Treatment in Quantum Dynamics
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The investigation of the dynamics of chemical reactions, both from the theoretical and experimental side, has drawn an increasing interest since Ahmed H. Zewail was awarded the 1999 Nobel Prize in Chemistry for his work on femtochemistry. On the experimental side, new techniques such as femtosecond lasers and attosecond lasers enable laser control of chemical reactions. Numerical simulations serve as a valuable complement to experimental techniques, not only for validation of experimental results, but also for simulation of processes that cannot be investigated through experiments. With increasing computer capacity, more and more physical phenomena fall within the range of what is possible to simulate. Also, the development of new, efficient numerical methods further increases the possibilities. The focus of this thesis is twofold; numerical methods for chemical reactions including dissociative states and methods that can deal with coexistence of spatial regions with very different physical properties. Dissociative chemical reactions are reactions where molecules break up into smaller components. The dissociation can occur spontaneously, e.g. by radioactive decay, or be induced by adding energy to the system, e.g. in terms of a laser field. Quantities of interest can for instance be the reaction probabilities of possible chemical reactions. This thesis discusses a boundary treatment model based on the perfectly matched layer (PML) approach to accurately describe dynamics of chemical reactions including dissociative states. The limitations of the method are investigated and errors introduced by the PML are quantified. The ability of a numerical method to adapt to different scales is important in the study of more complex chemical systems. One application of interest is long-range molecules, where the atoms are affected by chemical attractive forces that lead to fast movement in the region where they are close to each other and exhibits a relative motion of the atoms that is very slow in the long-range region. A numerical method that allows for spatial adaptivity is presented, based on the summation-by-parts-simultaneous approximation term (SBP-SAT) methodology. The accuracy and the robustness of the numerical method are investigated.
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| 4. |
- Svärd, Anna, et al.
(författare)
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A Comparison Between IgG- and IgA-class Antibodies to Cyclic Citrullinated Peptides and to Modified Citrullinated Vimentin in Early Rheumatoid Arthritis and Very Early Arthritis
- 2011
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Ingår i: Journal of Rheumatology. - : Journal of Rheumatology. - 0315-162X .- 1499-2752. ; 38:7, s. 1265-1272
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Because of their slightly higher sensitivity, it has been argued that antibodies to modified citrullinated vimentin (anti-MCV) are superior to antibodies to cyclic citrullinated peptides (anti-CCP), while others claim that anti-CCP is preferable because of higher diagnostic specificity for rheumatoid arthritis (RA). We evaluated IgG- and IgA-class anti-MCV and anti-CCP as diagnostic and prognostic markers in early arthritis. less thanbrgreater than less thanbrgreater thanMethods. Two Swedish arthritis populations were examined: 215 patients with early RA (andlt;= 12 months duration) from the Swedish TIRA-1 cohort, and 69 patients with very early arthritis (andlt;= 3 months duration) from the Kronoberg Arthritis Incidence cohort, in which 22% were diagnosed with RA. IgG anti-CCP and anti-MCV antibodies were analyzed with commercial kits. These tests were modified for IgA-class antibody detection. less thanbrgreater than less thanbrgreater thanResults were related to disease course, smoking habits, and shared epitope status. Results. In the TIRA-1 cohort, occurrence of IgG anti-MCV and IgG anti-CCP showed a 93% overlap, although IgG anti-MCV had higher diagnostic sensitivity. Twenty-four percent tested positive for IgA anti-MCV compared to 29% for IgA anti-CCP. In the Kronoberg Arthritis Incidence cohort, 15% tested positive for IgG anti-MCV and 6% for IgA anti-MCV, compared to 10% positive for IgG anti-CCP and 3% positive for IgA anti-CCP, revealing that anti-CCP had higher diagnostic specificity for RA. As previously reported for IgA anti-CCP, IgA anti-MCV antibodies occurred in a small proportion of high-level IgG antibody-positive sera and were associated with a more aggressive disease course. Smokers were more often positive for antibodies to citrullinated proteins, most strikingly among the patients who were IgA anti-MCV-positive. less thanbrgreater than less thanbrgreater thanConclusion. The occurrences of IgG-class anti-MCV and anti-CCP in early RA largely overlap. The sensitivity of anti-MCV is slightly higher, while the diagnostic specificity is higher for anti-CCP. In both instances a positive test predicts an unfavorable disease course, possibly slightly more so for anti-MCV. Although associated with a more active disease over time, IgA-class anti-CCP or anti-MCV do not add any diagnostic advantage.
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| 5. |
- Svärd, Anna, et al.
(författare)
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A disease-modifying role for mucosal IgA antibodies to citrullinated antigens?
- 2012
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ Publishing Group. - 0003-4967 .- 1468-2060. ; 71:Issue suppl. 1, s. A38-A39
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Tidskriftsartikel (refereegranskat)abstract
- Objective The aim of this study was to investigate whether immunoglobulin A (IgA) antibodies to cyclic citrullinated peptides CCP) can be detected in saliva of patients with established heumatoid arthritis (RA) and if it relates to clinical manifestations. Methods Salivary samples were collected (by ‘passive drooling’) from 63 consecutive patients with established RA at a visit to the rheumatology outpatient clinic (Falun, Sweden), and from 20 healthy persons (hospital staff). The samples were centrifuged and kept frozen at −70°C until analysis. IgA-class anti-CCP antibodies in saliva were analysed by adaptation of commercial ELISA (Immunoscan RA, Euro-Diagnostica AB, Malmo, Sweden) using polyclonal rabbit antihuman α-chain specific antibodies conjugated with horseradish peroxidase(DakoCytomation, Glostrup, Denmark) as secondary antibody. To ensure specificity of the reaction, a corresponding ELISA was set up to analyse IgA antibodies to control antigen(cyclic arginine peptide, CAP), and anti-CCP/anti-CAP ratios were calculated. Also, inhibition studies were performed by preincubation of sera with soluble CCP or CAP. Clinical and laboratory data on disease activity, that is, C reactive protein (CRP), erythrocyte sedimentation rate (ESR), and 28-joint count disease activity score (DAS28) as well as radiological outcome (occurrence or absence of erosions as judged by a radiologist in diagnostic routine) were achieved retrospectively via the patients’ medical records. Results Background reactivity against CCP was found in virtually all patients and healthy subjects, whereas a positive anti-CCP/anti-CAP ratio (≥1.5) was found in 14 out of 63 RA patients (22%) and in one healthy subject (5%). Salivary IgA-reactivity with CCP was dose-dependently inhibited by soluble CCP (but not with CAP) in sera with anti-CCP/anti- CAP ratios ≥1.5. No IgG-reactivity to CCP was found in saliva, although all patients with salivary IgA anti-CCP tested IgG anti-CCP-positive in serum. Furthermore, less than half of those testing IgA-positive in saliva were IgA anti-CCP positive in serum, strongly arguing against passive leakage of anti-CCP antibodies from blood to saliva. The patients testing positive for salivary IgA antibodies had lower average disease activity measures (CRP, ESR, DAS28) at presentation and fewer developed bony erosions within 6 years after presentation (p=0.043, Fisher’s exact test). Conclusion Salivary IgA antibodies to citrullinated proteins were found in a subset of IgG anti-CCP positive RA patients. In contrast to their serum counterparts, salivary IgA antibodies may associate with a milder/less destructive disease course. This accords with the notion that secretory IgA antibodies exert anti-inflammatory actions, and that they may be associated with induction of systemic tolerance (oral tolerance). The possible disease-modifying role of mucosal immunity to citrullinated proteins needs further investigation!
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| 6. |
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| 7. |
- Svärd, Anna, 1964-
(författare)
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Circulating and Mucosal Antibodies to Citrullinated Antigens in Rheumatoid Arthritis
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation and subsequent destruction of cartilage and bone. The etiology is largely unknown, although genetic as well as environmental factors are involved. The manifestations and consequences of RA differ between individuals. This makes it important to find early markers for the disease course, in order to enable the most suitable treatment. IgG antibodies to cyclic citrullinated peptides (CCP) have high specificity for RA, but only around 60% of RA patients test positive for IgG anti-CCP.The aim of this thesis was to evaluate the usefulness of serum IgA anti-CCP as a diagnostic maker compared to IgG anti-CCP, and to assess IgA versus IgG anti-CCP status in relation to smoking habits and genetic background. Another aim was to evaluate signs of mucosal immunization by analyzing salivary IgA anti-CCP.IgA anti-CCP was present in a subgroup of RA patients with high levels of IgG anti-CCP and a slightly more severe disease course. Similar results were found regarding IgA class antibodies to modified citrullinated vimentin (MCV). IgG anti-MCV had slightly higher sensitivity for RA than IgG anti-CCP, thus identifying a group of IgG anti-CCP negative patients with an unfavourable disease course. However, the lower diagnostic specificity of IgG anti-MCV limits its usefulness.Among 63 patients with established RA, salivary IgA anti-CCP was found in 22% and was associated with a more favourable outcome regarding erosive joint disease at follow-up. IgA anti-CCP in serum was strongly associated with smoking, and the earlier known interaction between smoking and shared epitope (SE) was here shown to be valid only for subjects positive for IgA anti-CCP in combination with IgG anti-CCP.In conclusion, IgG anti-CCP is still the most useful serologic marker of RA, but IgA anti-CCP should be further investigated as a prognostic marker. The association between smoking and IgA anti-CCP strongly indicates a pathogenic role for smoking and IgA anti-CCP, supporting the possibility that RA may originate from chronic airway irritation. The less erosive disease in patients positive for salivary IgA anti-CCP indicates a protective role of secretory IgA anti-CCP.
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| 8. |
- Svärd, Anna, et al.
(författare)
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Salivary IgA antibodies to cyclic citrullinated peptides (CCP) in rheumatoid arthritis
- 2013
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Ingår i: Immunobiology. - : Elsevier. - 0171-2985 .- 1878-3279. ; 218:2, s. 232-237
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Tidskriftsartikel (refereegranskat)abstract
- Circulating IgG anti-cyclic citrullinated peptide antibodies (CCP) are highly specific for rheumatoid arthritis (RA) and prognostic of poor outcome. Serum IgA anti-CCP occurs in a subset of IgG-positive cases and relates to still more aggressive disease. Mucosal IgA-class antibodies, however, are generally associated with anti-inflammatory actions and systemic tolerance induction. In the present study, unstimulated salivary samples from 63 patients with established RA and 20 healthy persons were analysed by enzyme-linked immunoassay for the presence of IgA anti-CCP antibodies. To ensure antigen specificity, IgA-reactivity with the corresponding uncitrullinated antigen, cyclic arginine peptide (CAP), was analysed and anti-CCP/anti-CAP ratios calculated. Retrospective data regarding disease activity and radiological outcome were achieved via medical records. Salivary IgA anti-CCP was found in 14/63 (22%) patients and one (5%) control (positive test = anti-CCP/anti-CAP ratio andgt; 1.5). Salivary IgA reactivity was dose-dependently inhibited by pre-incubation with soluble CCP to a degree strongly correlating with anti-CCP/anti-CAP ratio. In salivary IgA anti-CCP positive patients, joint erosions within 6 years of diagnosis was significantly lower (p = 0.043), and at the time for diagnosis there was a trend towards lower erythrocyte sedimentation rate (p = 0.071) and C-reactive protein (p = 0.085). Contrasting to circulating IgG and IgA anti-CCP, our results imply that salivary IgA antibodies may be associated with a less severe outcome of RA. Hypothetically, this relates to an anti-inflammatory and protective immunomodulating role of secretory IgA-class autoantibodies against citrullinated antigens presented at mucosal surfaces.
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