1. |
- Degago, S. A., et al.
(författare)
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Time- and stress-compressibility of clays during primary consolidation
- 2010
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Ingår i: Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE 2010, Trondheim, Norway, 2-4 June 2010. - : CRC Press. - 9780415592390 ; , s. 125-130
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Konferensbidrag (refereegranskat)abstract
- The existence of creep deformation during primary consolidation has been widely accepted; however, there are still contradicting opinions on the mechanisms that govern creep during the primary consolidation phase. This study aims to assess creep effects during primary consolidation such that it is possible to critically evaluate and challenge some of these opinions. A special type of interconnected oedometer tests were designed and conducted. The tests were numerically studied using a soil model based on the isotache concept. These analyses show that the isotache concept can capture the important features of the tests well and thereby describe the time- and stress-compressibility of a soil during the entire soil compression phase.
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- Degago, S.A., et al.
(författare)
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Use and misuse of the isotache concept with respect to creep hypotheses A and B
- 2011
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Ingår i: Geotechnique. - 0016-8505 .- 1751-7656. ; 61:10, s. 897-908
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Tidskriftsartikel (refereegranskat)abstract
- Time-dependent settlements of thick in situ clay layers are normally analysed based on results of thin laboratory specimens. However, the time used to complete primary consolidation is significantly different for laboratory specimens and in situ soil layers. Two totally different cases, referred to as creep hypotheses A and B, have been used as a basis of discussion to assess the effect of creep during the primary consolidation phase. Several laboratory and field experiments have been conducted to study the effect of soil layer thickness on the time-dependent compressibility of a soil layer. Some of these tests seemed to support hypothesis A, others hypothesis B, and in some cases showed a behaviour between the two. As a result this question has continued to be a controversial topic among researchers, and remains to be an issue that needs to be resolved. In this study, some relevant experimental investigations from the literature are thoroughly studied and critically reviewed, and also explained consistently using the isotache concept. This work indicates that the isotache approach can capture the main characteristics of the time-dependent compressibility of clays during both the primary and secondary consolidation phases. It is also shown that the misuse of the isotache concept, as reported in the literature, may give a confusing picture of reality. Based on the considered data, it is demonstrated that the measured time-dependent compressibility of clays agrees well with hypothesis B.
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3. |
- Esbjornsson, A-C, et al.
(författare)
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Ankle arthritis predicts polyarticular disease course and unfavourable outcome in children with juvenile idiopathic arthritis
- 2015
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Ingår i: Clinical and Experimental Rheumatology. - 0392-856X .- 1593-098X. ; 33:5, s. 751-757
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Tidskriftsartikel (refereegranskat)abstract
- Objective To evaluate the occurrence, clinical characteristics and prognostic factors associated with ankle arthritis in children with juvenile idiopathic arthritis (JIA). Methods 440 children with JIA were followed for eight years in a prospective Nordic population-based cohort study. Data on remission was available for 427 of these children. Occurrence of clinically assessed ankle arthritis was analysed in relation to JIA category, clinical characteristics and remission data eight years after disease onset. Results In 440 children with JIA, 251 (57%) experienced ankle arthritis during the first eight years of disease. Ankle arthritis was least common in the persistent oligoarticular category (25%) and most common in children with extended oligoarticular (83%) and polyarticular RF-negative (85%) JIA. Children who developed ankle arthritis during the first year of disease were younger at disease onset (median age 4.9 (IQR 2.1-8.8) vs. 6.6 (IQR 2.8-10.1) years, p<0.003) and had more cumulative affected joints at 8-year follow-up (median involved joints 10 (IQR 6-16) vs. 3 (IQR 2-9), p<0.001). The odds ratio for not achieving remission eight years after disease onset, if the ankle joint was involved during the first year of disease was 2.0 (95 %.0, p<0.001). Hind-, mid- and forefoot involvements were more common compared to patients without ankle arthritis. Conclusion In this Nordic population-based 8-year follow-up study, occurrence of ankle arthritis during the first year was associated with an unfavourable disease outcome. We suggest that ankle arthritis should be recognised in the assessment of prognosis and choice of treatment strategy in JIA.
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4. |
- Grimstad, G., et al.
(författare)
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Modeling creep and rate effects in structured anisotropic soft clays
- 2010
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Ingår i: Acta Geotechnica. ; 5:1, s. 69-81
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Tidskriftsartikel (refereegranskat)abstract
- In simulations of undrained triaxial tests, most soil models fail to capture the effect of post peak strain rate variation. This is due to the fact that no "swelling" is allowed for the viscoplastic volume strain. Imposing such restriction implies that dilative behavior cannot be modeled. Therefore, a model incorporating creep has been formulated using the so-called time resistance concept that uses a single creep parameter determined from an incremental oedometer test. The key feature of the proposed model is the introduction of the time resistance concept on the plastic multiplier rather than on the volumetric viscoplastic strain. This allows the viscoplastic volume strain to be either positive or negative depending on whether the state of the soil is on the "wet" or "dry" side of critical state line. The proposed model is based on an existing elastoplastic model for structured soft clay (S-CLAY1S). The paper gives a description of the constitutive model and the numerical scheme used in the implementation of the model. Capabilities of the model are illustrated with simulations of oedometer and triaxial tests. Results from such analyses show that the model is able to capture essential features of soft clay behavior.
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5. |
- Hinks, A, et al.
(författare)
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Fine-mapping the MHC locus in juvenile idiopathic arthritis (JIA) reveals genetic heterogeneity corresponding to distinct adult inflammatory arthritic diseases
- 2017
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Ingår i: Annals of the rheumatic diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 76:4, s. 765-772
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Tidskriftsartikel (refereegranskat)abstract
- Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases, comprising seven categories. Genetic data could potentially be used to help redefine JIA categories and improve the current classification system. The human leucocyte antigen (HLA) region is strongly associated with JIA. Fine-mapping of the region was performed to look for similarities and differences in HLA associations between the JIA categories and define correspondences with adult inflammatory arthritides.MethodsDense genotype data from the HLA region, from the Immunochip array for 5043 JIA cases and 14 390 controls, were used to impute single-nucleotide polymorphisms, HLA classical alleles and amino acids. Bivariate analysis was performed to investigate genetic correlation between the JIA categories. Conditional analysis was used to identify additional effects within the region. Comparison of the findings with those in adult inflammatory arthritic diseases was performed.ResultsWe identified category-specific associations and have demonstrated for the first time that rheumatoid factor (RF)-negative polyarticular JIA and oligoarticular JIA are genetically similar in their HLA associations. We also observe that each JIA category potentially has an adult counterpart. The RF-positive polyarthritis association at HLA-DRB1 amino acid at position 13 mirrors the association in adult seropositive rheumatoid arthritis (RA). Interestingly, the combined oligoarthritis and RF-negative polyarthritis dataset shares the same association with adult seronegative RA.ConclusionsThe findings suggest the value of using genetic data in helping to classify the categories of this heterogeneous disease. Mapping JIA categories to adult counterparts could enable shared knowledge of disease pathogenesis and aetiology and facilitate transition from paediatric to adult services.
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6. |
- Mikola, K., et al.
(författare)
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Transitioning patients with juvenile idiopathic arthritis to adult care: the Nordic experience
- 2022
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Ingår i: Pediatric Rheumatology. - : Springer Science and Business Media LLC. - 1546-0096. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- Background With juvenile idiopathic arthritis (JIA), there are several protocols and practices used worldwide for the transition from paediatric to adult care. In this study, we examined the transferral rates and disease activity after transition, as well as the disease- and health-related outcomes. We also introduce the transition practices employed in the Nordic countries. Methods The study population comprised 408 participants with a disease onset from 1997 to 2000 who attended an 18-year follow-up visit in this population-based Nordic JIA cohort study. The patients were retrospectively divided into three subgroups: Patients transferred directly from paediatric care to adult rheumatology care, patients referred there later, and patients never transferred during the 18-year follow-up period. Results One hundred and sixty-three (40%) JIA patients had been directly transferred to an adult clinic. The cumulative transition rate was 52%, but there were significant differences between the participating centres. Fifty patients had later been referred to an adult clinic. Among the 195 patients who had never been transferred, 39% were found to have disease activity at the study visit. Conclusion This study highlights the need to reconsider transition practices to avoid our undesirable finding of patients with disease activity in JIA, but no appropriate health care follow-up.
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7. |
- Nordal, E. B., et al.
(författare)
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Validity and predictive ability of the juvenile arthritis disease activity score based on CRP versus ESR in a Nordic population-based setting
- 2012
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 71:7, s. 1122-1127
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Tidskriftsartikel (refereegranskat)abstract
- Objective To compare the juvenile arthritis disease activity score (JADAS) based on C reactive protein (CRP) (JADAS-CRP) with JADAS based on erythrocyte sedimentation rate (ESR) (JADAS-ESR) and to validate JADAS in a population-based setting. Methods The CRP and ESR values and the corresponding JADAS scores (JADAS10/27/71) were compared in a longitudinal cohort study of 389 children newly diagnosed with juvenile idiopathic arthritis (JIA) in the Nordic JIA study. The construct validity and the discriminative and predictive ability of JADAS were assessed during a median disease course of 8 years by comparing JADAS with other measures of disease activity and outcome. Results At the first study visit the correlation between JADAS27-CRP and JADAS27-ESR was r = 0.99 whereas the correlation between CRP and ESR was r = 0.57. Children with higher JADAS scores had an increased risk of concomitant pain, physical disability and use of disease-modifying antirheumatic drugs (DMARDs). A higher JADAS score at the first study visit also significantly predicted physical disability, damage and no remission off medication at the final study visit, and also use of DMARDs during the disease course. Sensitivity to change, demonstrated as change in JADAS score compared with the American College of Rheumatology paediatric measures of improvement criteria, mostly showed excellent classification ability. Conclusion The JADAS-CRP and JADAS-ESR correlate closely, show similar test characteristics and are feasible and valid tools for assessing disease activity in JIA.
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8. |
- Nordal, E., et al.
(författare)
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Incidence and predictors of Uveitis in juvenile idiopathic arthritis in a Nordic long-term cohort study
- 2017
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Ingår i: Pediatric Rheumatology. - : Springer Science and Business Media LLC. - 1546-0096. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Background: The incidence of uveitis associated with juvenile idiopathic arthritis (JIA) varies around the world. Our aim was to investigate the incidence and predictors of uveitis in a Nordic population-based cohort. Methods: Consecutive JIA cases from defined geographical areas in Denmark, Finland, Sweden and Norway with disease onset between January 1997 to June 2000 were followed for median 98 months in this prospective longitudinal cohort study. Potential clinical and immunological predictors of uveitis were identified with logistic regression analysis. Results: Uveitis occurred in 89 (20.5%) of the 435 children with regular ophtalmologic follow-up among the 500 included. Chronic asymptomatic uveitis developed in 80 and acute symptomatic uveitis in 9 children. Uveitis developed at a median interval of 0.8 (range - 4.7 to 9.4) years after onset of arthritis. Predictors of uveitis were age < 7 years at JIA onset (Odds ratio (OR) 2.1, 95% confidence interval (CI) 1.3 to 3.5), presence of antihistone antibodies (AHA) > 15 U/ml (OR 4.8 (1.8 to 13.4)) and antinuclear antibodies (ANA) (OR 2.4 (1.5 to 4.0)). Mean combined IgM/IgG AHA was significantly higher in the uveitis group (19.2 U/ml) than in the non-uveitis group (10.2 U/ml) (p = 0.002). Young age at JIA onset predicted uveitis in girls (p < 0.001), but not in boys (p = 0.390). Conclusion: Early-onset arthritis and presence of AHA in girls, as well as presence of ANA in both genders, were significant predictors of chronic uveitis. The high incidence of uveitis in this long-term Nordic JIA cohort may have severe implications in a lifelong perspective.
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9. |
- Nordal, E., et al.
(författare)
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Participation in school and physical education in juvenile idiopathic arthritis in a Nordic long-term cohort study
- 2019
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Ingår i: Pediatric Rheumatology. - : Springer Science and Business Media LLC. - 1546-0096. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe aim of the study was to describe school attendance and participation in physical education in school among children with juvenile idiopathic arthritis (JIA).MethodsConsecutive cases of JIA from defined geographical areas of Finland, Sweden and Norway with disease onset in 1997 to 2000 were followed for 8 years in a multi-center cohort study, aimed to be as close to population-based as possible. Clinical characteristics and information on school attendance and participation in physical education (PE) were registered.ResultsParticipation in school and in PE was lowest initially and increased during the disease course. Eight years after disease onset 228/274 (83.2%) of the children reported no school absence due to JIA, while 16.8% reported absence during the last 2 months due to JIA. Full participation in PE was reported by 194/242 (80.2%), partly by 16.9%, and none by 2.9%. Lowest participation in PE was found among children with ERA and the undifferentiated categories. Absence in school and PE was associated with higher disease activity measures at the 8-year visit. School absence >1day at baseline predicted use of disease-modifying anti-rheumatic drugs, including biologics (DMARDs) (OR 1.2 (1.1-1.5)), and non-remission off medication (OR 1.4 (1.1-1.7) 8 years after disease onset.ConclusionSchool absence at baseline predicted adverse long-term outcome. In children and adolescents with JIA participation in school activities is mostly high after 8years of disease. For the minority with low participation, special attention is warranted to promote their full potential of social interaction and improve long-term outcome.
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