Knut Waagan

• Julsvoll, Elisabeth Heggem; Myhrvold, Birgitte Lawaetz; Waagan, Knut; Vøllestad, Nina Køpke & Robinson, Hilde Stendal (2024). Identifying phenotypes in persons with temporomandibular disorders using latent class analyses. Journal of Oral Rehabilitation. ISSN 0305-182X. doi: 10.1111/joor.13837. Fulltekst i vitenarkiv Vis sammendrag

  Background The heterogeneity of persons with temporomandibular disorders (TMD) and the lack of effective treatments have called for a biopsychosocial model and the development of a more personalised treatment approach. Emphasis on phenotypes might be a beneficial approach. Objective Identifying phenotypes among persons with TMD using potential prognostic factors, including personal characteristics and responses to clinical tests. Additionally, examining the distribution of TMD diagnoses within the identified phenotypes. Methods A cross-sectional study including 208 persons (85% females) seeking physiotherapy for problems in the temporomandibular area. All participants were examined clinically and answered questionnaires electronically. The phenotypes were identified using latent class analysis based on seven potential prognostic factors selected within pain, function and psychological domains. Table analysis was used to explore the distribution of TMD diagnoses within the identified phenotypes. Results Most participants fit into one of three identified phenotypes. Phenotype 1 (32%) was characterised by functional disability, low psychosocial scores and low risk for developing chronicity and future work disability; Phenotype 2 (29%) by parafunctional habits, low psychosocial score and seeking treatment to reduce pain; and Phenotype 3 (39%) by high levels of mental distress, fear avoidance and a large risk of future work disability. Intra-articular disorders dominated Phenotype 1, myalgia and TMD-related headache Phenotype 2, while Phenotype 3 included all the different TMD diagnoses. Conclusion The knowledge about the three identified phenotypes might be useful for clinicians treating persons with TMD and for the development of preventive strategies and more personalised treatment.

• Pavlović, Milena; Scheffer, Lonneke; Motwani, Keshav; Kanduri, Chakravarthi; Kompova, Radmila & Vazov, Nikolay Aleksandrov [Vis alle 42 forfattere av denne artikkelen] (2021). The immuneML ecosystem for machine learning analysis of adaptive immune receptor repertoires. Nature Machine Intelligence. 3(11), s. 936–944. doi: 10.1038/s42256-021-00413-z. Fulltekst i vitenarkiv
• Irgens, Pernille Marie; Myhrvold, Birgitte Lawaetz; Kongsted, Alice; Waagan, Knut; Engebretsen, Kaia Beck & Vøllestad, Nina Køpke [Vis alle 7 forfattere av denne artikkelen] (2021). The clinical course of neck pain: Are trajectory patterns stable over a 1-year period? European Journal of Pain. ISSN 1090-3801. s. 1–12. doi: 10.1002/ejp.1879. Fulltekst i vitenarkiv Vis sammendrag

  Background Recent studies with data-driven approaches have established common pain trajectories. It is uncertain whether these trajectory patterns are consistent over time, and if a shorter measurement period will provide accurate trajectories. Methods We included 1,124 patients with non-specific neck pain in chiropractic practice. We classified patients into pre-defined trajectory patterns in each of four quarters of the follow-up year (persistent, episodic, and recovery) based on measures of pain intensity and frequency from weekly SMS. We explored the shifts between patterns and compared patients with stable and shifting patterns on baseline characteristics and clinical findings. Results 785 (70%) patients were in the same pattern in 1st and 4th quarters. Patients with episodic pattern in the 1st quarter shifted to other patterns more frequently than patients in the other patterns. A stable persistent pattern was associated with reduced function and higher scores on psychosocial factors. There was a decreased frequency of patients classified as persistent pattern (75% to 63%) and an increase of patients in recovery pattern (4% to 15%) throughout the four quarters. The frequency of patients classified as episodic remained relatively stable (21% to 24%). Conclusions We found an overall stability of the persistent pattern, and that episodic patterns have more potential for shifts. Shifts mostly occurred between patterns closest in pain variation. The deviation in pattern distribution compared with previous studies suggests that the duration of measurement periods has an impact on the results of the classification. Significance Having persistent pain and having very minor pain is relatively stable over one year, while episodic pain has more potential for shifts. The duration of measurement periods appears to have an impact on the results of the classification. The given criteria resulted in a reduced frequency of episodic pattern due to shorter measurement periods. Our findings contribute to improved understanding and predicting NP using a combination of patient characteristics and trajectory patterns.

• Irgens, Pernille Marie; Kongsted, Alice; Myhrvold, Birgitte Lawaetz; Waagan, Knut; Engebretsen, Kaia Beck & Natvig, Bård [Vis alle 8 forfattere av denne artikkelen] (2020). Neck pain patterns and subgrouping based on weekly SMS-derived trajectories. BMC Musculoskeletal Disorders. 21, s. 1–14. doi: 10.1186/s12891-020-03660-0. Fulltekst i vitenarkiv Vis sammendrag

  Background Neck and low back pain represent dynamic conditions that change over time, often with an initial improvement after the onset of a new episode, followed by flare-ups or variations in intensity. Pain trajectories were previously defined based on longitudinal studies of temporal patterns and pain intensity of individuals with low back pain. In this study, we aimed to 1) investigate if the defined patterns and subgroups for low back pain were applicable to neck pain patients in chiropractic practice, 2) explore the robustness of the defined patterns, and 3) investigate if patients within the various patterns differ concerning characteristics and clinical findings. Methods Prospective cohort study including 1208 neck pain patients from chiropractic practice. Patients responded to weekly SMS-questions about pain intensity and frequency over 43 weeks. We categorized individual responses into four main patterns based on number of days with pain and variations in pain intensity, and subdivided each into four subgroups based on pain intensity, resulting in 16 trajectory subgroups. We compared baseline characteristics and clinical findings between patterns and between Persistent fluctuating and Episodic subgroups. Results All but two patients could be classified into one of the 16 subgroups, with 94% in the Persistent fluctuating or Episodic patterns. In the largest subgroup, “Mild Persistent fluctuating” (25%), mean (SD) pain intensity was 3.4 (0.6) and mean days with pain 130. Patients grouped as “Moderate Episodic” (24%) reported a mean pain intensity of 2.7 (0.6) and 39 days with pain. Eight of the 16 subgroups each contained less than 1% of the cohort. Patients in the Persistent fluctuating pattern scored higher than the other patterns in terms of reduced function and psychosocial factors. Conclusions The same subgroups seem to fit neck and low back pain patients, with pain that typically persists and varies in intensity or is episodic. Patients in a Persistent fluctuating pattern are more bothered by their pain than those in other patterns. The low back pain definitions can be used on patients with neck pain, but with the majority of patients classified into 8 subgroups, there seems to be a redundancy in the original model.

• LeVeque, Randall J.; Waagan, Knut; González, Frank I.; Rim, Donsub & Lin, Guang (2016). Generating Random Earthquake Events for Probabilistic Tsunami Hazard Assessment. Pure and Applied Geophysics (PAGEOPH). ISSN 0033-4553. doi: 10.1007/s00024-016-1357-1. Fulltekst i vitenarkiv Vis sammendrag

  To perform probabilistic tsunami hazard assessment for subduction zone earthquakes, it is necessary to start with a catalog of possible future events along with the annual probability of occurrence, or a probability distribution of such events that can be easily sampled. For near-field events, the distribution of slip on the fault can have a significant effect on the resulting tsunami. We present an approach to defining a probability distribution based on subdividing the fault geometry into many subfaults and prescribing a desired covariance matrix relating slip on one subfault to slip on any other subfault. The eigenvalues and eigenvectors of this matrix are then used to define a Karhunen-Loève expansion for random slip patterns. This is similar to a spectral representation of random slip based on Fourier series but conforms to a general fault geometry. We show that only a few terms in this series are needed to represent the features of the slip distribution that are most important in tsunami generation, first with a simple one-dimensional example where slip varies only in the down-dip direction and then on a portion of the Cascadia Subduction Zone.

• Fuchs, Franz Georg; McMurry, Andrew David; Mishra, Siddhartha; Risebro, Nils Henrik & Waagan, Knut (2011). Approximate Riemann Solvers and Robust High-Order Finite Volume Schemes for Multi-Dimensional Ideal MHD Equations. Communications in Computational Physics. ISSN 1815-2406. 9(2), s. 324–362. doi: 10.4208/cicp.171109.070510a. Fulltekst i vitenarkiv
• Fuchs, Franz Georg; McMurry, Andrew David; Mishra, Siddhartha & Waagan, Knut (2011). Simulating waves in the upper solar atmosphere with Surya: a well-balanced high-order finite-volume code. The Astrophysical Journal (ApJ). ISSN 0004-637X. 732(2), s. 75–75. doi: 10.1088/0004-637X/732/2/75. Fulltekst i vitenarkiv
• Fuchs, Franz Georg; McMurry, Andrew David; Mishra, Siddhartha; Risebro, Nils Henrik & Waagan, Knut (2010). Finite Volume Methods for Wave Propagation in Stratified Magneto-Atmospheres. Communications in Computational Physics. ISSN 1815-2406. 7(3), s. 403–638. doi: 10.4208/cicp.2009.08.154. Fulltekst i vitenarkiv
• Fuchs, Franz Georg; McMurry, Andrew David; Mishra, Siddhartha; Risebro, Nils Henrik & Waagan, Knut (2010). High order well-balanced finite volume schemes for simulating wave propagation in stratified magnetic atmospheres. Journal of Computational Physics. ISSN 0021-9991. 229(11), s. 4033–4058. doi: 10.1016/j.jcp.2010.01.038. Fulltekst i vitenarkiv
• Waagan, Knut (2008). Convergence rate of monotone numerical schemes for Hamilton-Jacobi equations with weak boundary conditions. SIAM Journal on Numerical Analysis. ISSN 0036-1429. 46(5), s. 2371–2392. doi: 10.1137/050632932. Fulltekst i vitenarkiv
• Bouchut, Francois; Klingenberg, Christian & Waagan, Knut (2007). A multiwave approximate Riemann solver for ideal MHD based on relaxation. I: theoretical framework. Numerische Mathematik. ISSN 0029-599X. 108(1), s. 7–42. Fulltekst i vitenarkiv
• Klingenberg, Christian; Schmidt, Wolfram & Waagan, Knut (2007). Numerical comparison of Riemann solvers for astrophysical hydrodynamics. Journal of Computational Physics. ISSN 0021-9991. 227(1), s. 12–35. Fulltekst i vitenarkiv

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• Waagan, Knut (2006). A numerical method for ideal magnetohydrodynamics based on relaxation. Fulltekst i vitenarkiv

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