Browsing by Subject "COEFFICIENT"

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  • Lehtomaa, Jaakko; Resnick, Sidney (2020)
    One of the central objectives of modern risk management is to find a set of risks where the probability of multiple simultaneous catastrophic events is negligible. That is, risks are taken only when their joint behavior seems sufficiently independent. This paper aims to identify asymptotically independent risks by providing tools for describing dependence structures of multiple risks when the individual risks can obtain very large values. The study is performed in the setting of multivariate regular variation. We show how asymptotic independence is connected to properties of the support of the angular measure and present an asymptotically consistent estimator of the support. The estimator generalizes to any dimension N >= 2 and requires no prior knowledge of the support. The validity of the support estimate can be rigorously tested under mild assumptions by an asymptotically normal test statistic. (C) 2020 Elsevier B.V. All rights reserved.
  • Loimu, Venla; Seppälä, Tiina; Kapanen, Mika; Tuomikoski, Laura; Nurmi, Heidi; Makitie, Antti; Tenhunen, Mikko; Saarilahti, Kauko (2017)
    Background and purposes: Permanent xerostomia as a result of radiation-induced salivary gland damage remains a common side effect of radiotherapy (RT) of the head and neck. The purpose of this study was to evaluate the usefulness of diffusion-weighted magnetic resonance imaging (DW-MRI) in assessing the post-RT salivary gland function in patients with head and neck cancer (HNC). Materials and methods: In this prospective study, 20 HNC patients scheduled for bilateral neck chemoradiotherapy (CRT) with weekly cisplatin went through diffusion-weighted magnetic resonance imaging (DW-MRI) and salivary gland scintigraphy (SGS) prior to and at a mean of six months after completing the treatment. The changes in apparent diffusion coefficient (ADC) before and after treatment were compared with ejection fraction (EF) measured with SGS and the radiation dose absorbed by the salivary glands. Results: As a result of gustatory stimulation with ascorbic acid, the ADC showed a biphasic response with an initial increase and subsequent decrease. This pattern was seen both before and after RT. Post-RT ADC increased as a function of RT dose absorbed by the salivary glands. A moderate statistical correlation between pre- and post-RT ADCs at rest and EF measured with SGS was found. Conclusions: DW-MRI seems a promising tool for detection of physiological and functional changes in major salivary glands after RT. (C) 2016 Elsevier Ireland Ltd. All rights reserved.
  • Kask, Gilber; Uimonen, Mikko M.; Barner-Rasmussen, Ian; Tukiainen, Erkki J.; Blomqvist, Carl; Repo, Jussi P. (2021)
    The most widely used patient-reported outcome (PRO) measure for soft tissue sarcoma (STS) patients is the Toronto Extremity Salvage Score (TESS). The aim of the study was to validate and test the reliability of the TESS for patients with lower extremity STS based on Finnish population data. Patients were assessed using the TESS, the QLQ-C30 Function and Quality of life (QoL) modules, the 15D and the Musculoskeletal tumour Society (MSTS) score. The TESS was completed twice with a 2- to 4-week interval. The intraclass correlation coefficient (ICC) was used for test-retest reliability. Construct validity was tested for structural validity and convergent validity. Altogether 136 patients completed the TESS. A ceiling effect was noted as 21% of the patients scored maximum points. The ICC between first and second administration of the TESS was 0.96. The results of exploratory factor analysis together with high Cronbach's alpha (0.98) supported a unidimensional structure. The TESS correlated moderately with the MSTS score (rho = 0.59, p < 0.001) and strongly with the mobility dimension in the 15D HRQL instrument (rho = 0.76, p < 0.001) and the physical function in QLQ-C30 (rho = 0.83, p < 0.001). The TESS instrument is a comprehensive and reliable PRO measure. The TESS may be used as a validated single index score, for lower extremity STS patients for the measurement of a functional outcome. The TESS seems to reflect patients' HRQoL well after the treatment of lower extremity soft tissue sarcomas. (C) 2020 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
  • Virkkula, A.; Chi, X.; Ding, A.; Shen, Y.; Nie, W.; Qi, X.; Zheng, L.; Huang, X.; Xie, Y.; Wang, J.; Petäjä, T.; Kulmala, Markku (2015)
    Aerosol optical properties were measured with a seven-wavelength aethalometer and a three-wavelength nephelometer at the suburban site SORPES in Nanjing, China, in September 2013-January 2015. The aethalometer compensation parameter k, calculated with the Virkkula et al. (2007) method depended on the backscatter fraction, measured with an independent method, the integrating nephelometer. At lambda = 660 nm the daily averaged compensation parameter k approximate to 0.0017 +/- 0.0002 and 0.0042 +/- 0.0013 when backscatter fraction at lambda = 635 nm was in the ranges of 0.100 +/- 0.005 and 0.160 +/- 0.005, respectively. Also, the wavelength dependency of the compensation parameter depended on the backscatter fraction: when b(lambda = 525 nm) was less than approximately 0.13 the compensation parameter decreased with wavelength and at larger b it increased with wavelength. This dependency has not been considered in any of the algorithms that are currently used for processing aethalometer data. The compensation parameter also depended on the single-scattering albedo omega(0) so that k decreased with increasing omega(0). For the green light (lambda = 520 nm) in the omega(0) range 0.870 +/- 0.005, the average (+/- standard deviation) k approximate to 0.0047 +/- 0.006 and in the omega(0) range 0.960 +/- 0.005, k approximate to 0.0028 +/- 0.0007. This difference was larger for the near-infrared light (lambda = 880 nm): in the omega(0) range 0.860 +/- 0.005, k approximate to 0.0055 +/- 0.0023 and in the omega(0) range 0.960 +/- 0.005, k approximate to 0.0019 +/- 0.0011. The negative dependence of k on omega(0) was also shown with a simple theoretical analysis.
  • Ponkilainen, Ville T.; Häkkinen, Arja H.; Uimonen, Mikko M.; Tukiainen, Erkki; Sandelin, Henrik; Repo, Jussi P. (2019)
    The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a patient-reported outcome measure (PROM) that is widely used to evaluate the pain, stiffness, and physical function of patients with osteoarthritis of the hip and knee. Although the WOMAC has also been used for patients after foot and ankle surgery, it has not been validated for this purpose. A total of 130 patients with surgically treated ankle fractures completed the WOMAC, Visual Analogue Scale Foot and Ankle (VAS FA), Lower Extremity Functional Scale (LEFS), 15D Health-Related Quality-of-Life Questionnaire (15D), and Visual Analog Scale for General Health (VAS general health) after foot and ankle surgery. The structural validity of the WOMAC was assessed by using Cronbach's a, and convergent validity was tested between the WOMAC and reference outcome measures. Cronbach's a for the index score was 0.98 and 0.95, 0.86, and 0.98 for the Pain, Stiffness, and Physical Function subscales, respectively. The Spearman correlation coefficients were -0.84, -0.74, -0.58, and 0.55 for the VAS-FA, LEFS, 15D, and VAS general health, respectively. The relationships with the VAS-FA, LEFS, 15D, and VAS general health were strong. All relationships were statistically significant (p <.001). The WOMAC provides valid scores for assessing pain, stiffness, and physical function in patients having undergone ankle fracture surgery. (C) 2019 by the American College of Foot and Ankle Surgeons. All rights reserved.