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Sökning: L773:1873 1449

  • Resultat 1-10 av 17
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1.
  • Adamowicz, Tomasz, et al. (författare)
  • Regularity of p(.)-superharmonic functions, the Kellogg property and semiregular boundary points
  • 2014
  • Ingår i: Annales de l'Institut Henri Poincare. Analyse non linéar. - : Elsevier Masson / Institute Henri Poincar�. - 0294-1449 .- 1873-1430. ; 31:6, s. 1131-1153
  • Tidskriftsartikel (refereegranskat)abstract
    • We study various boundary and inner regularity questions for p(.)-(super)harmonic functions in Euclidean domains. In particular, we prove the Kellogg property and introduce a classification of boundary points for p(.)-harmonic functions into three disjoint classes: regular, semiregular and strongly irregular points. Regular and especially semiregular points are characterized in many ways. The discussion is illustrated by examples. Along the way, we present a removability result for bounded p(.)-harmonic functions and give some new characterizations of W-0(1,p(.)) spaces. We also show that p(.)-superharmonic functions are lower semicontinuously regularized, and characterize them in terms of lower semicontinuously regularized supersolutions.
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2.
  • Aleksanyan, Gohar, 1987- (författare)
  • Optimal regularity in the optimal switching problem
  • 2016
  • Ingår i: Annales de l'Institut Henri Poincare. Analyse non linéar. - : Elsevier. - 0294-1449 .- 1873-1430.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this article we study the optimal regularity for solutions to the following weakly coupled system with interconnected obstacles{min⁡(−Δu1+f1,u1−u2+ψ1)=0min⁡(−Δu2+f2,u2−u1+ψ2)=0 arising in the optimal switching problem with two modes. We derive the optimal C1,1-regularity for the minimal solution under the assumption that the zero loop set L:={ψ1+ψ2=0} is the closure of its interior. This result is optimal and we provide a counterexample showing that the C1,1-regularity does not hold without the assumption L=L0‾. 
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3.
  • Benedicks, Michael, et al. (författare)
  • Random perturbations and statistical properties of Henon-like maps
  • 2006
  • Ingår i: Annales de l'Institut Henri Poincare. Analyse non linéar. - 0294-1449 .- 1873-1430. ; 23:5, s. 713-752
  • Tidskriftsartikel (refereegranskat)abstract
    • For a large class of non-uniformly hyperbolic diffeomorphisms, we prove stochastic stability under small random noise: the unique stationary probability measure of the Markov chain converges to the Sinai-Ruelle-Bowen measure of the unperturbed attractor when the noise level tends to zero.
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4.
  • Carlsson Tedgren, Åsa, et al. (författare)
  • Comparison of high-dose-rate Ir-192 source strength measurements using equipment with traceability to different standards
  • 2014
  • Ingår i: Brachytherapy. - : Elsevier. - 1538-4721 .- 1873-1449. ; 13:4, s. 420-423
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE:According to the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism used for dose calculation in brachytherapy treatment planning systems, the absolute level of absorbed dose is determined through coupling with the measurable quantity air-kerma strength or the numerically equal reference air-kerma rate (RAKR). Traceability to established standards is important for accurate dosimetry in laying the ground for reliable comparisons of results and safety in adoption of new treatment protocols. The purpose of this work was to compare the source strength for a high-dose rate (HDR) (192)Ir source as measured using equipment traceable to different standard laboratories in Europe and the United States.METHODS AND MATERIALS:Source strength was determined for one HDR (192)Ir source using four independent systems, all with traceability to different primary or interim standards in the United States and Europe.RESULTS:The measured HDR (192)Ir source strengths varied by 0.8% and differed on average from the vendor value by 0.3%. Measurements with the well chambers were 0.5% ± 0.1% higher than the vendor-provided source strength. Measurements with the Farmer chamber were 0.7% lower than the average well chamber results and 0.2% lower than the vendor-provided source strength. All of these results were less than the reported source calibration uncertainties (k=2) of each measurement system.CONCLUSIONS:In view of the uncertainties in ion chamber calibration factors, the maximum difference in source strength found in this study is small and confirms the consistency between calibration standards in use for HDR (192)Ir brachytherapy.
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7.
  • Indrei, E., et al. (författare)
  • Regularity of solutions to fully nonlinear elliptic and parabolic free boundary problems
  • 2016
  • Ingår i: Annales de l'Institut Henri Poincare. Analyse non linéar. - : Elsevier. - 0294-1449 .- 1873-1430. ; 33:5, s. 1259-1277
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider fully nonlinear obstacle-type problems of the form. F(D2u,x)=f(x)a.e. in B1∩Ω,|D2u|≤Ka.e. in B1\Ω, where Ω is an open set and K>0. In particular, structural conditions on F are presented which ensure that W2,n(B1) solutions achieve the optimal C1,1(B1/2) regularity when f is Hölder continuous. Moreover, if f is positive on B-1, Lipschitz continuous, and u≠0⊂Ω, we obtain interior C1 regularity of the free boundary under a uniform thickness assumption on u=0. Lastly, we extend these results to the parabolic setting.
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8.
  • Karlsson, Johannes, et al. (författare)
  • Differences in outcome for cervical cancer patients treated with or without brachytherapy
  • 2017
  • Ingår i: Brachytherapy. - Philadelphia, USA : Elsevier. - 1538-4721 .- 1873-1449. ; 16:1, s. 133-140
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To compare the clinical outcome of cervical cancer patients treated with primary radiotherapy with and without the addition of brachytherapy.Methods and Materials: In all, 220 patients with cervical cancer stage I-IV treated between 1993 and 2009 were included. Three or five 6.0 Gy fractions of brachytherapy were given in addition to the external beam radiotherapy to 134 patients, whereas 86 patients received external beam radiotherapy alone (EBRTA). In the EBRTA group, the patients received external boost instead of brachytherapy with a total dose to the tumor of 64-72 Gy.Results: The 5-year overall survival and cancer-specific survival rates of the complete series were 42.5% and 55.5%, respectively. The rates of primary complete remission, 5-year cancer-specific survival, and recurrence were 92.5%, 68.5%, and 31.3% for the brachytherapy group vs. 73.3%, 35.4%, and 37.2% for the EBRTA group. The survival (all types) of the patients receiving brachytherapy was significantly (p < 0.0001) better than for the patients treated with external boost, but the difference was most pronounced in FIGO stage II tumors. Higher FIGO stage, nonsquamous cell carcinoma histology, treatment with EBRTA, and lower total equal 2-Gy (EQD2) external dose were significantly associated with poorer survival, lower rate of remission, and higher recurrence rate in multivariate models.Conclusions: Primary tumor remission rate, recurrence rate, and all types of survival rates were improved in the brachytherapy group. Brachytherapy is important to achieve sufficient doses to the periphery and central part of the tumor and should always be considered in treatment of cervical carcinomas.
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9.
  • Karlsson, Mattias, et al. (författare)
  • Monte Carlo dosimetry of the eye plaque design used at the St. Erik Eye Hospital for I-125 brachytherapy
  • 2014
  • Ingår i: Brachytherapy. - : Elsevier. - 1538-4721 .- 1873-1449. ; 13:6, s. 651-656
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: At St. Erik Eye Hospital in Stockholm, Sweden, ocular tumors of apical height above 6 mm are treated with brachytherapy, using iodine-125 seeds attached to a gold alloy plaque while the treatment planning is performed assuming homogeneous water surroundings. The aim of this work was to investigate the dose-modifying effects of the plaque and the seed fixating silicone rubber glue. METHODS AND MATERIALS: The impact of the gold plaque and silicone rubber glue was studied with the Monte Carlo N-particle transport code, version 5. RESULTS: For the 2 cm most proximal to the plaque surface along the plaques central axis, the eyeball received 104.6-93.0% of the dose in all-water conditions. CONCLUSIONS: The 0.3 mm thick layer of silicone rubber glue, used for seed fixation, attenuates photons little enough to allow characteristic X-rays from the gold alloy plaque to reach the eyeball. Close to the plaque, the dose rates were higher with the plaque and glue present, than in homogeneous water conditions. This is in contrast to what has been reported for more commonly used eye plaques, demonstrating the importance of investigating the dosimetry of individual treatment systems.
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10.
  • Lewis, John L., et al. (författare)
  • Regularity of flat free boundaries in two-phase problems for the p-Laplace operator
  • 2012
  • Ingår i: Annales de l'Institut Henri Poincare. Analyse non linéar. - 0294-1449 .- 1873-1430. ; 29:1, s. 83-108
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we continue the study in Lewis and Nystrom (2010) [19], concerning the regularity of the free boundary in a general two-phase free boundary problem for the p-Laplace operator, by proving regularity of the free boundary assuming that the free boundary is close to a Lipschitz graph.
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  • Resultat 1-10 av 17
  • [1]2Nästa

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